text: // This is an open source non-commercial project. Dear PVS-Studio, please check
  // it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
  
  /*
   * ops.c: implementation of various operators: op_shift, op_delete, op_tilde,
   *        op_change, op_yank, do_put, do_join
   */
  
  #include <assert.h>
  #include <inttypes.h>
  #include <stdbool.h>
  #include <string.h>
  
  #include "nvim/vim.h"
  #include "nvim/ascii.h"
  #include "nvim/ops.h"
  #include "nvim/buffer.h"
  #include "nvim/change.h"
  #include "nvim/charset.h"
  #include "nvim/cursor.h"
  #include "nvim/assert.h"
  #include "nvim/edit.h"
  #include "nvim/eval.h"
  #include "nvim/eval/typval.h"
  #include "nvim/ex_cmds.h"
  #include "nvim/ex_cmds2.h"
  #include "nvim/ex_getln.h"
  #include "nvim/fileio.h"
  #include "nvim/fold.h"
  #include "nvim/getchar.h"
  #include "nvim/indent.h"
  #include "nvim/log.h"
  #include "nvim/mark.h"
  #include "nvim/extmark.h"
  #include "nvim/mbyte.h"
  #include "nvim/memline.h"
  #include "nvim/memory.h"
  #include "nvim/message.h"
  #include "nvim/misc1.h"
  #include "nvim/move.h"
  #include "nvim/normal.h"
  #include "nvim/option.h"
  #include "nvim/path.h"
  #include "nvim/screen.h"
  #include "nvim/search.h"
  #include "nvim/state.h"
  #include "nvim/strings.h"
  #include "nvim/terminal.h"
  #include "nvim/ui.h"
  #include "nvim/undo.h"
  #include "nvim/macros.h"
  #include "nvim/window.h"
  #include "nvim/lib/kvec.h"
  #include "nvim/os/input.h"
  #include "nvim/os/time.h"
  
  static yankreg_T y_regs[NUM_REGISTERS];
  
  static yankreg_T *y_previous = NULL; /* ptr to last written yankreg */
  
  // for behavior between start_batch_changes() and end_batch_changes())
  static int batch_change_count = 0;           // inside a script
  static bool clipboard_delay_update = false;  // delay clipboard update
  static bool clipboard_needs_update = false;  // clipboard was updated
  static bool clipboard_didwarn = false;
  
  /*
   * structure used by block_prep, op_delete and op_yank for blockwise operators
   * also op_change, op_shift, op_insert, op_replace - AKelly
   */
  struct block_def {
    int startspaces;              /* 'extra' cols before first char */
    int endspaces;                /* 'extra' cols after last char */
    int textlen;                  /* chars in block */
    char_u      *textstart;       /* pointer to 1st char (partially) in block */
    colnr_T textcol;              /* index of chars (partially) in block */
    colnr_T start_vcol;           /* start col of 1st char wholly inside block */
    colnr_T end_vcol;             /* start col of 1st char wholly after block */
    int is_short;                 /* TRUE if line is too short to fit in block */
    int is_MAX;                   /* TRUE if curswant==MAXCOL when starting */
    int is_oneChar;               /* TRUE if block within one character */
    int pre_whitesp;              /* screen cols of ws before block */
    int pre_whitesp_c;            /* chars of ws before block */
    colnr_T end_char_vcols;       /* number of vcols of post-block char */
    colnr_T start_char_vcols;       /* number of vcols of pre-block char */
  };
  
  #ifdef INCLUDE_GENERATED_DECLARATIONS
  # include "ops.c.generated.h"
  #endif
  
  // Flags for third item in "opchars".
  #define OPF_LINES  1  // operator always works on lines
  #define OPF_CHANGE 2  // operator changes text
  
  /*
   * The names of operators.
   * IMPORTANT: Index must correspond with defines in vim.h!!!
   * The third field indicates whether the operator always works on lines.
   */
  static char opchars[][3] =
  {
    { NUL, NUL, 0 },                       // OP_NOP
    { 'd', NUL, OPF_CHANGE },              // OP_DELETE
    { 'y', NUL, 0 },                       // OP_YANK
    { 'c', NUL, OPF_CHANGE },              // OP_CHANGE
    { '<', NUL, OPF_LINES | OPF_CHANGE },  // OP_LSHIFT
    { '>', NUL, OPF_LINES | OPF_CHANGE },  // OP_RSHIFT
    { '!', NUL, OPF_LINES | OPF_CHANGE },  // OP_FILTER
    { 'g', '~', OPF_CHANGE },              // OP_TILDE
    { '=', NUL, OPF_LINES | OPF_CHANGE },  // OP_INDENT
    { 'g', 'q', OPF_LINES | OPF_CHANGE },  // OP_FORMAT
    { ':', NUL, OPF_LINES },               // OP_COLON
    { 'g', 'U', OPF_CHANGE },              // OP_UPPER
    { 'g', 'u', OPF_CHANGE },              // OP_LOWER
    { 'J', NUL, OPF_LINES | OPF_CHANGE },  // DO_JOIN
    { 'g', 'J', OPF_LINES | OPF_CHANGE },  // DO_JOIN_NS
    { 'g', '?', OPF_CHANGE },              // OP_ROT13
    { 'r', NUL, OPF_CHANGE },              // OP_REPLACE
    { 'I', NUL, OPF_CHANGE },              // OP_INSERT
    { 'A', NUL, OPF_CHANGE },              // OP_APPEND
    { 'z', 'f', 0         },               // OP_FOLD
    { 'z', 'o', OPF_LINES },               // OP_FOLDOPEN
    { 'z', 'O', OPF_LINES },               // OP_FOLDOPENREC
    { 'z', 'c', OPF_LINES },               // OP_FOLDCLOSE
    { 'z', 'C', OPF_LINES },               // OP_FOLDCLOSEREC
    { 'z', 'd', OPF_LINES },               // OP_FOLDDEL
    { 'z', 'D', OPF_LINES },               // OP_FOLDDELREC
    { 'g', 'w', OPF_LINES | OPF_CHANGE },  // OP_FORMAT2
    { 'g', '@', OPF_CHANGE },              // OP_FUNCTION
    { Ctrl_A, NUL, OPF_CHANGE },           // OP_NR_ADD
    { Ctrl_X, NUL, OPF_CHANGE },           // OP_NR_SUB
  };
  
  /*
   * Translate a command name into an operator type.
   * Must only be called with a valid operator name!
   */
  int get_op_type(int char1, int char2)
  {
    int i;
  
    if (char1 == 'r') {
      // ignore second character
      return OP_REPLACE;
    }
    if (char1 == '~') {
      // when tilde is an operator
      return OP_TILDE;
    }
    if (char1 == 'g' && char2 == Ctrl_A) {
      // add
      return OP_NR_ADD;
    }
    if (char1 == 'g' && char2 == Ctrl_X) {
      // subtract
      return OP_NR_SUB;
    }
    for (i = 0;; i++) {
      if (opchars[i][0] == char1 && opchars[i][1] == char2) {
        break;
      }
      if (i == (int)(ARRAY_SIZE(opchars) - 1)) {
        internal_error("get_op_type()");
        break;
      }
    }
    return i;
  }
  
  /*
   * Return TRUE if operator "op" always works on whole lines.
   */
  int op_on_lines(int op)
  {
    return opchars[op][2] & OPF_LINES;
  }
  
  // Return TRUE if operator "op" changes text.
  int op_is_change(int op)
  {
      return opchars[op][2] & OPF_CHANGE;
  }
  
  /*
   * Get first operator command character.
   * Returns 'g' or 'z' if there is another command character.
   */
  int get_op_char(int optype)
  {
    return opchars[optype][0];
  }
  
  /*
   * Get second operator command character.
   */
  int get_extra_op_char(int optype)
  {
    return opchars[optype][1];
  }
  
  /*
   * op_shift - handle a shift operation
   */
  void op_shift(oparg_T *oap, int curs_top, int amount)
  {
    long i;
    int first_char;
    char_u          *s;
    int block_col = 0;
  
    if (u_save((linenr_T)(oap->start.lnum - 1),
            (linenr_T)(oap->end.lnum + 1)) == FAIL)
      return;
  
    if (oap->motion_type == kMTBlockWise) {
      block_col = curwin->w_cursor.col;
    }
  
    for (i = oap->line_count - 1; i >= 0; i--) {
      first_char = *get_cursor_line_ptr();
      if (first_char == NUL) {  // empty line
        curwin->w_cursor.col = 0;
      } else if (oap->motion_type == kMTBlockWise) {
        shift_block(oap, amount);
      } else if (first_char != '#' || !preprocs_left()) {
        // Move the line right if it doesn't start with '#', 'smartindent'
        // isn't set or 'cindent' isn't set or '#' isn't in 'cino'.
        shift_line(oap->op_type == OP_LSHIFT, p_sr, amount, false);
      }
      ++curwin->w_cursor.lnum;
    }
  
    if (oap->motion_type == kMTBlockWise) {
      curwin->w_cursor.lnum = oap->start.lnum;
      curwin->w_cursor.col = block_col;
    } else if (curs_top) { /* put cursor on first line, for ">>" */
      curwin->w_cursor.lnum = oap->start.lnum;
      beginline(BL_SOL | BL_FIX);       /* shift_line() may have set cursor.col */
    } else
      --curwin->w_cursor.lnum;            /* put cursor on last line, for ":>" */
  
    // The cursor line is not in a closed fold
    foldOpenCursor();
  
    if (oap->line_count > p_report) {
      if (oap->op_type == OP_RSHIFT)
        s = (char_u *)">";
      else
        s = (char_u *)"<";
      if (oap->line_count == 1) {
        if (amount == 1)
          sprintf((char *)IObuff, _("1 line %sed 1 time"), s);
        else
          sprintf((char *)IObuff, _("1 line %sed %d times"), s, amount);
      } else {
        if (amount == 1)
          sprintf((char *)IObuff, _("%" PRId64 " lines %sed 1 time"),
              (int64_t)oap->line_count, s);
        else
          sprintf((char *)IObuff, _("%" PRId64 " lines %sed %d times"),
              (int64_t)oap->line_count, s, amount);
      }
      msg_attr_keep(IObuff, 0, true, false);
    }
  
    /*
     * Set "'[" and "']" marks.
     */
    curbuf->b_op_start = oap->start;
    curbuf->b_op_end.lnum = oap->end.lnum;
    curbuf->b_op_end.col = (colnr_T)STRLEN(ml_get(oap->end.lnum));
    if (curbuf->b_op_end.col > 0) {
      curbuf->b_op_end.col--;
    }
  
    changed_lines(oap->start.lnum, 0, oap->end.lnum + 1, 0L, true);
  }
  
  // Shift the current line one shiftwidth left (if left != 0) or right
  // leaves cursor on first blank in the line.
  void shift_line(
      int left,
      int round,
      int amount,
      int call_changed_bytes  // call changed_bytes()
  )
  {
    int count;
    int i, j;
    int p_sw = get_sw_value(curbuf);
  
    count = get_indent();  // get current indent
  
    if (round) {  // round off indent
      i = count / p_sw;  // number of p_sw rounded down
      j = count % p_sw;  // extra spaces
      if (j && left) {  // first remove extra spaces
        amount--;
      }
      if (left) {
        i -= amount;
        if (i < 0)
          i = 0;
      } else
        i += amount;
      count = i * p_sw;
    } else {  // original vi indent
      if (left) {
        count -= p_sw * amount;
        if (count < 0)
          count = 0;
      } else
        count += p_sw * amount;
    }
  
    // Set new indent
    if (State & VREPLACE_FLAG) {
      change_indent(INDENT_SET, count, false, NUL, call_changed_bytes);
    } else {
      (void)set_indent(count, call_changed_bytes ? SIN_CHANGED : 0);
    }
  }
  
  /*
   * Shift one line of the current block one shiftwidth right or left.
   * Leaves cursor on first character in block.
   */
  static void shift_block(oparg_T *oap, int amount)
  {
    const bool left = (oap->op_type == OP_LSHIFT);
    const int oldstate = State;
    char_u *newp;
    const int oldcol = curwin->w_cursor.col;
    const int p_sw = get_sw_value(curbuf);
    const int p_ts = (int)curbuf->b_p_ts;
    struct block_def bd;
    int incr;
    int i = 0, j = 0;
    const int old_p_ri = p_ri;
  
    p_ri = 0;                     /* don't want revins in indent */
  
    State = INSERT;               // don't want REPLACE for State
    block_prep(oap, &bd, curwin->w_cursor.lnum, true);
    if (bd.is_short) {
      return;
    }
  
    // total is number of screen columns to be inserted/removed
    int total = (int)((unsigned)amount * (unsigned)p_sw);
    if ((total / p_sw) != amount) {
      return;   // multiplication overflow
    }
  
    char_u *const oldp = get_cursor_line_ptr();
  
    int startcol, oldlen, newlen;
  
    if (!left) {
      /*
       *  1. Get start vcol
       *  2. Total ws vcols
       *  3. Divvy into TABs & spp
       *  4. Construct new string
       */
      total += bd.pre_whitesp;    // all virtual WS up to & incl a split TAB
      colnr_T ws_vcol = bd.start_vcol - bd.pre_whitesp;
      char_u * old_textstart = bd.textstart;
      if (bd.startspaces) {
        if (utfc_ptr2len(bd.textstart) == 1) {
          bd.textstart++;
        } else {
          ws_vcol = 0;
          bd.startspaces = 0;
        }
      }
      for (; ascii_iswhite(*bd.textstart); ) {
        // TODO: is passing bd.textstart for start of the line OK?
        incr = lbr_chartabsize_adv(bd.textstart, &bd.textstart, (colnr_T)(bd.start_vcol));
        total += incr;
        bd.start_vcol += incr;
      }
      /* OK, now total=all the VWS reqd, and textstart points at the 1st
       * non-ws char in the block. */
      if (!curbuf->b_p_et)
        i = ((ws_vcol % p_ts) + total) / p_ts;       /* number of tabs */
      if (i)
        j = ((ws_vcol % p_ts) + total) % p_ts;       /* number of spp */
      else
        j = total;
  
      // if we're splitting a TAB, allow for it
      int col_pre = bd.pre_whitesp_c - (bd.startspaces != 0);
      bd.textcol -= col_pre;
      const int len = (int)STRLEN(bd.textstart) + 1;
      int col = bd.textcol + i +j + len;
      assert(col >= 0);
      newp = (char_u *)xmalloc((size_t)col);
      memset(newp, NUL, (size_t)col);
      memmove(newp, oldp, (size_t)bd.textcol);
      startcol = bd.textcol;
      oldlen = (int)(bd.textstart-old_textstart) + col_pre;
      newlen = i+j;
      memset(newp + bd.textcol, TAB, (size_t)i);
      memset(newp + bd.textcol + i, ' ', (size_t)j);
      /* the end */
      memmove(newp + bd.textcol + i + j, bd.textstart, (size_t)len);
    } else {  // left
      colnr_T destination_col;      // column to which text in block will
                                    // be shifted
      char_u *verbatim_copy_end;    // end of the part of the line which is
                                    // copied verbatim
      colnr_T verbatim_copy_width;  // the (displayed) width of this part
                                    // of line
      size_t fill;                  // nr of spaces that replace a TAB
      size_t new_line_len;          // the length of the line after the
                                    // block shift
      char_u      *non_white = bd.textstart;
  
      /*
       * Firstly, let's find the first non-whitespace character that is
       * displayed after the block's start column and the character's column
       * number. Also, let's calculate the width of all the whitespace
       * characters that are displayed in the block and precede the searched
       * non-whitespace character.
       */
  
      /* If "bd.startspaces" is set, "bd.textstart" points to the character,
       * the part of which is displayed at the block's beginning. Let's start
       * searching from the next character. */
      if (bd.startspaces) {
        MB_PTR_ADV(non_white);
      }
  
      // The character's column is in "bd.start_vcol".
      colnr_T non_white_col = bd.start_vcol;
  
      while (ascii_iswhite(*non_white)) {
        incr = lbr_chartabsize_adv(bd.textstart, &non_white, non_white_col);
        non_white_col += incr;
      }
  
  
      const colnr_T block_space_width = non_white_col - oap->start_vcol;
      // We will shift by "total" or "block_space_width", whichever is less.
      const colnr_T shift_amount = block_space_width < total
          ? block_space_width
          : total;
      // The column to which we will shift the text.
      destination_col = non_white_col - shift_amount;
  
      /* Now let's find out how much of the beginning of the line we can
       * reuse without modification.  */
      verbatim_copy_end = bd.textstart;
      verbatim_copy_width = bd.start_vcol;
  
      /* If "bd.startspaces" is set, "bd.textstart" points to the character
       * preceding the block. We have to subtract its width to obtain its
       * column number.  */
      if (bd.startspaces)
        verbatim_copy_width -= bd.start_char_vcols;
      while (verbatim_copy_width < destination_col) {
        char_u *line = verbatim_copy_end;
  
        // TODO: is passing verbatim_copy_end for start of the line OK?
        incr = lbr_chartabsize(line, verbatim_copy_end, verbatim_copy_width);
        if (verbatim_copy_width + incr > destination_col)
          break;
        verbatim_copy_width += incr;
        MB_PTR_ADV(verbatim_copy_end);
      }
  
      /* If "destination_col" is different from the width of the initial
      * part of the line that will be copied, it means we encountered a tab
      * character, which we will have to partly replace with spaces.  */
      assert(destination_col - verbatim_copy_width >= 0);
      fill = (size_t)(destination_col - verbatim_copy_width);
  
      assert(verbatim_copy_end - oldp >= 0);
      const size_t verbatim_diff = (size_t)(verbatim_copy_end - oldp);
      // The replacement line will consist of:
      // - the beginning of the original line up to "verbatim_copy_end",
      // - "fill" number of spaces,
      // - the rest of the line, pointed to by non_white.
      new_line_len = verbatim_diff + fill + STRLEN(non_white) + 1;
  
      newp = (char_u *)xmalloc(new_line_len);
      startcol = (int)verbatim_diff;
      oldlen = bd.textcol + (int)(non_white - bd.textstart) - (int)verbatim_diff;
      newlen = (int)fill;
      memmove(newp, oldp, verbatim_diff);
      memset(newp + verbatim_diff, ' ', fill);
      STRMOVE(newp + verbatim_diff + fill, non_white);
    }
    // replace the line
    ml_replace(curwin->w_cursor.lnum, newp, false);
    changed_bytes(curwin->w_cursor.lnum, (colnr_T)bd.textcol);
    extmark_splice_cols(curbuf, (int)curwin->w_cursor.lnum-1, startcol,
                        oldlen, newlen,
                        kExtmarkUndo);
    State = oldstate;
    curwin->w_cursor.col = oldcol;
    p_ri = old_p_ri;
  }
  
  /*
   * Insert string "s" (b_insert ? before : after) block :AKelly
   * Caller must prepare for undo.
   */
  static void block_insert(oparg_T *oap, char_u *s, int b_insert, struct block_def *bdp)
  {
    int p_ts;
    int count = 0;                // extra spaces to replace a cut TAB
    int spaces = 0;               // non-zero if cutting a TAB
    colnr_T offset;               // pointer along new line
    size_t s_len = STRLEN(s);
    char_u      *newp, *oldp;     // new, old lines
    linenr_T lnum;                // loop var
    int oldstate = State;
    State = INSERT;               // don't want REPLACE for State
  
    for (lnum = oap->start.lnum + 1; lnum <= oap->end.lnum; lnum++) {
      block_prep(oap, bdp, lnum, true);
      if (bdp->is_short && b_insert) {
        continue;  // OP_INSERT, line ends before block start
      }
  
      oldp = ml_get(lnum);
  
      if (b_insert) {
        p_ts = bdp->start_char_vcols;
        spaces = bdp->startspaces;
        if (spaces != 0)
          count = p_ts - 1;         /* we're cutting a TAB */
        offset = bdp->textcol;
      } else { /* append */
        p_ts = bdp->end_char_vcols;
        if (!bdp->is_short) {     /* spaces = padding after block */
          spaces = (bdp->endspaces ? p_ts - bdp->endspaces : 0);
          if (spaces != 0)
            count = p_ts - 1;           /* we're cutting a TAB */
          offset = bdp->textcol + bdp->textlen - (spaces != 0);
        } else { /* spaces = padding to block edge */
                   /* if $ used, just append to EOL (ie spaces==0) */
          if (!bdp->is_MAX)
            spaces = (oap->end_vcol - bdp->end_vcol) + 1;
          count = spaces;
          offset = bdp->textcol + bdp->textlen;
        }
      }
  
      if (spaces > 0) {
        int off;
  
        // Avoid starting halfway through a multi-byte character.
        if (b_insert) {
          off = utf_head_off(oldp, oldp + offset + spaces);
        } else {
          off = (*mb_off_next)(oldp, oldp + offset);
          offset += off;
        }
        spaces -= off;
        count -= off;
      }
  
      assert(count >= 0);
      newp = (char_u *)xmalloc(STRLEN(oldp) + s_len + (size_t)count + 1);
  
      // copy up to shifted part
      memmove(newp, oldp, (size_t)offset);
      oldp += offset;
      int startcol = offset;
  
      // insert pre-padding
      memset(newp + offset, ' ', (size_t)spaces);
  
      // copy the new text
      memmove(newp + offset + spaces, s, s_len);
      offset += (int)s_len;
  
      int skipped = 0;
      if (spaces && !bdp->is_short) {
        // insert post-padding
        memset(newp + offset + spaces, ' ', (size_t)(p_ts - spaces));
        // We're splitting a TAB, don't copy it.
        oldp++;
        // We allowed for that TAB, remember this now
        count++;
        skipped = 1;
      }
  
      if (spaces > 0)
        offset += count;
      STRMOVE(newp + offset, oldp);
  
      ml_replace(lnum, newp, false);
      extmark_splice_cols(curbuf, (int)lnum-1, startcol,
                          skipped, offset-startcol, kExtmarkUndo);
  
      if (lnum == oap->end.lnum) {
        /* Set "']" mark to the end of the block instead of the end of
         * the insert in the first line.  */
        curbuf->b_op_end.lnum = oap->end.lnum;
        curbuf->b_op_end.col = offset;
      }
    }   /* for all lnum */
  
    changed_lines(oap->start.lnum + 1, 0, oap->end.lnum + 1, 0L, true);
  
    State = oldstate;
  }
  
  /*
   * op_reindent - handle reindenting a block of lines.
   */
  void op_reindent(oparg_T *oap, Indenter how)
  {
    long i;
    char_u      *l;
    int amount;
    linenr_T first_changed = 0;
    linenr_T last_changed = 0;
    linenr_T start_lnum = curwin->w_cursor.lnum;
  
    /* Don't even try when 'modifiable' is off. */
    if (!MODIFIABLE(curbuf)) {
      EMSG(_(e_modifiable));
      return;
    }
  
    for (i = oap->line_count - 1; i >= 0 && !got_int; i--) {
      /* it's a slow thing to do, so give feedback so there's no worry that
       * the computer's just hung. */
  
      if (i > 1
          && (i % 50 == 0 || i == oap->line_count - 1)
          && oap->line_count > p_report)
        smsg(_("%" PRId64 " lines to indent... "), (int64_t)i);
  
      /*
       * Be vi-compatible: For lisp indenting the first line is not
       * indented, unless there is only one line.
       */
      if (i != oap->line_count - 1 || oap->line_count == 1
          || how != get_lisp_indent) {
        l = skipwhite(get_cursor_line_ptr());
        if (*l == NUL)                        /* empty or blank line */
          amount = 0;
        else
          amount = how();                     /* get the indent for this line */
  
        if (amount >= 0 && set_indent(amount, SIN_UNDO)) {
          // did change the indent, call changed_lines() later
          if (first_changed == 0) {
            first_changed = curwin->w_cursor.lnum;
          }
          last_changed = curwin->w_cursor.lnum;
        }
      }
      ++curwin->w_cursor.lnum;
      curwin->w_cursor.col = 0;      /* make sure it's valid */
    }
  
    /* put cursor on first non-blank of indented line */
    curwin->w_cursor.lnum = start_lnum;
    beginline(BL_SOL | BL_FIX);
  
    /* Mark changed lines so that they will be redrawn.  When Visual
     * highlighting was present, need to continue until the last line.  When
     * there is no change still need to remove the Visual highlighting. */
    if (last_changed != 0) {
      changed_lines(first_changed, 0,
                    oap->is_VIsual ? start_lnum + oap->line_count :
                    last_changed + 1, 0L, true);
    } else if (oap->is_VIsual) {
      redraw_curbuf_later(INVERTED);
    }
  
    if (oap->line_count > p_report) {
      i = oap->line_count - (i + 1);
      if (i == 1)
        MSG(_("1 line indented "));
      else
        smsg(_("%" PRId64 " lines indented "), (int64_t)i);
    }
    /* set '[ and '] marks */
    curbuf->b_op_start = oap->start;
    curbuf->b_op_end = oap->end;
  }
  
  /*
   * Keep the last expression line here, for repeating.
   */
  static char_u   *expr_line = NULL;
  
  /*
   * Get an expression for the "\"=expr1" or "CTRL-R =expr1"
   * Returns '=' when OK, NUL otherwise.
   */
  int get_expr_register(void)
  {
    char_u      *new_line;
  
    new_line = getcmdline('=', 0L, 0, true);
    if (new_line == NULL) {
      return NUL;
    }
    if (*new_line == NUL) {  // use previous line
      xfree(new_line);
    } else {
      set_expr_line(new_line);
    }
    return '=';
  }
  
  /*
   * Set the expression for the '=' register.
   * Argument must be an allocated string.
   */
  void set_expr_line(char_u *new_line)
  {
    xfree(expr_line);
    expr_line = new_line;
  }
  
  /*
   * Get the result of the '=' register expression.
   * Returns a pointer to allocated memory, or NULL for failure.
   */
  char_u *get_expr_line(void)
  {
    char_u      *expr_copy;
    char_u      *rv;
    static int nested = 0;
  
    if (expr_line == NULL)
      return NULL;
  
    /* Make a copy of the expression, because evaluating it may cause it to be
     * changed. */
    expr_copy = vim_strsave(expr_line);
  
    /* When we are invoked recursively limit the evaluation to 10 levels.
     * Then return the string as-is. */
    if (nested >= 10)
      return expr_copy;
  
    ++nested;
    rv = eval_to_string(expr_copy, NULL, TRUE);
    --nested;
    xfree(expr_copy);
    return rv;
  }
  
  /*
   * Get the '=' register expression itself, without evaluating it.
   */
  char_u *get_expr_line_src(void)
  {
    if (expr_line == NULL)
      return NULL;
    return vim_strsave(expr_line);
  }
  
  /// Returns whether `regname` is a valid name of a yank register.
  /// Note: There is no check for 0 (default register), caller should do this.
  /// The black hole register '_' is regarded as valid.
  ///
  /// @param regname name of register
  /// @param writing allow only writable registers
  bool valid_yank_reg(int regname, bool writing)
  {
    if ((regname > 0 && ASCII_ISALNUM(regname))
        || (!writing && vim_strchr((char_u *) "/.%:=" , regname) != NULL)
        || regname == '#'
        || regname == '"'
        || regname == '-'
        || regname == '_'
        || regname == '*'
        || regname == '+') {
      return true;
    }
    return false;
  }
  
  typedef enum {
    YREG_PASTE,
    YREG_YANK,
    YREG_PUT,
  } yreg_mode_t;
  
  /// Return yankreg_T to use, according to the value of `regname`.
  /// Cannot handle the '_' (black hole) register.
  /// Must only be called with a valid register name!
  ///
  /// @param regname The name of the register used or 0 for the unnamed register
  /// @param mode One of the following three flags:
  ///
  /// `YREG_PASTE`:
  /// Prepare for pasting the register `regname`. With no regname specified,
  /// read from last written register, or from unnamed clipboard (depending on the
  /// `clipboard=unnamed` option). Queries the clipboard provider if necessary.
  ///
  /// `YREG_YANK`:
  /// Preparare for yanking into `regname`. With no regname specified,
  /// yank into `"0` register. Update `y_previous` for next unnamed paste.
  ///
  /// `YREG_PUT`:
  /// Obtain the location that would be read when pasting `regname`.
  yankreg_T *get_yank_register(int regname, int mode)
  {
    yankreg_T *reg;
  
    if (mode == YREG_PASTE && get_clipboard(regname, &reg, false)) {
      // reg is set to clipboard contents.
      return reg;
    } else if (mode != YREG_YANK
        && (regname == 0 || regname == '"' || regname == '*' || regname == '+')
        && y_previous != NULL) {
      // in case clipboard not available, paste from previous used register
      return y_previous;
    }
  
    int i = op_reg_index(regname);
    // when not 0-9, a-z, A-Z or '-'/'+'/'*': use register 0
    if (i == -1) {
      i = 0;
    }
    reg = &y_regs[i];
  
    if (mode == YREG_YANK) {
      // remember the written register for unnamed paste
      y_previous = reg;
    }
    return reg;
  }
  
  static bool is_append_register(int regname)
  {
    return ASCII_ISUPPER(regname);
  }
  
  /// @see get_yank_register
  /// @returns true when register should be inserted literally
  /// (selection or clipboard)
  static inline bool is_literal_register(int regname)
    FUNC_ATTR_CONST
  {
    return regname == '*' || regname == '+';
  }
  
  /// Returns a copy of contents in register `name`
  /// for use in do_put. Should be freed by caller.
  yankreg_T *copy_register(int name)
    FUNC_ATTR_NONNULL_RET
  {
    yankreg_T *reg = get_yank_register(name, YREG_PASTE);
  
    yankreg_T *copy = xmalloc(sizeof(yankreg_T));
    *copy = *reg;
    if (copy->y_size == 0) {
      copy->y_array = NULL;
    } else {
      copy->y_array = xcalloc(copy->y_size, sizeof(char_u *));
      for (size_t i = 0; i < copy->y_size; i++) {
        copy->y_array[i] = vim_strsave(reg->y_array[i]);
      }
    }
    return copy;
  }
  
  /// check if the current yank register has kMTLineWise register type
  bool yank_register_mline(int regname)
  {
    if (regname != 0 && !valid_yank_reg(regname, false)) {
      return false;
    }
    if (regname == '_') {  // black hole is always empty
      return false;
    }
    yankreg_T *reg = get_yank_register(regname, YREG_PASTE);
    return reg->y_type == kMTLineWise;
  }
  
  /*
   * Start or stop recording into a yank register.
   *
   * Return FAIL for failure, OK otherwise.
   */
  int do_record(int c)
  {
    char_u          *p;
    static int regname;
    yankreg_T  *old_y_previous;
    int retval;
  
    if (reg_recording == 0) {
      // start recording
      // registers 0-9, a-z and " are allowed
      if (c < 0 || (!ASCII_ISALNUM(c) && c != '"')) {
        retval = FAIL;
      } else {
        reg_recording = c;
        showmode();
        regname = c;
        retval = OK;
      }
    } else {                        /* stop recording */
      /*
       * Get the recorded key hits.  K_SPECIAL and CSI will be escaped, this
       * needs to be removed again to put it in a register.  exec_reg then
       * adds the escaping back later.
       */
      reg_recording = 0;
      if (ui_has(kUIMessages)) {
        showmode();
      } else {
        MSG("");
      }
      p = get_recorded();
      if (p == NULL)
        retval = FAIL;
      else {
        /* Remove escaping for CSI and K_SPECIAL in multi-byte chars. */
        vim_unescape_csi(p);
  
        /*
         * We don't want to change the default register here, so save and
         * restore the current register name.
         */
        old_y_previous = y_previous;
  
        retval = stuff_yank(regname, p);
  
        y_previous = old_y_previous;
      }
    }
    return retval;
  }
  
  static void set_yreg_additional_data(yankreg_T *reg, dict_T *additional_data)
    FUNC_ATTR_NONNULL_ARG(1)
  {
    if (reg->additional_data == additional_data) {
      return;
    }
    tv_dict_unref(reg->additional_data);
    reg->additional_data = additional_data;
  }
  
  /*
   * Stuff string "p" into yank register "regname" as a single line (append if
   * uppercase). "p" must have been alloced.
   *
   * return FAIL for failure, OK otherwise
   */
  static int stuff_yank(int regname, char_u *p)
  {
    /* check for read-only register */
    if (regname != 0 && !valid_yank_reg(regname, true)) {
      xfree(p);
      return FAIL;
    }
    if (regname == '_') {             /* black hole: don't do anything */
      xfree(p);
      return OK;
    }
    yankreg_T *reg = get_yank_register(regname, YREG_YANK);
    if (is_append_register(regname) && reg->y_array != NULL) {
      char_u **pp = &(reg->y_array[reg->y_size - 1]);
      char_u *lp = xmalloc(STRLEN(*pp) + STRLEN(p) + 1);
      STRCPY(lp, *pp);
      // TODO(philix): use xstpcpy() in stuff_yank()
      STRCAT(lp, p);
      xfree(p);
      xfree(*pp);
      *pp = lp;
    } else {
      free_register(reg);
      set_yreg_additional_data(reg, NULL);
      reg->y_array = (char_u **)xmalloc(sizeof(char_u *));
      reg->y_array[0] = p;
      reg->y_size = 1;
      reg->y_type = kMTCharWise;
    }
    reg->timestamp = os_time();
    return OK;
  }
  
  static int execreg_lastc = NUL;
  
  /// Execute a yank register: copy it into the stuff buffer
  ///
  /// Return FAIL for failure, OK otherwise
  int
  do_execreg(
      int regname,
      int colon,                      /* insert ':' before each line */
      int addcr,                      /* always add '\n' to end of line */
      int silent                     /* set "silent" flag in typeahead buffer */
  )
  {
    char_u *p;
    int retval = OK;
  
    if (regname == '@') {                 /* repeat previous one */
      if (execreg_lastc == NUL) {
        EMSG(_("E748: No previously used register"));
        return FAIL;
      }
      regname = execreg_lastc;
    }
    /* check for valid regname */
    if (regname == '%' || regname == '#' || !valid_yank_reg(regname, false)) {
      emsg_invreg(regname);
      return FAIL;
    }
    execreg_lastc = regname;
  
    if (regname == '_')                   /* black hole: don't stuff anything */
      return OK;
  
    if (regname == ':') {                 /* use last command line */
      if (last_cmdline == NULL) {
        EMSG(_(e_nolastcmd));
        return FAIL;
      }
      // don't keep the cmdline containing @:
      XFREE_CLEAR(new_last_cmdline);
      // Escape all control characters with a CTRL-V
      p = vim_strsave_escaped_ext(
          last_cmdline,
          (char_u *)"\001\002\003\004\005\006\007"
          "\010\011\012\013\014\015\016\017"
          "\020\021\022\023\024\025\026\027"
          "\030\031\032\033\034\035\036\037",
          Ctrl_V, false);
      // When in Visual mode "'<,'>" will be prepended to the command.
      // Remove it when it's already there.
      if (VIsual_active && STRNCMP(p, "'<,'>", 5) == 0) {
        retval = put_in_typebuf(p + 5, true, true, silent);
      } else {
        retval = put_in_typebuf(p, true, true, silent);
      }
      xfree(p);
    } else if (regname == '=') {
      p = get_expr_line();
      if (p == NULL)
        return FAIL;
      retval = put_in_typebuf(p, true, colon, silent);
      xfree(p);
    } else if (regname == '.') {        /* use last inserted text */
      p = get_last_insert_save();
      if (p == NULL) {
        EMSG(_(e_noinstext));
        return FAIL;
      }
      retval = put_in_typebuf(p, false, colon, silent);
      xfree(p);
    } else {
      yankreg_T *reg = get_yank_register(regname, YREG_PASTE);
      if (reg->y_array == NULL)
        return FAIL;
  
      // Disallow remaping for ":@r".
      int remap = colon ? REMAP_NONE : REMAP_YES;
  
      /*
       * Insert lines into typeahead buffer, from last one to first one.
       */
      put_reedit_in_typebuf(silent);
      char_u *escaped;
      for (size_t i = reg->y_size; i-- > 0;) {  // from y_size - 1 to 0 included
        // insert NL between lines and after last line if type is kMTLineWise
        if (reg->y_type == kMTLineWise || i < reg->y_size - 1 || addcr) {
          if (ins_typebuf((char_u *)"\n", remap, 0, true, silent) == FAIL) {
            return FAIL;
          }
        }
        escaped = vim_strsave_escape_csi(reg->y_array[i]);
        retval = ins_typebuf(escaped, remap, 0, TRUE, silent);
        xfree(escaped);
        if (retval == FAIL)
          return FAIL;
        if (colon && ins_typebuf((char_u *)":", remap, 0, TRUE, silent)
            == FAIL)
          return FAIL;
      }
      reg_executing = regname == 0 ? '"' : regname;  // disable the 'q' command
    }
    return retval;
  }
  
  /*
   * If "restart_edit" is not zero, put it in the typeahead buffer, so that it's
   * used only after other typeahead has been processed.
   */
  static void put_reedit_in_typebuf(int silent)
  {
    char_u buf[3];
  
    if (restart_edit != NUL) {
      if (restart_edit == 'V') {
        buf[0] = 'g';
        buf[1] = 'R';
        buf[2] = NUL;
      } else {
        buf[0] = (char_u)(restart_edit == 'I' ? 'i' : restart_edit);
        buf[1] = NUL;
      }
      if (ins_typebuf(buf, REMAP_NONE, 0, TRUE, silent) == OK)
        restart_edit = NUL;
    }
  }
  
  /*
   * Insert register contents "s" into the typeahead buffer, so that it will be
   * executed again.
   * When "esc" is TRUE it is to be taken literally: Escape CSI characters and
   * no remapping.
   */
  static int put_in_typebuf(
      char_u *s,
      bool esc,
      bool colon,                 // add ':' before the line
      int silent
  )
  {
    int retval = OK;
  
    put_reedit_in_typebuf(silent);
    if (colon)
      retval = ins_typebuf((char_u *)"\n", REMAP_NONE, 0, TRUE, silent);
    if (retval == OK) {
      char_u  *p;
  
      if (esc)
        p = vim_strsave_escape_csi(s);
      else
        p = s;
      if (p == NULL)
        retval = FAIL;
      else
        retval = ins_typebuf(p, esc ? REMAP_NONE : REMAP_YES,
            0, TRUE, silent);
      if (esc)
        xfree(p);
    }
    if (colon && retval == OK)
      retval = ins_typebuf((char_u *)":", REMAP_NONE, 0, TRUE, silent);
    return retval;
  }
  
  /*
   * Insert a yank register: copy it into the Read buffer.
   * Used by CTRL-R command and middle mouse button in insert mode.
   *
   * return FAIL for failure, OK otherwise
   */
  int insert_reg(
      int regname,
      bool literally_arg            // insert literally, not as if typed
  )
  {
    int retval = OK;
    bool allocated;
    const bool literally = literally_arg || is_literal_register(regname);
  
    /*
     * It is possible to get into an endless loop by having CTRL-R a in
     * register a and then, in insert mode, doing CTRL-R a.
     * If you hit CTRL-C, the loop will be broken here.
     */
    os_breakcheck();
    if (got_int)
      return FAIL;
  
    /* check for valid regname */
    if (regname != NUL && !valid_yank_reg(regname, false))
      return FAIL;
  
    char_u *arg;
    if (regname == '.') {  // Insert last inserted text.
      retval = stuff_inserted(NUL, 1L, true);
    } else if (get_spec_reg(regname, &arg, &allocated, true)) {
      if (arg == NULL) {
        return FAIL;
      }
      stuffescaped((const char *)arg, literally);
      if (allocated) {
        xfree(arg);
      }
    } else {  // Name or number register.
      yankreg_T *reg = get_yank_register(regname, YREG_PASTE);
      if (reg->y_array == NULL) {
        retval = FAIL;
      } else {
        for (size_t i = 0; i < reg->y_size; i++) {
          stuffescaped((const char *)reg->y_array[i], literally);
          // Insert a newline between lines and after last line if
          // y_type is kMTLineWise.
          if (reg->y_type == kMTLineWise || i < reg->y_size - 1) {
            stuffcharReadbuff('\n');
          }
        }
      }
    }
  
    return retval;
  }
  
  /*
   * Stuff a string into the typeahead buffer, such that edit() will insert it
   * literally ("literally" TRUE) or interpret is as typed characters.
   */
  static void stuffescaped(const char *arg, int literally)
  {
    while (*arg != NUL) {
      // Stuff a sequence of normal ASCII characters, that's fast.  Also
      // stuff K_SPECIAL to get the effect of a special key when "literally"
      // is TRUE.
      const char *const start = arg;
      while ((*arg >= ' ' && *arg < DEL) || ((uint8_t)(*arg) == K_SPECIAL
                                             && !literally)) {
        arg++;
      }
      if (arg > start) {
        stuffReadbuffLen(start, (long)(arg - start));
      }
  
      /* stuff a single special character */
      if (*arg != NUL) {
        const int c = mb_cptr2char_adv((const char_u **)&arg);
        if (literally && ((c < ' ' && c != TAB) || c == DEL)) {
          stuffcharReadbuff(Ctrl_V);
        }
        stuffcharReadbuff(c);
      }
    }
  }
  
  // If "regname" is a special register, return true and store a pointer to its
  // value in "argp".
  bool get_spec_reg(
      int regname,
      char_u **argp,
      bool *allocated,        // return: true when value was allocated
      bool errmsg             // give error message when failing
  )
  {
    size_t cnt;
  
    *argp = NULL;
    *allocated = false;
    switch (regname) {
    case '%':                     /* file name */
      if (errmsg)
        check_fname();            /* will give emsg if not set */
      *argp = curbuf->b_fname;
      return true;
  
    case '#':                       // alternate file name
      *argp = getaltfname(errmsg);  // may give emsg if not set
      return true;
  
    case '=':                     /* result of expression */
      *argp = get_expr_line();
      *allocated = true;
      return true;
  
    case ':':                     /* last command line */
      if (last_cmdline == NULL && errmsg)
        EMSG(_(e_nolastcmd));
      *argp = last_cmdline;
      return true;
  
    case '/':                     /* last search-pattern */
      if (last_search_pat() == NULL && errmsg)
        EMSG(_(e_noprevre));
      *argp = last_search_pat();
      return true;
  
    case '.':                     /* last inserted text */
      *argp = get_last_insert_save();
      *allocated = true;
      if (*argp == NULL && errmsg) {
        EMSG(_(e_noinstext));
      }
      return true;
  
    case Ctrl_F:                  // Filename under cursor
    case Ctrl_P:                  // Path under cursor, expand via "path"
      if (!errmsg) {
        return false;
      }
      *argp = file_name_at_cursor(
          FNAME_MESS | FNAME_HYP | (regname == Ctrl_P ? FNAME_EXP : 0),
          1L, NULL);
      *allocated = true;
      return true;
  
    case Ctrl_W:                  // word under cursor
    case Ctrl_A:                  // WORD (mnemonic All) under cursor
      if (!errmsg) {
        return false;
      }
      cnt = find_ident_under_cursor(argp, (regname == Ctrl_W
                                           ? (FIND_IDENT|FIND_STRING)
                                           : FIND_STRING));
      *argp = cnt ? vim_strnsave(*argp, cnt) : NULL;
      *allocated = true;
      return true;
  
    case Ctrl_L:                  // Line under cursor
      if (!errmsg) {
        return false;
      }
  
      *argp = ml_get_buf(curwin->w_buffer, curwin->w_cursor.lnum, false);
      return true;
  
    case '_':                     /* black hole: always empty */
      *argp = (char_u *)"";
      return true;
    }
  
    return false;
  }
  
  /// Paste a yank register into the command line.
  /// Only for non-special registers.
  /// Used by CTRL-R in command-line mode.
  /// insert_reg() can't be used here, because special characters from the
  /// register contents will be interpreted as commands.
  ///
  /// @param regname   Register name.
  /// @param literally_arg Insert text literally instead of "as typed".
  /// @param remcr     When true, don't add CR characters.
  ///
  /// @returns FAIL for failure, OK otherwise
  bool cmdline_paste_reg(int regname, bool literally_arg, bool remcr)
  {
    const bool literally = literally_arg || is_literal_register(regname);
  
    yankreg_T *reg = get_yank_register(regname, YREG_PASTE);
    if (reg->y_array == NULL)
      return FAIL;
  
    for (size_t i = 0; i < reg->y_size; i++) {
      cmdline_paste_str(reg->y_array[i], literally);
  
      // Insert ^M between lines, unless `remcr` is true.
      if (i < reg->y_size - 1 && !remcr) {
        cmdline_paste_str((char_u *)"\r", literally);
      }
  
      /* Check for CTRL-C, in case someone tries to paste a few thousand
       * lines and gets bored. */
      os_breakcheck();
      if (got_int)
        return FAIL;
    }
    return OK;
  }
  
  // Shift the delete registers: "9 is cleared, "8 becomes "9, etc.
  static void shift_delete_registers(bool y_append)
  {
    free_register(&y_regs[9]);  // free register "9
    for (int n = 9; n > 1; n--) {
      y_regs[n] = y_regs[n - 1];
    }
    if (!y_append) {
      y_previous = &y_regs[1];
    }
    y_regs[1].y_array = NULL;  // set register "1 to empty
  }
  
  /*
   * Handle a delete operation.
   *
   * Return FAIL if undo failed, OK otherwise.
   */
  int op_delete(oparg_T *oap)
  {
    int n;
    linenr_T lnum;
    char_u              *ptr;
    char_u              *newp, *oldp;
    struct block_def bd = { 0 };
    linenr_T old_lcount = curbuf->b_ml.ml_line_count;
  
    if (curbuf->b_ml.ml_flags & ML_EMPTY) {  // nothing to do
      return OK;
    }
  
    // Nothing to delete, return here. Do prepare undo, for op_change().
    if (oap->empty) {
      return u_save_cursor();
    }
  
    if (!MODIFIABLE(curbuf)) {
      EMSG(_(e_modifiable));
      return FAIL;
    }
  
    mb_adjust_opend(oap);
  
    /*
     * Imitate the strange Vi behaviour: If the delete spans more than one
     * line and motion_type == kMTCharWise and the result is a blank line, make the
     * delete linewise.  Don't do this for the change command or Visual mode.
     */
    if (oap->motion_type == kMTCharWise
        && !oap->is_VIsual
        && oap->line_count > 1
        && oap->motion_force == NUL
        && oap->op_type == OP_DELETE) {
      ptr = ml_get(oap->end.lnum) + oap->end.col;
      if (*ptr != NUL)
        ptr += oap->inclusive;
      ptr = skipwhite(ptr);
      if (*ptr == NUL && inindent(0)) {
        oap->motion_type = kMTLineWise;
      }
    }
  
    /*
     * Check for trying to delete (e.g. "D") in an empty line.
     * Note: For the change operator it is ok.
     */
    if (oap->motion_type != kMTLineWise
        && oap->line_count == 1
        && oap->op_type == OP_DELETE
        && *ml_get(oap->start.lnum) == NUL) {
      // It's an error to operate on an empty region, when 'E' included in
      // 'cpoptions' (Vi compatible).
      if (virtual_op) {
        // Virtual editing: Nothing gets deleted, but we set the '[ and ']
        // marks as if it happened.
        goto setmarks;
      }
      if (vim_strchr(p_cpo, CPO_EMPTYREGION) != NULL) {
        beep_flush();
      }
      return OK;
    }
  
    /*
     * Do a yank of whatever we're about to delete.
     * If a yank register was specified, put the deleted text into that
     * register.  For the black hole register '_' don't yank anything.
     */
    if (oap->regname != '_') {
      yankreg_T *reg = NULL;
      int did_yank = false;
      if (oap->regname != 0) {
        // yank without message
        did_yank = op_yank(oap, false, true);
        if (!did_yank) {
          // op_yank failed, don't do anything
          return OK;
        }
      }
  
      /*
       * Put deleted text into register 1 and shift number registers if the
       * delete contains a line break, or when a regname has been specified.
       */
      if (oap->regname != 0 || oap->motion_type == kMTLineWise
          || oap->line_count > 1 || oap->use_reg_one) {
        shift_delete_registers(is_append_register(oap->regname));
        reg = &y_regs[1];
        op_yank_reg(oap, false, reg, false);
        did_yank = true;
      }
  
      /* Yank into small delete register when no named register specified
       * and the delete is within one line. */
      if (oap->regname == 0 && oap->motion_type != kMTLineWise
          && oap->line_count == 1) {
        reg = get_yank_register('-', YREG_YANK);
        op_yank_reg(oap, false, reg, false);
        did_yank = true;
      }
  
      if (did_yank || oap->regname == 0) {
        if (reg == NULL) {
          abort();
        }
        set_clipboard(oap->regname, reg);
        do_autocmd_textyankpost(oap, reg);
      }
  
    }
  
    /*
     * block mode delete
     */
    if (oap->motion_type == kMTBlockWise) {
      if (u_save((linenr_T)(oap->start.lnum - 1),
                 (linenr_T)(oap->end.lnum + 1)) == FAIL) {
        return FAIL;
      }
  
      for (lnum = curwin->w_cursor.lnum; lnum <= oap->end.lnum; lnum++) {
        block_prep(oap, &bd, lnum, true);
        if (bd.textlen == 0) {            // nothing to delete
          continue;
        }
  
        /* Adjust cursor position for tab replaced by spaces and 'lbr'. */
        if (lnum == curwin->w_cursor.lnum) {
          curwin->w_cursor.col = bd.textcol + bd.startspaces;
          curwin->w_cursor.coladd = 0;
        }
  
        // n == number of chars deleted
        // If we delete a TAB, it may be replaced by several characters.
        // Thus the number of characters may increase!
        n = bd.textlen - bd.startspaces - bd.endspaces;
        oldp = ml_get(lnum);
        newp = (char_u *)xmalloc(STRLEN(oldp) - (size_t)n + 1);
        // copy up to deleted part
        memmove(newp, oldp, (size_t)bd.textcol);
        // insert spaces
        memset(newp + bd.textcol, ' ', (size_t)bd.startspaces +
               (size_t)bd.endspaces);
        // copy the part after the deleted part
        oldp += bd.textcol + bd.textlen;
        STRMOVE(newp + bd.textcol + bd.startspaces + bd.endspaces, oldp);
        // replace the line
        ml_replace(lnum, newp, false);
  
        extmark_splice_cols(curbuf, (int)lnum-1, bd.textcol,
                            bd.textlen, bd.startspaces+bd.endspaces,
                            kExtmarkUndo);
      }
  
      check_cursor_col();
      changed_lines(curwin->w_cursor.lnum, curwin->w_cursor.col,
                    oap->end.lnum + 1, 0L, true);
      oap->line_count = 0;  // no lines deleted
    } else if (oap->motion_type == kMTLineWise) {
      if (oap->op_type == OP_CHANGE) {
        // Delete the lines except the first one.  Temporarily move the
        // cursor to the next line.  Save the current line number, if the
        // last line is deleted it may be changed.
  
        if (oap->line_count > 1) {
          lnum = curwin->w_cursor.lnum;
          ++curwin->w_cursor.lnum;
          del_lines(oap->line_count - 1, TRUE);
          curwin->w_cursor.lnum = lnum;
        }
        if (u_save_cursor() == FAIL)
          return FAIL;
        if (curbuf->b_p_ai) {                 // don't delete indent
          beginline(BL_WHITE);                // cursor on first non-white
          did_ai = true;                      // delete the indent when ESC hit
          ai_col = curwin->w_cursor.col;
        } else {
          beginline(0);                       // cursor in column 0
        }
  
        int old_len = (int)STRLEN(ml_get(curwin->w_cursor.lnum));
        truncate_line(false);         // delete the rest of the line
  
        extmark_splice_cols(curbuf,
                            (int)curwin->w_cursor.lnum-1, curwin->w_cursor.col,
                            old_len - curwin->w_cursor.col, 0, kExtmarkUndo);
  
                                      // leave cursor past last char in line
        if (oap->line_count > 1) {
          u_clearline();              // "U" command not possible after "2cc"
        }
      } else {
        del_lines(oap->line_count, TRUE);
        beginline(BL_WHITE | BL_FIX);
        u_clearline();            /* "U" command not possible after "dd" */
      }
    } else {
      if (virtual_op) {
        int endcol = 0;
  
        /* For virtualedit: break the tabs that are partly included. */
        if (gchar_pos(&oap->start) == '\t') {
          if (u_save_cursor() == FAIL)            /* save first line for undo */
            return FAIL;
          if (oap->line_count == 1)
            endcol = getviscol2(oap->end.col, oap->end.coladd);
          coladvance_force(getviscol2(oap->start.col, oap->start.coladd));
          oap->start = curwin->w_cursor;
          if (oap->line_count == 1) {
            coladvance(endcol);
            oap->end.col = curwin->w_cursor.col;
            oap->end.coladd = curwin->w_cursor.coladd;
            curwin->w_cursor = oap->start;
          }
        }
  
        /* Break a tab only when it's included in the area. */
        if (gchar_pos(&oap->end) == '\t'
            && oap->end.coladd == 0
            && oap->inclusive) {
          /* save last line for undo */
          if (u_save((linenr_T)(oap->end.lnum - 1),
                  (linenr_T)(oap->end.lnum + 1)) == FAIL)
            return FAIL;
          curwin->w_cursor = oap->end;
          coladvance_force(getviscol2(oap->end.col, oap->end.coladd));
          oap->end = curwin->w_cursor;
          curwin->w_cursor = oap->start;
        }
        mb_adjust_opend(oap);
      }
  
      if (oap->line_count == 1) {         /* delete characters within one line */
        if (u_save_cursor() == FAIL)              /* save line for undo */
          return FAIL;
  
        /* if 'cpoptions' contains '$', display '$' at end of change */
        if (           vim_strchr(p_cpo, CPO_DOLLAR) != NULL
                       && oap->op_type == OP_CHANGE
                       && oap->end.lnum == curwin->w_cursor.lnum
                       && !oap->is_VIsual
                       )
          display_dollar(oap->end.col - !oap->inclusive);
  
        n = oap->end.col - oap->start.col + 1 - !oap->inclusive;
  
        if (virtual_op) {
          /* fix up things for virtualedit-delete:
           * break the tabs which are going to get in our way
           */
          char_u          *curline = get_cursor_line_ptr();
          int len = (int)STRLEN(curline);
  
          if (oap->end.coladd != 0
              && (int)oap->end.col >= len - 1
              && !(oap->start.coladd && (int)oap->end.col >= len - 1))
            n++;
          /* Delete at least one char (e.g, when on a control char). */
          if (n == 0 && oap->start.coladd != oap->end.coladd)
            n = 1;
  
          /* When deleted a char in the line, reset coladd. */
          if (gchar_cursor() != NUL)
            curwin->w_cursor.coladd = 0;
        }
  
        (void)del_bytes((colnr_T)n, !virtual_op,
                        oap->op_type == OP_DELETE && !oap->is_VIsual);
      } else {
        // delete characters between lines
        pos_T curpos;
  
        /* save deleted and changed lines for undo */
        if (u_save((linenr_T)(curwin->w_cursor.lnum - 1),
                (linenr_T)(curwin->w_cursor.lnum + oap->line_count)) == FAIL)
          return FAIL;
  
        curbuf_splice_pending++;
        pos_T startpos = curwin->w_cursor;  // start position for delete
        truncate_line(true);        // delete from cursor to end of line
  
        curpos = curwin->w_cursor;  // remember curwin->w_cursor
        curwin->w_cursor.lnum++;
        del_lines(oap->line_count - 2, false);
        bcount_t deleted_bytes = (bcount_t)curbuf->deleted_bytes2 - startpos.col;
  
        // delete from start of line until op_end
        n = (oap->end.col + 1 - !oap->inclusive);
        curwin->w_cursor.col = 0;
        (void)del_bytes((colnr_T)n, !virtual_op,
                        oap->op_type == OP_DELETE && !oap->is_VIsual);
        deleted_bytes += n;
        curwin->w_cursor = curpos;  // restore curwin->w_cursor
        (void)do_join(2, false, false, false, false);
        curbuf_splice_pending--;
        extmark_splice(curbuf, (int)startpos.lnum-1, startpos.col,
                       (int)oap->line_count-1, n, deleted_bytes,
                       0, 0, 0, kExtmarkUndo);
      }
    }
  
    msgmore(curbuf->b_ml.ml_line_count - old_lcount);
  
  setmarks:
    if (oap->motion_type == kMTBlockWise) {
      curbuf->b_op_end.lnum = oap->end.lnum;
      curbuf->b_op_end.col = oap->start.col;
    } else {
      curbuf->b_op_end = oap->start;
    }
    curbuf->b_op_start = oap->start;
  
    return OK;
  }
  
  /*
   * Adjust end of operating area for ending on a multi-byte character.
   * Used for deletion.
   */
  static void mb_adjust_opend(oparg_T *oap)
  {
    char_u      *p;
  
    if (oap->inclusive) {
      p = ml_get(oap->end.lnum);
      oap->end.col += mb_tail_off(p, p + oap->end.col);
    }
  }
  
  /*
   * Put character 'c' at position 'lp'
   */
  static inline void pbyte(pos_T lp, int c)
  {
    assert(c <= UCHAR_MAX);
    *(ml_get_buf(curbuf, lp.lnum, true) + lp.col) = (char_u)c;
    if (!curbuf_splice_pending) {
      extmark_splice_cols(curbuf, (int)lp.lnum-1, lp.col, 1, 1, kExtmarkUndo);
    }
  }
  
  // Replace the character under the cursor with "c".
  // This takes care of multi-byte characters.
  static void replace_character(int c)
  {
    const int n = State;
  
    State = REPLACE;
    ins_char(c);
    State = n;
    // Backup to the replaced character.
    dec_cursor();
  }
  
  /*
   * Replace a whole area with one character.
   */
  int op_replace(oparg_T *oap, int c)
  {
    int n, numc;
    int num_chars;
    char_u              *newp, *oldp;
    colnr_T oldlen;
    struct block_def bd;
    char_u              *after_p = NULL;
    int had_ctrl_v_cr = false;
  
    if ((curbuf->b_ml.ml_flags & ML_EMPTY ) || oap->empty)
      return OK;              /* nothing to do */
  
    if (c == REPLACE_CR_NCHAR) {
      had_ctrl_v_cr = true;
      c = CAR;
    } else if (c == REPLACE_NL_NCHAR) {
      had_ctrl_v_cr = true;
      c = NL;
    }
  
    mb_adjust_opend(oap);
  
    if (u_save((linenr_T)(oap->start.lnum - 1),
            (linenr_T)(oap->end.lnum + 1)) == FAIL)
      return FAIL;
  
    /*
     * block mode replace
     */
    if (oap->motion_type == kMTBlockWise) {
      bd.is_MAX = (curwin->w_curswant == MAXCOL);
      for (; curwin->w_cursor.lnum <= oap->end.lnum; curwin->w_cursor.lnum++) {
        curwin->w_cursor.col = 0;       // make sure cursor position is valid
        block_prep(oap, &bd, curwin->w_cursor.lnum, true);
        if (bd.textlen == 0 && (!virtual_op || bd.is_MAX)) {
          continue;                     // nothing to replace
        }
  
        /* n == number of extra chars required
         * If we split a TAB, it may be replaced by several characters.
         * Thus the number of characters may increase!
         */
        /* If the range starts in virtual space, count the initial
         * coladd offset as part of "startspaces" */
        if (virtual_op && bd.is_short && *bd.textstart == NUL) {
          pos_T vpos;
  
          vpos.lnum = curwin->w_cursor.lnum;
          getvpos(&vpos, oap->start_vcol);
          bd.startspaces += vpos.coladd;
          n = bd.startspaces;
        } else
          /* allow for pre spaces */
          n = (bd.startspaces ? bd.start_char_vcols - 1 : 0);
  
        /* allow for post spp */
        n += (bd.endspaces
              && !bd.is_oneChar
              && bd.end_char_vcols > 0) ? bd.end_char_vcols - 1 : 0;
        /* Figure out how many characters to replace. */
        numc = oap->end_vcol - oap->start_vcol + 1;
        if (bd.is_short && (!virtual_op || bd.is_MAX))
          numc -= (oap->end_vcol - bd.end_vcol) + 1;
  
        /* A double-wide character can be replaced only up to half the
         * times. */
        if ((*mb_char2cells)(c) > 1) {
          if ((numc & 1) && !bd.is_short) {
            ++bd.endspaces;
            ++n;
          }
          numc = numc / 2;
        }
  
        /* Compute bytes needed, move character count to num_chars. */
        num_chars = numc;
        numc *= (*mb_char2len)(c);
  
        oldp = get_cursor_line_ptr();
        oldlen = (int)STRLEN(oldp);
  
        size_t newp_size = (size_t)bd.textcol + (size_t)bd.startspaces;
        if (had_ctrl_v_cr || (c != '\r' && c != '\n')) {
          newp_size += (size_t)numc;
          if (!bd.is_short) {
            newp_size += (size_t)(bd.endspaces + oldlen
                                  - bd.textcol - bd.textlen);
          }
        }
        newp = xmallocz(newp_size);
        // copy up to deleted part
        memmove(newp, oldp, (size_t)bd.textcol);
        oldp += bd.textcol + bd.textlen;
        // insert pre-spaces
        memset(newp + bd.textcol, ' ', (size_t)bd.startspaces);
        // insert replacement chars CHECK FOR ALLOCATED SPACE
        // REPLACE_CR_NCHAR/REPLACE_NL_NCHAR is used for entering CR literally.
        size_t after_p_len = 0;
        int col = oldlen - bd.textcol - bd.textlen + 1;
        assert(col >= 0);
        int newrows = 0, newcols = 0;
        if (had_ctrl_v_cr || (c != '\r' && c != '\n')) {
            // strlen(newp) at this point
            int newp_len = bd.textcol + bd.startspaces;
            while (--num_chars >= 0) {
              newp_len += utf_char2bytes(c, newp + newp_len);
            }
            if (!bd.is_short) {
              // insert post-spaces
              memset(newp + newp_len, ' ', (size_t)bd.endspaces);
              newp_len += bd.endspaces;
              // copy the part after the changed part
              memmove(newp + newp_len, oldp, (size_t)col);
            }
            newcols = newp_len - bd.textcol;
        } else {
          // Replacing with \r or \n means splitting the line.
          after_p_len = (size_t)col;
          after_p = (char_u *)xmalloc(after_p_len);
          memmove(after_p, oldp, after_p_len);
          newrows = 1;
        }
        // replace the line
        ml_replace(curwin->w_cursor.lnum, newp, false);
        curbuf_splice_pending++;
        linenr_T baselnum = curwin->w_cursor.lnum;
        if (after_p != NULL) {
          ml_append(curwin->w_cursor.lnum++, after_p, (int)after_p_len, false);
          appended_lines_mark(curwin->w_cursor.lnum, 1L);
          oap->end.lnum++;
          xfree(after_p);
        }
        curbuf_splice_pending--;
        extmark_splice(curbuf, (int)baselnum-1, bd.textcol,
                       0, bd.textlen, bd.textlen,
                       newrows, newcols, newrows+newcols, kExtmarkUndo);
      }
    } else {
      // Characterwise or linewise motion replace.
      if (oap->motion_type == kMTLineWise) {
        oap->start.col = 0;
        curwin->w_cursor.col = 0;
        oap->end.col = (colnr_T)STRLEN(ml_get(oap->end.lnum));
        if (oap->end.col)
          --oap->end.col;
      } else if (!oap->inclusive)
        dec(&(oap->end));
  
      // TODO(bfredl): we could batch all the splicing
      // done on the same line, at least
      while (ltoreq(curwin->w_cursor, oap->end)) {
        n = gchar_cursor();
        if (n != NUL) {
          if ((*mb_char2len)(c) > 1 || (*mb_char2len)(n) > 1) {
            /* This is slow, but it handles replacing a single-byte
             * with a multi-byte and the other way around. */
            if (curwin->w_cursor.lnum == oap->end.lnum)
              oap->end.col += (*mb_char2len)(c) - (*mb_char2len)(n);
            replace_character(c);
          } else {
            if (n == TAB) {
              int end_vcol = 0;
  
              if (curwin->w_cursor.lnum == oap->end.lnum) {
                /* oap->end has to be recalculated when
                 * the tab breaks */
                end_vcol = getviscol2(oap->end.col,
                    oap->end.coladd);
              }
              coladvance_force(getviscol());
              if (curwin->w_cursor.lnum == oap->end.lnum)
                getvpos(&oap->end, end_vcol);
            }
            pbyte(curwin->w_cursor, c);
          }
        } else if (virtual_op && curwin->w_cursor.lnum == oap->end.lnum) {
          int virtcols = oap->end.coladd;
  
          if (curwin->w_cursor.lnum == oap->start.lnum
              && oap->start.col == oap->end.col && oap->start.coladd)
            virtcols -= oap->start.coladd;
  
          /* oap->end has been trimmed so it's effectively inclusive;
           * as a result an extra +1 must be counted so we don't
           * trample the NUL byte. */
          coladvance_force(getviscol2(oap->end.col, oap->end.coladd) + 1);
          curwin->w_cursor.col -= (virtcols + 1);
          for (; virtcols >= 0; virtcols--) {
            if (utf_char2len(c) > 1) {
              replace_character(c);
            } else {
              pbyte(curwin->w_cursor, c);
            }
            if (inc(&curwin->w_cursor) == -1) {
              break;
            }
          }
        }
  
        /* Advance to next character, stop at the end of the file. */
        if (inc_cursor() == -1)
          break;
      }
    }
  
    curwin->w_cursor = oap->start;
    check_cursor();
    changed_lines(oap->start.lnum, oap->start.col, oap->end.lnum + 1, 0L, true);
  
    /* Set "'[" and "']" marks. */
    curbuf->b_op_start = oap->start;
    curbuf->b_op_end = oap->end;
  
    return OK;
  }
  
  
  /*
   * Handle the (non-standard vi) tilde operator.  Also for "gu", "gU" and "g?".
   */
  void op_tilde(oparg_T *oap)
  {
    pos_T pos;
    struct block_def bd;
    int did_change = FALSE;
  
    if (u_save((linenr_T)(oap->start.lnum - 1),
            (linenr_T)(oap->end.lnum + 1)) == FAIL)
      return;
  
    pos = oap->start;
    if (oap->motion_type == kMTBlockWise) {  // Visual block mode
      for (; pos.lnum <= oap->end.lnum; pos.lnum++) {
        int one_change;
  
        block_prep(oap, &bd, pos.lnum, false);
        pos.col = bd.textcol;
        one_change = swapchars(oap->op_type, &pos, bd.textlen);
        did_change |= one_change;
  
      }
      if (did_change) {
        changed_lines(oap->start.lnum, 0, oap->end.lnum + 1, 0L, true);
      }
    } else {  // not block mode
      if (oap->motion_type == kMTLineWise) {
        oap->start.col = 0;
        pos.col = 0;
        oap->end.col = (colnr_T)STRLEN(ml_get(oap->end.lnum));
        if (oap->end.col)
          --oap->end.col;
      } else if (!oap->inclusive)
        dec(&(oap->end));
  
      if (pos.lnum == oap->end.lnum)
        did_change = swapchars(oap->op_type, &pos,
            oap->end.col - pos.col + 1);
      else
        for (;; ) {
          did_change |= swapchars(oap->op_type, &pos,
              pos.lnum == oap->end.lnum ? oap->end.col + 1 :
              (int)STRLEN(ml_get_pos(&pos)));
          if (ltoreq(oap->end, pos) || inc(&pos) == -1)
            break;
        }
      if (did_change) {
        changed_lines(oap->start.lnum, oap->start.col, oap->end.lnum + 1,
                      0L, true);
      }
    }
  
    if (!did_change && oap->is_VIsual)
      /* No change: need to remove the Visual selection */
      redraw_curbuf_later(INVERTED);
  
    /*
     * Set '[ and '] marks.
     */
    curbuf->b_op_start = oap->start;
    curbuf->b_op_end = oap->end;
  
    if (oap->line_count > p_report) {
      if (oap->line_count == 1)
        MSG(_("1 line changed"));
      else
        smsg(_("%" PRId64 " lines changed"), (int64_t)oap->line_count);
    }
  }
  
  /*
   * Invoke swapchar() on "length" bytes at position "pos".
   * "pos" is advanced to just after the changed characters.
   * "length" is rounded up to include the whole last multi-byte character.
   * Also works correctly when the number of bytes changes.
   * Returns TRUE if some character was changed.
   */
  static int swapchars(int op_type, pos_T *pos, int length)
    FUNC_ATTR_NONNULL_ALL
  {
    int did_change = 0;
  
    for (int todo = length; todo > 0; todo--) {
      const int len = utfc_ptr2len(ml_get_pos(pos));
  
      // we're counting bytes, not characters
      if (len > 0) {
        todo -= len - 1;
      }
      did_change |= swapchar(op_type, pos);
      if (inc(pos) == -1)        /* at end of file */
        break;
    }
    return did_change;
  }
  
  // If op_type == OP_UPPER: make uppercase,
  // if op_type == OP_LOWER: make lowercase,
  // if op_type == OP_ROT13: do rot13 encoding,
  // else swap case of character at 'pos'
  // returns true when something actually changed.
  bool swapchar(int op_type, pos_T *pos)
    FUNC_ATTR_NONNULL_ARG(2)
  {
    const int c = gchar_pos(pos);
  
    // Only do rot13 encoding for ASCII characters.
    if (c >= 0x80 && op_type == OP_ROT13) {
      return false;
    }
  
    if (op_type == OP_UPPER && c == 0xdf) {
      pos_T sp = curwin->w_cursor;
  
      /* Special handling of German sharp s: change to "SS". */
      curwin->w_cursor = *pos;
      del_char(false);
      ins_char('S');
      ins_char('S');
      curwin->w_cursor = sp;
      inc(pos);
    }
  
    int nc = c;
    if (mb_islower(c)) {
      if (op_type == OP_ROT13) {
        nc = ROT13(c, 'a');
      } else if (op_type != OP_LOWER) {
        nc = mb_toupper(c);
      }
    } else if (mb_isupper(c)) {
      if (op_type == OP_ROT13) {
        nc = ROT13(c, 'A');
      } else if (op_type != OP_UPPER) {
        nc = mb_tolower(c);
      }
    }
    if (nc != c) {
      if (c >= 0x80 || nc >= 0x80) {
        pos_T sp = curwin->w_cursor;
  
        curwin->w_cursor = *pos;
        // don't use del_char(), it also removes composing chars
        del_bytes(utf_ptr2len(get_cursor_pos_ptr()), false, false);
        ins_char(nc);
        curwin->w_cursor = sp;
      } else {
        pbyte(*pos, nc);
      }
      return true;
    }
    return false;
  }
  
  /*
   * op_insert - Insert and append operators for Visual mode.
   */
  void op_insert(oparg_T *oap, long count1)
  {
    long ins_len, pre_textlen = 0;
    char_u              *firstline, *ins_text;
    colnr_T ind_pre = 0;
    struct block_def bd;
    int i;
    pos_T t1;
  
    /* edit() changes this - record it for OP_APPEND */
    bd.is_MAX = (curwin->w_curswant == MAXCOL);
  
    /* vis block is still marked. Get rid of it now. */
    curwin->w_cursor.lnum = oap->start.lnum;
    update_screen(INVERTED);
  
    if (oap->motion_type == kMTBlockWise) {
      // When 'virtualedit' is used, need to insert the extra spaces before
      // doing block_prep().  When only "block" is used, virtual edit is
      // already disabled, but still need it when calling
      // coladvance_force().
      if (curwin->w_cursor.coladd > 0) {
        unsigned old_ve_flags = ve_flags;
  
        ve_flags = VE_ALL;
        if (u_save_cursor() == FAIL)
          return;
        coladvance_force(oap->op_type == OP_APPEND
            ? oap->end_vcol + 1 : getviscol());
        if (oap->op_type == OP_APPEND)
          --curwin->w_cursor.col;
        ve_flags = old_ve_flags;
      }
      // Get the info about the block before entering the text
      block_prep(oap, &bd, oap->start.lnum, true);
      // Get indent information
      ind_pre = (colnr_T)getwhitecols_curline();
      firstline = ml_get(oap->start.lnum) + bd.textcol;
  
      if (oap->op_type == OP_APPEND) {
        firstline += bd.textlen;
      }
      pre_textlen = (long)STRLEN(firstline);
    }
  
    if (oap->op_type == OP_APPEND) {
      if (oap->motion_type == kMTBlockWise
          && curwin->w_cursor.coladd == 0
          ) {
        /* Move the cursor to the character right of the block. */
        curwin->w_set_curswant = TRUE;
        while (*get_cursor_pos_ptr() != NUL
               && (curwin->w_cursor.col < bd.textcol + bd.textlen))
          ++curwin->w_cursor.col;
        if (bd.is_short && !bd.is_MAX) {
          /* First line was too short, make it longer and adjust the
           * values in "bd". */
          if (u_save_cursor() == FAIL)
            return;
          for (i = 0; i < bd.endspaces; i++) {
            ins_char(' ');
          }
          bd.textlen += bd.endspaces;
        }
      } else {
        curwin->w_cursor = oap->end;
        check_cursor_col();
  
        // Works just like an 'i'nsert on the next character.
        if (!LINEEMPTY(curwin->w_cursor.lnum)
            && oap->start_vcol != oap->end_vcol) {
          inc_cursor();
        }
      }
    }
  
    t1 = oap->start;
    (void)edit(NUL, false, (linenr_T)count1);
  
    // When a tab was inserted, and the characters in front of the tab
    // have been converted to a tab as well, the column of the cursor
    // might have actually been reduced, so need to adjust here. */
    if (t1.lnum == curbuf->b_op_start_orig.lnum
        && lt(curbuf->b_op_start_orig, t1)) {
      oap->start = curbuf->b_op_start_orig;
    }
  
    /* If user has moved off this line, we don't know what to do, so do
     * nothing.
     * Also don't repeat the insert when Insert mode ended with CTRL-C. */
    if (curwin->w_cursor.lnum != oap->start.lnum || got_int)
      return;
  
    if (oap->motion_type == kMTBlockWise) {
      struct block_def bd2;
      bool did_indent = false;
  
      // if indent kicked in, the firstline might have changed
      // but only do that, if the indent actually increased
      const colnr_T ind_post = (colnr_T)getwhitecols_curline();
      if (curbuf->b_op_start.col > ind_pre && ind_post > ind_pre) {
        bd.textcol += ind_post - ind_pre;
        bd.start_vcol += ind_post - ind_pre;
        did_indent = true;
      }
  
      // The user may have moved the cursor before inserting something, try
      // to adjust the block for that.  But only do it, if the difference
      // does not come from indent kicking in.
      if (oap->start.lnum == curbuf->b_op_start_orig.lnum
          && !bd.is_MAX
          && !did_indent) {
        if (oap->op_type == OP_INSERT
            && oap->start.col + oap->start.coladd
            != curbuf->b_op_start_orig.col + curbuf->b_op_start_orig.coladd) {
          int t = getviscol2(curbuf->b_op_start_orig.col,
                             curbuf->b_op_start_orig.coladd);
          oap->start.col = curbuf->b_op_start_orig.col;
          pre_textlen -= t - oap->start_vcol;
          oap->start_vcol = t;
        } else if (oap->op_type == OP_APPEND
                   && oap->end.col + oap->end.coladd
                   >= curbuf->b_op_start_orig.col
                   + curbuf->b_op_start_orig.coladd) {
          int t = getviscol2(curbuf->b_op_start_orig.col,
                             curbuf->b_op_start_orig.coladd);
          oap->start.col = curbuf->b_op_start_orig.col;
          /* reset pre_textlen to the value of OP_INSERT */
          pre_textlen += bd.textlen;
          pre_textlen -= t - oap->start_vcol;
          oap->start_vcol = t;
          oap->op_type = OP_INSERT;
        }
      }
  
      /*
       * Spaces and tabs in the indent may have changed to other spaces and
       * tabs.  Get the starting column again and correct the length.
       * Don't do this when "$" used, end-of-line will have changed.
       */
      block_prep(oap, &bd2, oap->start.lnum, true);
      if (!bd.is_MAX || bd2.textlen < bd.textlen) {
        if (oap->op_type == OP_APPEND) {
          pre_textlen += bd2.textlen - bd.textlen;
          if (bd2.endspaces)
            --bd2.textlen;
        }
        bd.textcol = bd2.textcol;
        bd.textlen = bd2.textlen;
      }
  
      /*
       * Subsequent calls to ml_get() flush the firstline data - take a
       * copy of the required string.
       */
      firstline = ml_get(oap->start.lnum);
      const size_t len = STRLEN(firstline);
      colnr_T add = bd.textcol;
      if (oap->op_type == OP_APPEND) {
        add += bd.textlen;
      }
      if ((size_t)add > len) {
        firstline += len;  // short line, point to the NUL
      } else {
        firstline += add;
      }
      ins_len = (long)STRLEN(firstline) - pre_textlen;
      if (pre_textlen >= 0 && ins_len > 0) {
        ins_text = vim_strnsave(firstline, (size_t)ins_len);
        // block handled here
        if (u_save(oap->start.lnum, (linenr_T)(oap->end.lnum + 1)) == OK) {
          block_insert(oap, ins_text, (oap->op_type == OP_INSERT), &bd);
        }
  
        curwin->w_cursor.col = oap->start.col;
        check_cursor();
        xfree(ins_text);
      }
    }
  }
  
  /*
   * op_change - handle a change operation
   *
   * return TRUE if edit() returns because of a CTRL-O command
   */
  int op_change(oparg_T *oap)
  {
    colnr_T l;
    int retval;
    long offset;
    linenr_T linenr;
    long ins_len;
    long pre_textlen = 0;
    long pre_indent = 0;
    char_u *newp;
    char_u *firstline;
    char_u *ins_text;
    char_u *oldp;
    struct block_def bd;
  
    l = oap->start.col;
    if (oap->motion_type == kMTLineWise) {
      l = 0;
      if (!p_paste && curbuf->b_p_si
          && !curbuf->b_p_cin
          )
        can_si = true;            // It's like opening a new line, do si
    }
  
    /* First delete the text in the region.  In an empty buffer only need to
     * save for undo */
    if (curbuf->b_ml.ml_flags & ML_EMPTY) {
      if (u_save_cursor() == FAIL)
        return FALSE;
    } else if (op_delete(oap) == FAIL)
      return FALSE;
  
    if ((l > curwin->w_cursor.col) && !LINEEMPTY(curwin->w_cursor.lnum)
        && !virtual_op) {
      inc_cursor();
    }
  
    // check for still on same line (<CR> in inserted text meaningless)
    // skip blank lines too
    if (oap->motion_type == kMTBlockWise) {
      // Add spaces before getting the current line length.
      if (virtual_op && (curwin->w_cursor.coladd > 0
                         || gchar_cursor() == NUL)) {
        coladvance_force(getviscol());
      }
      firstline = ml_get(oap->start.lnum);
      pre_textlen = (long)STRLEN(firstline);
      pre_indent = (long)getwhitecols(firstline);
      bd.textcol = curwin->w_cursor.col;
    }
  
    if (oap->motion_type == kMTLineWise) {
      fix_indent();
    }
  
    retval = edit(NUL, FALSE, (linenr_T)1);
  
    /*
     * In Visual block mode, handle copying the new text to all lines of the
     * block.
     * Don't repeat the insert when Insert mode ended with CTRL-C.
     */
    if (oap->motion_type == kMTBlockWise
        && oap->start.lnum != oap->end.lnum && !got_int) {
      // Auto-indenting may have changed the indent.  If the cursor was past
      // the indent, exclude that indent change from the inserted text.
      firstline = ml_get(oap->start.lnum);
      if (bd.textcol > (colnr_T)pre_indent) {
        long new_indent = (long)getwhitecols(firstline);
  
        pre_textlen += new_indent - pre_indent;
        bd.textcol += (colnr_T)(new_indent - pre_indent);
      }
  
      ins_len = (long)STRLEN(firstline) - pre_textlen;
      if (ins_len > 0) {
        /* Subsequent calls to ml_get() flush the firstline data - take a
         * copy of the inserted text.  */
        ins_text = (char_u *)xmalloc((size_t)(ins_len + 1));
        STRLCPY(ins_text, firstline + bd.textcol, ins_len + 1);
        for (linenr = oap->start.lnum + 1; linenr <= oap->end.lnum;
             linenr++) {
          block_prep(oap, &bd, linenr, true);
          if (!bd.is_short || virtual_op) {
            pos_T vpos;
  
            /* If the block starts in virtual space, count the
             * initial coladd offset as part of "startspaces" */
            if (bd.is_short) {
              vpos.lnum = linenr;
              (void)getvpos(&vpos, oap->start_vcol);
            } else {
              vpos.coladd = 0;
            }
            oldp = ml_get(linenr);
            newp = xmalloc(STRLEN(oldp) + (size_t)vpos.coladd
                           + (size_t)ins_len + 1);
            // copy up to block start
            memmove(newp, oldp, (size_t)bd.textcol);
            offset = bd.textcol;
            memset(newp + offset, ' ', (size_t)vpos.coladd);
            offset += vpos.coladd;
            memmove(newp + offset, ins_text, (size_t)ins_len);
            offset += ins_len;
            oldp += bd.textcol;
            STRMOVE(newp + offset, oldp);
            ml_replace(linenr, newp, false);
            extmark_splice_cols(curbuf, (int)linenr-1, bd.textcol,
                                0, vpos.coladd+(int)ins_len, kExtmarkUndo);
          }
        }
        check_cursor();
        changed_lines(oap->start.lnum + 1, 0, oap->end.lnum + 1, 0L, true);
        xfree(ins_text);
      }
    }
  
    return retval;
  }
  
  /*
   * set all the yank registers to empty (called from main())
   */
  void init_yank(void)
  {
    memset(&(y_regs[0]), 0, sizeof(y_regs));
  }
  
  #if defined(EXITFREE)
  void clear_registers(void)
  {
    int i;
  
    for (i = 0; i < NUM_REGISTERS; i++) {
      free_register(&y_regs[i]);
    }
  }
  
  #endif
  
  
   /// Free contents of yankreg `reg`.
   /// Called for normal freeing and in case of error.
   /// `reg` must not be NULL (but `reg->y_array` might be)
  void free_register(yankreg_T *reg)
    FUNC_ATTR_NONNULL_ALL
  {
    set_yreg_additional_data(reg, NULL);
    if (reg->y_array != NULL) {
      for (size_t i = reg->y_size; i-- > 0;) {  // from y_size - 1 to 0 included
        xfree(reg->y_array[i]);
      }
      XFREE_CLEAR(reg->y_array);
    }
  }
  
  /// Yanks the text between "oap->start" and "oap->end" into a yank register.
  /// If we are to append (uppercase register), we first yank into a new yank
  /// register and then concatenate the old and the new one.
  ///
  /// @param oap operator arguments
  /// @param message show message when more than `&report` lines are yanked.
  /// @param deleting whether the function was called from a delete operation.
  /// @returns whether the operation register was writable.
  bool op_yank(oparg_T *oap, bool message, int deleting)
    FUNC_ATTR_NONNULL_ALL
  {
    // check for read-only register
    if (oap->regname != 0 && !valid_yank_reg(oap->regname, true)) {
      beep_flush();
      return false;
    }
    if (oap->regname == '_') {
      return true; // black hole: nothing to do
    }
  
    yankreg_T *reg = get_yank_register(oap->regname, YREG_YANK);
    op_yank_reg(oap, message, reg, is_append_register(oap->regname));
    // op_delete will set_clipboard and do_autocmd
    if (!deleting) {
      set_clipboard(oap->regname, reg);
      do_autocmd_textyankpost(oap, reg);
    }
  
    return true;
  }
  
  static void op_yank_reg(oparg_T *oap, bool message, yankreg_T *reg, bool append)
  {
    yankreg_T newreg;  // new yank register when appending
    char_u **new_ptr;
    linenr_T lnum;     // current line number
    size_t j;
    MotionType yank_type = oap->motion_type;
    size_t yanklines = (size_t)oap->line_count;
    linenr_T yankendlnum = oap->end.lnum;
    char_u *p;
    char_u *pnew;
    struct block_def bd;
  
    yankreg_T *curr = reg;  // copy of current register
    // append to existing contents
    if (append && reg->y_array != NULL) {
      reg = &newreg;
    } else {
      free_register(reg);  // free previously yanked lines
    }
  
    // If the cursor was in column 1 before and after the movement, and the
    // operator is not inclusive, the yank is always linewise.
    if (oap->motion_type == kMTCharWise
        && oap->start.col == 0
        && !oap->inclusive
        && (!oap->is_VIsual || *p_sel == 'o')
        && oap->end.col == 0
        && yanklines > 1) {
      yank_type = kMTLineWise;
      yankendlnum--;
      yanklines--;
    }
  
    reg->y_size = yanklines;
    reg->y_type = yank_type;  // set the yank register type
    reg->y_width = 0;
    reg->y_array = xcalloc(yanklines, sizeof(char_u *));
    reg->additional_data = NULL;
    reg->timestamp = os_time();
  
    size_t y_idx = 0;  // index in y_array[]
    lnum = oap->start.lnum;
  
    if (yank_type == kMTBlockWise) {
      // Visual block mode
      reg->y_width = oap->end_vcol - oap->start_vcol;
  
      if (curwin->w_curswant == MAXCOL && reg->y_width > 0)
        reg->y_width--;
    }
  
    for (; lnum <= yankendlnum; lnum++, y_idx++) {
      switch (reg->y_type) {
      case kMTBlockWise:
        block_prep(oap, &bd, lnum, false);
        yank_copy_line(reg, &bd, y_idx);
        break;
  
      case kMTLineWise:
        reg->y_array[y_idx] = vim_strsave(ml_get(lnum));
        break;
  
      case kMTCharWise:
      {
        colnr_T startcol = 0, endcol = MAXCOL;
        int is_oneChar = false;
        colnr_T cs, ce;
        p = ml_get(lnum);
        bd.startspaces = 0;
        bd.endspaces = 0;
  
        if (lnum == oap->start.lnum) {
          startcol = oap->start.col;
          if (virtual_op) {
            getvcol(curwin, &oap->start, &cs, NULL, &ce);
            if (ce != cs && oap->start.coladd > 0) {
              /* Part of a tab selected -- but don't
               * double-count it. */
              bd.startspaces = (ce - cs + 1)
                               - oap->start.coladd;
              startcol++;
            }
          }
        }
  
        if (lnum == oap->end.lnum) {
          endcol = oap->end.col;
          if (virtual_op) {
            getvcol(curwin, &oap->end, &cs, NULL, &ce);
            if (p[endcol] == NUL || (cs + oap->end.coladd < ce
                                     // Don't add space for double-wide
                                     // char; endcol will be on last byte
                                     // of multi-byte char.
                                     && utf_head_off(p, p + endcol) == 0)) {
              if (oap->start.lnum == oap->end.lnum
                  && oap->start.col == oap->end.col) {
                // Special case: inside a single char
                is_oneChar = true;
                bd.startspaces = oap->end.coladd
                                 - oap->start.coladd + oap->inclusive;
                endcol = startcol;
              } else {
                bd.endspaces = oap->end.coladd
                               + oap->inclusive;
                endcol -= oap->inclusive;
              }
            }
          }
        }
        if (endcol == MAXCOL)
          endcol = (colnr_T)STRLEN(p);
        if (startcol > endcol
            || is_oneChar
            ) {
          bd.textlen = 0;
        } else {
          bd.textlen = endcol - startcol + oap->inclusive;
        }
        bd.textstart = p + startcol;
        yank_copy_line(reg, &bd, y_idx);
        break;
      }
      // NOTREACHED
      case kMTUnknown:
          assert(false);
      }
    }
  
    if (curr != reg) {      /* append the new block to the old block */
      new_ptr = xmalloc(sizeof(char_u *) * (curr->y_size + reg->y_size));
      for (j = 0; j < curr->y_size; ++j)
        new_ptr[j] = curr->y_array[j];
      xfree(curr->y_array);
      curr->y_array = new_ptr;
  
      if (yank_type == kMTLineWise) {
        // kMTLineWise overrides kMTCharWise and kMTBlockWise
        curr->y_type = kMTLineWise;
      }
  
      // Concatenate the last line of the old block with the first line of
      // the new block, unless being Vi compatible.
      if (curr->y_type == kMTCharWise
          && vim_strchr(p_cpo, CPO_REGAPPEND) == NULL) {
        pnew = xmalloc(STRLEN(curr->y_array[curr->y_size - 1])
                       + STRLEN(reg->y_array[0]) + 1);
        STRCPY(pnew, curr->y_array[--j]);
        STRCAT(pnew, reg->y_array[0]);
        xfree(curr->y_array[j]);
        xfree(reg->y_array[0]);
        curr->y_array[j++] = pnew;
        y_idx = 1;
      } else
        y_idx = 0;
      while (y_idx < reg->y_size)
        curr->y_array[j++] = reg->y_array[y_idx++];
      curr->y_size = j;
      xfree(reg->y_array);
    }
    if (curwin->w_p_rnu) {
      redraw_later(SOME_VALID);  // cursor moved to start
    }
    if (message) {  // Display message about yank?
      if (yank_type == kMTCharWise && yanklines == 1) {
        yanklines = 0;
      }
      // Some versions of Vi use ">=" here, some don't...
      if (yanklines > (size_t)p_report) {
        char namebuf[100];
  
        if (oap->regname == NUL) {
          *namebuf = NUL;
        } else {
          vim_snprintf(namebuf, sizeof(namebuf), _(" into \"%c"), oap->regname);
        }
  
        // redisplay now, so message is not deleted
        update_topline_redraw();
        if (yanklines == 1) {
          if (yank_type == kMTBlockWise) {
            smsg(_("block of 1 line yanked%s"), namebuf);
          } else {
            smsg(_("1 line yanked%s"), namebuf);
          }
        } else if (yank_type == kMTBlockWise) {
          smsg(_("block of %" PRId64 " lines yanked%s"),
               (int64_t)yanklines, namebuf);
        } else {
          smsg(_("%" PRId64 " lines yanked%s"), (int64_t)yanklines, namebuf);
        }
      }
    }
  
    /*
     * Set "'[" and "']" marks.
     */
    curbuf->b_op_start = oap->start;
    curbuf->b_op_end = oap->end;
    if (yank_type == kMTLineWise) {
      curbuf->b_op_start.col = 0;
      curbuf->b_op_end.col = MAXCOL;
    }
  
    return;
  }
  
  static void yank_copy_line(yankreg_T *reg, struct block_def *bd, size_t y_idx)
  {
    int size = bd->startspaces + bd->endspaces + bd->textlen;
    assert(size >= 0);
    char_u *pnew = xmallocz((size_t)size);
    reg->y_array[y_idx] = pnew;
    memset(pnew, ' ', (size_t)bd->startspaces);
    pnew += bd->startspaces;
    memmove(pnew, bd->textstart, (size_t)bd->textlen);
    pnew += bd->textlen;
    memset(pnew, ' ', (size_t)bd->endspaces);
    pnew += bd->endspaces;
    *pnew = NUL;
  }
  
  /// Execute autocommands for TextYankPost.
  ///
  /// @param oap Operator arguments.
  /// @param reg The yank register used.
  static void do_autocmd_textyankpost(oparg_T *oap, yankreg_T *reg)
    FUNC_ATTR_NONNULL_ALL
  {
    static bool recursive = false;
  
    if (recursive || !has_event(EVENT_TEXTYANKPOST)) {
      // No autocommand was defined, or we yanked from this autocommand.
      return;
    }
  
    recursive = true;
  
    // Set the v:event dictionary with information about the yank.
    dict_T *dict = get_vim_var_dict(VV_EVENT);
  
    // The yanked text contents.
    list_T *const list = tv_list_alloc((ptrdiff_t)reg->y_size);
    for (size_t i = 0; i < reg->y_size; i++) {
      tv_list_append_string(list, (const char *)reg->y_array[i], -1);
    }
    tv_list_set_lock(list, VAR_FIXED);
    tv_dict_add_list(dict, S_LEN("regcontents"), list);
  
    // Register type.
    char buf[NUMBUFLEN+2];
    format_reg_type(reg->y_type, reg->y_width, buf, ARRAY_SIZE(buf));
    tv_dict_add_str(dict, S_LEN("regtype"), buf);
  
    // Name of requested register, or empty string for unnamed operation.
    buf[0] = (char)oap->regname;
    buf[1] = NUL;
    tv_dict_add_str(dict, S_LEN("regname"), buf);
  
    // Motion type: inclusive or exclusive.
    tv_dict_add_bool(dict, S_LEN("inclusive"),
                     oap->inclusive ? kBoolVarTrue : kBoolVarFalse);
  
    // Kind of operation: yank, delete, change).
    buf[0] = (char)get_op_char(oap->op_type);
    buf[1] = NUL;
    tv_dict_add_str(dict, S_LEN("operator"), buf);
  
    // Selection type: visual or not.
    tv_dict_add_bool(dict, S_LEN("visual"),
                     oap->is_VIsual ? kBoolVarTrue : kBoolVarFalse);
  
    tv_dict_set_keys_readonly(dict);
    textlock++;
    apply_autocmds(EVENT_TEXTYANKPOST, NULL, NULL, false, curbuf);
    textlock--;
    tv_dict_clear(dict);
  
    recursive = false;
  }
  
  /*
   * Put contents of register "regname" into the text.
   * Caller must check "regname" to be valid!
   * "flags": PUT_FIXINDENT     make indent look nice
   *          PUT_CURSEND       leave cursor after end of new text
   *          PUT_LINE          force linewise put (":put")
      dir: BACKWARD for 'P', FORWARD for 'p' */
  void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
  {
    char_u *ptr;
    char_u *newp;
    char_u *oldp;
    int yanklen;
    size_t totlen = 0;  // init for gcc
    linenr_T lnum = 0;
    colnr_T col = 0;
    size_t i;  // index in y_array[]
    MotionType y_type;
    size_t y_size;
    size_t oldlen;
    int y_width = 0;
    colnr_T vcol;
    int delcount;
    int incr = 0;
    struct block_def bd;
    char_u      **y_array = NULL;
    long nr_lines = 0;
    pos_T new_cursor;
    int indent;
    int orig_indent = 0;                  /* init for gcc */
    int indent_diff = 0;                  /* init for gcc */
    int first_indent = TRUE;
    int lendiff = 0;
    pos_T old_pos;
    char_u      *insert_string = NULL;
    bool allocated = false;
    long cnt;
  
    if (flags & PUT_FIXINDENT)
      orig_indent = get_indent();
  
    curbuf->b_op_start = curwin->w_cursor;        /* default for '[ mark */
    curbuf->b_op_end = curwin->w_cursor;          /* default for '] mark */
  
    /*
     * Using inserted text works differently, because the register includes
     * special characters (newlines, etc.).
     */
    if (regname == '.' && !reg) {
      bool non_linewise_vis = (VIsual_active && VIsual_mode != 'V');
  
      // PUT_LINE has special handling below which means we use 'i' to start.
      char command_start_char = non_linewise_vis ? 'c' :
        (flags & PUT_LINE ? 'i' : (dir == FORWARD ? 'a' : 'i'));
  
      // To avoid 'autoindent' on linewise puts, create a new line with `:put _`.
      if (flags & PUT_LINE) {
        do_put('_', NULL, dir, 1, PUT_LINE);
      }
  
      // If given a count when putting linewise, we stuff the readbuf with the
      // dot register 'count' times split by newlines.
      if (flags & PUT_LINE) {
        stuffcharReadbuff(command_start_char);
        for (; count > 0; count--) {
          (void)stuff_inserted(NUL, 1, count != 1);
          if (count != 1) {
            // To avoid 'autoindent' affecting the text, use Ctrl_U to remove any
            // whitespace. Can't just insert Ctrl_U into readbuf1, this would go
            // back to the previous line in the case of 'noautoindent' and
            // 'backspace' includes "eol". So we insert a dummy space for Ctrl_U
            // to consume.
            stuffReadbuff("\n ");
            stuffcharReadbuff(Ctrl_U);
          }
        }
      } else {
        (void)stuff_inserted(command_start_char, count, false);
      }
  
      // Putting the text is done later, so can't move the cursor to the next
      // character.  Simulate it with motion commands after the insert.
      if (flags & PUT_CURSEND) {
        if (flags & PUT_LINE) {
          stuffReadbuff("j0");
        } else {
          // Avoid ringing the bell from attempting to move into the space after
          // the current line. We can stuff the readbuffer with "l" if:
          // 1) 'virtualedit' is "all" or "onemore"
          // 2) We are not at the end of the line
          // 3) We are not  (one past the end of the line && on the last line)
          //    This allows a visual put over a selection one past the end of the
          //    line joining the current line with the one below.
  
          // curwin->w_cursor.col marks the byte position of the cursor in the
          // currunt line. It increases up to a max of
          // STRLEN(ml_get(curwin->w_cursor.lnum)). With 'virtualedit' and the
          // cursor past the end of the line, curwin->w_cursor.coladd is
          // incremented instead of curwin->w_cursor.col.
          char_u *cursor_pos = get_cursor_pos_ptr();
          bool one_past_line = (*cursor_pos == NUL);
          bool eol = false;
          if (!one_past_line) {
            eol = (*(cursor_pos + mb_ptr2len(cursor_pos)) == NUL);
          }
  
          bool ve_allows = (ve_flags == VE_ALL || ve_flags == VE_ONEMORE);
          bool eof = curbuf->b_ml.ml_line_count == curwin->w_cursor.lnum
                     && one_past_line;
          if (ve_allows || !(eol || eof)) {
            stuffcharReadbuff('l');
          }
        }
      } else if (flags & PUT_LINE) {
        stuffReadbuff("g'[");
      }
  
      // So the 'u' command restores cursor position after ".p, save the cursor
      // position now (though not saving any text).
      if (command_start_char == 'a') {
        if (u_save(curwin->w_cursor.lnum, curwin->w_cursor.lnum + 1) == FAIL) {
          return;
        }
      }
      return;
    }
  
    /*
     * For special registers '%' (file name), '#' (alternate file name) and
     * ':' (last command line), etc. we have to create a fake yank register.
     */
    if (!reg && get_spec_reg(regname, &insert_string, &allocated, true)) {
      if (insert_string == NULL) {
        return;
      }
    }
  
    if (!curbuf->terminal) {
      // Autocommands may be executed when saving lines for undo.  This might
      // make y_array invalid, so we start undo now to avoid that.
      if (u_save(curwin->w_cursor.lnum, curwin->w_cursor.lnum + 1) == FAIL) {
        return;
      }
    }
  
    if (insert_string != NULL) {
      y_type = kMTCharWise;
      if (regname == '=') {
        /* For the = register we need to split the string at NL
         * characters.
         * Loop twice: count the number of lines and save them. */
        for (;; ) {
          y_size = 0;
          ptr = insert_string;
          while (ptr != NULL) {
            if (y_array != NULL)
              y_array[y_size] = ptr;
            ++y_size;
            ptr = vim_strchr(ptr, '\n');
            if (ptr != NULL) {
              if (y_array != NULL)
                *ptr = NUL;
              ++ptr;
              /* A trailing '\n' makes the register linewise. */
              if (*ptr == NUL) {
                y_type = kMTLineWise;
                break;
              }
            }
          }
          if (y_array != NULL)
            break;
          y_array = (char_u **)xmalloc(y_size * sizeof(char_u *));
        }
      } else {
        y_size = 1;               /* use fake one-line yank register */
        y_array = &insert_string;
      }
    } else {
      // in case of replacing visually selected text
      // the yankreg might already have been saved to avoid
      // just restoring the deleted text.
      if (reg == NULL) {
        reg = get_yank_register(regname, YREG_PASTE);
      }
  
      y_type = reg->y_type;
      y_width = reg->y_width;
      y_size = reg->y_size;
      y_array = reg->y_array;
    }
  
    if (curbuf->terminal) {
      terminal_paste(count, y_array, y_size);
      return;
    }
  
    if (y_type == kMTLineWise) {
      if (flags & PUT_LINE_SPLIT) {
        // "p" or "P" in Visual mode: split the lines to put the text in
        // between.
        if (u_save_cursor() == FAIL) {
          goto end;
        }
        char_u *p = get_cursor_pos_ptr();
        if (dir == FORWARD && *p != NUL) {
          MB_PTR_ADV(p);
        }
        ptr = vim_strsave(p);
        ml_append(curwin->w_cursor.lnum, ptr, (colnr_T)0, false);
        xfree(ptr);
  
        oldp = get_cursor_line_ptr();
        p = oldp + curwin->w_cursor.col;
        if (dir == FORWARD && *p != NUL) {
          MB_PTR_ADV(p);
        }
        ptr = vim_strnsave(oldp, (size_t)(p - oldp));
        ml_replace(curwin->w_cursor.lnum, ptr, false);
        nr_lines++;
        dir = FORWARD;
      }
      if (flags & PUT_LINE_FORWARD) {
        /* Must be "p" for a Visual block, put lines below the block. */
        curwin->w_cursor = curbuf->b_visual.vi_end;
        dir = FORWARD;
      }
      curbuf->b_op_start = curwin->w_cursor;      /* default for '[ mark */
      curbuf->b_op_end = curwin->w_cursor;        /* default for '] mark */
    }
  
    if (flags & PUT_LINE) {  // :put command or "p" in Visual line mode.
      y_type = kMTLineWise;
    }
  
    if (y_size == 0 || y_array == NULL) {
      EMSG2(_("E353: Nothing in register %s"),
          regname == 0 ? (char_u *)"\"" : transchar(regname));
      goto end;
    }
  
    if (y_type == kMTBlockWise) {
      lnum = curwin->w_cursor.lnum + (linenr_T)y_size + 1;
      if (lnum > curbuf->b_ml.ml_line_count) {
        lnum = curbuf->b_ml.ml_line_count + 1;
      }
      if (u_save(curwin->w_cursor.lnum - 1, lnum) == FAIL) {
        goto end;
      }
    } else if (y_type == kMTLineWise) {
      lnum = curwin->w_cursor.lnum;
      // Correct line number for closed fold.  Don't move the cursor yet,
      // u_save() uses it.
      if (dir == BACKWARD) {
        (void)hasFolding(lnum, &lnum, NULL);
      } else {
        (void)hasFolding(lnum, NULL, &lnum);
      }
      if (dir == FORWARD) {
        lnum++;
      }
      // In an empty buffer the empty line is going to be replaced, include
      // it in the saved lines.
      if ((BUFEMPTY() ? u_save(0, 2) : u_save(lnum - 1, lnum)) == FAIL) {
        goto end;
      }
      if (dir == FORWARD) {
        curwin->w_cursor.lnum = lnum - 1;
      } else {
        curwin->w_cursor.lnum = lnum;
      }
      curbuf->b_op_start = curwin->w_cursor;      // for mark_adjust()
    } else if (u_save_cursor() == FAIL) {
      goto end;
    }
  
    yanklen = (int)STRLEN(y_array[0]);
  
    if (ve_flags == VE_ALL && y_type == kMTCharWise) {
      if (gchar_cursor() == TAB) {
        /* Don't need to insert spaces when "p" on the last position of a
         * tab or "P" on the first position. */
        if (dir == FORWARD
            ? (int)curwin->w_cursor.coladd < curbuf->b_p_ts - 1
            : curwin->w_cursor.coladd > 0)
          coladvance_force(getviscol());
        else
          curwin->w_cursor.coladd = 0;
      } else if (curwin->w_cursor.coladd > 0 || gchar_cursor() == NUL)
        coladvance_force(getviscol() + (dir == FORWARD));
    }
  
    lnum = curwin->w_cursor.lnum;
    col = curwin->w_cursor.col;
  
    /*
     * Block mode
     */
    if (y_type == kMTBlockWise) {
      int c = gchar_cursor();
      colnr_T endcol2 = 0;
  
      if (dir == FORWARD && c != NUL) {
        if (ve_flags == VE_ALL)
          getvcol(curwin, &curwin->w_cursor, &col, NULL, &endcol2);
        else
          getvcol(curwin, &curwin->w_cursor, NULL, NULL, &col);
  
        // move to start of next multi-byte character
        curwin->w_cursor.col += utfc_ptr2len(get_cursor_pos_ptr());
        col++;
      } else {
        getvcol(curwin, &curwin->w_cursor, &col, NULL, &endcol2);
      }
  
      col += curwin->w_cursor.coladd;
      if (ve_flags == VE_ALL
          && (curwin->w_cursor.coladd > 0
              || endcol2 == curwin->w_cursor.col)) {
        if (dir == FORWARD && c == NUL) {
          col++;
        }
        if (dir != FORWARD && c != NUL && curwin->w_cursor.coladd > 0) {
          curwin->w_cursor.col++;
        }
        if (c == TAB) {
          if (dir == BACKWARD && curwin->w_cursor.col)
            curwin->w_cursor.col--;
          if (dir == FORWARD && col - 1 == endcol2)
            curwin->w_cursor.col++;
        }
      }
      curwin->w_cursor.coladd = 0;
      bd.textcol = 0;
      for (i = 0; i < y_size; i++) {
        int spaces;
        char shortline;
  
        bd.startspaces = 0;
        bd.endspaces = 0;
        vcol = 0;
        delcount = 0;
  
        /* add a new line */
        if (curwin->w_cursor.lnum > curbuf->b_ml.ml_line_count) {
          if (ml_append(curbuf->b_ml.ml_line_count, (char_u *)"",
                        (colnr_T)1, false) == FAIL) {
            break;
          }
          nr_lines++;
        }
        /* get the old line and advance to the position to insert at */
        oldp = get_cursor_line_ptr();
        oldlen = STRLEN(oldp);
        for (ptr = oldp; vcol < col && *ptr; ) {
          /* Count a tab for what it's worth (if list mode not on) */
          incr = lbr_chartabsize_adv(oldp, &ptr, (colnr_T)vcol);
          vcol += incr;
        }
        bd.textcol = (colnr_T)(ptr - oldp);
  
        shortline = (vcol < col) || (vcol == col && !*ptr);
  
        if (vcol < col)       /* line too short, padd with spaces */
          bd.startspaces = col - vcol;
        else if (vcol > col) {
          bd.endspaces = vcol - col;
          bd.startspaces = incr - bd.endspaces;
          --bd.textcol;
          delcount = 1;
          bd.textcol -= utf_head_off(oldp, oldp + bd.textcol);
          if (oldp[bd.textcol] != TAB) {
            /* Only a Tab can be split into spaces.  Other
             * characters will have to be moved to after the
             * block, causing misalignment. */
            delcount = 0;
            bd.endspaces = 0;
          }
        }
  
        yanklen = (int)STRLEN(y_array[i]);
  
        // calculate number of spaces required to fill right side of block
        spaces = y_width + 1;
        for (long j = 0; j < yanklen; j++) {
          spaces -= lbr_chartabsize(NULL, &y_array[i][j], 0);
        }
        if (spaces < 0) {
          spaces = 0;
        }
  
        // insert the new text
        totlen = (size_t)(count * (yanklen + spaces)
                          + bd.startspaces + bd.endspaces);
        newp = (char_u *) xmalloc(totlen + oldlen + 1);
        // copy part up to cursor to new line
        ptr = newp;
        memmove(ptr, oldp, (size_t)bd.textcol);
        ptr += bd.textcol;
        // may insert some spaces before the new text
        memset(ptr, ' ', (size_t)bd.startspaces);
        ptr += bd.startspaces;
        // insert the new text
        for (long j = 0; j < count; j++) {
          memmove(ptr, y_array[i], (size_t)yanklen);
          ptr += yanklen;
  
          // insert block's trailing spaces only if there's text behind
          if ((j < count - 1 || !shortline) && spaces) {
            memset(ptr, ' ', (size_t)spaces);
            ptr += spaces;
          }
        }
        // may insert some spaces after the new text
        memset(ptr, ' ', (size_t)bd.endspaces);
        ptr += bd.endspaces;
        // move the text after the cursor to the end of the line.
        int columns = (int)oldlen - bd.textcol - delcount + 1;
        assert(columns >= 0);
        memmove(ptr, oldp + bd.textcol + delcount, (size_t)columns);
        ml_replace(curwin->w_cursor.lnum, newp, false);
        extmark_splice_cols(curbuf, (int)curwin->w_cursor.lnum-1, bd.textcol,
                            delcount, (int)totlen, kExtmarkUndo);
  
        ++curwin->w_cursor.lnum;
        if (i == 0)
          curwin->w_cursor.col += bd.startspaces;
      }
  
      changed_lines(lnum, 0, curwin->w_cursor.lnum, nr_lines, true);
  
      /* Set '[ mark. */
      curbuf->b_op_start = curwin->w_cursor;
      curbuf->b_op_start.lnum = lnum;
  
      /* adjust '] mark */
      curbuf->b_op_end.lnum = curwin->w_cursor.lnum - 1;
      curbuf->b_op_end.col = bd.textcol + (colnr_T)totlen - 1;
      curbuf->b_op_end.coladd = 0;
      if (flags & PUT_CURSEND) {
        colnr_T len;
  
        curwin->w_cursor = curbuf->b_op_end;
        curwin->w_cursor.col++;
  
        /* in Insert mode we might be after the NUL, correct for that */
        len = (colnr_T)STRLEN(get_cursor_line_ptr());
        if (curwin->w_cursor.col > len)
          curwin->w_cursor.col = len;
      } else
        curwin->w_cursor.lnum = lnum;
    } else {
      // Character or Line mode
      if (y_type == kMTCharWise) {
        // if type is kMTCharWise, FORWARD is the same as BACKWARD on the next
        // char
        if (dir == FORWARD && gchar_cursor() != NUL) {
          int bytelen = (*mb_ptr2len)(get_cursor_pos_ptr());
  
          // put it on the next of the multi-byte character.
          col += bytelen;
          if (yanklen) {
            curwin->w_cursor.col += bytelen;
            curbuf->b_op_end.col += bytelen;
          }
        }
        curbuf->b_op_start = curwin->w_cursor;
      }
      /*
       * Line mode: BACKWARD is the same as FORWARD on the previous line
       */
      else if (dir == BACKWARD)
        --lnum;
      new_cursor = curwin->w_cursor;
  
      // simple case: insert into one line at a time
      if (y_type == kMTCharWise && y_size == 1) {
        linenr_T end_lnum = 0;  // init for gcc
        linenr_T start_lnum = lnum;
  
        if (VIsual_active) {
          end_lnum = curbuf->b_visual.vi_end.lnum;
          if (end_lnum < curbuf->b_visual.vi_start.lnum) {
              end_lnum = curbuf->b_visual.vi_start.lnum;
          }
          if (end_lnum > start_lnum) {
            // "col" is valid for the first line, in following lines
            // the virtual column needs to be used.  Matters for
            // multi-byte characters.
            pos_T pos = {
              .lnum = lnum,
              .col = col,
              .coladd = 0,
            };
            getvcol(curwin, &pos, NULL, &vcol, NULL);
          }
        }
  
        do {
          totlen = (size_t)(count * yanklen);
          if (totlen > 0) {
            oldp = ml_get(lnum);
            if (lnum > start_lnum) {
              pos_T pos = {
                .lnum = lnum,
              };
              if (getvpos(&pos, vcol) == OK) {
                col = pos.col;
              } else {
                col = MAXCOL;
              }
            }
            if (VIsual_active && col > (int)STRLEN(oldp)) {
              lnum++;
              continue;
            }
            newp = (char_u *)xmalloc((size_t)(STRLEN(oldp) + totlen + 1));
            memmove(newp, oldp, (size_t)col);
            ptr = newp + col;
            for (i = 0; i < (size_t)count; i++) {
              memmove(ptr, y_array[0], (size_t)yanklen);
              ptr += yanklen;
            }
            STRMOVE(ptr, oldp + col);
            ml_replace(lnum, newp, false);
            // Place cursor on last putted char.
            if (lnum == curwin->w_cursor.lnum) {
              // make sure curwin->w_virtcol is updated
              changed_cline_bef_curs();
              curwin->w_cursor.col += (colnr_T)(totlen - 1);
            }
          }
          if (VIsual_active) {
            lnum++;
          }
        } while (VIsual_active && lnum <= end_lnum);
  
        if (VIsual_active) {  /* reset lnum to the last visual line */
          lnum--;
        }
  
        curbuf->b_op_end = curwin->w_cursor;
        /* For "CTRL-O p" in Insert mode, put cursor after last char */
        if (totlen && (restart_edit != 0 || (flags & PUT_CURSEND)))
          ++curwin->w_cursor.col;
        changed_bytes(lnum, col);
        extmark_splice_cols(curbuf, (int)lnum-1, col,
                            0, (int)totlen, kExtmarkUndo);
      } else {
        // Insert at least one line.  When y_type is kMTCharWise, break the first
        // line in two.
        for (cnt = 1; cnt <= count; cnt++) {
          i = 0;
          if (y_type == kMTCharWise) {
            // Split the current line in two at the insert position.
            // First insert y_array[size - 1] in front of second line.
            // Then append y_array[0] to first line.
            lnum = new_cursor.lnum;
            ptr = ml_get(lnum) + col;
            totlen = STRLEN(y_array[y_size - 1]);
            newp = (char_u *) xmalloc((size_t)(STRLEN(ptr) + totlen + 1));
            STRCPY(newp, y_array[y_size - 1]);
            STRCAT(newp, ptr);
            // insert second line
            ml_append(lnum, newp, (colnr_T)0, false);
            xfree(newp);
  
            oldp = ml_get(lnum);
            newp = (char_u *)xmalloc((size_t)col + (size_t)yanklen + 1);
            // copy first part of line
            memmove(newp, oldp, (size_t)col);
            // append to first line
            memmove(newp + col, y_array[0], (size_t)yanklen + 1);
            ml_replace(lnum, newp, false);
  
            curwin->w_cursor.lnum = lnum;
            i = 1;
          }
  
          for (; i < y_size; i++) {
            if ((y_type != kMTCharWise || i < y_size - 1)
                && ml_append(lnum, y_array[i], (colnr_T)0, false)
                == FAIL) {
              goto error;
            }
            lnum++;
            ++nr_lines;
            if (flags & PUT_FIXINDENT) {
              old_pos = curwin->w_cursor;
              curwin->w_cursor.lnum = lnum;
              ptr = ml_get(lnum);
              if (cnt == count && i == y_size - 1)
                lendiff = (int)STRLEN(ptr);
              if (*ptr == '#' && preprocs_left())
                indent = 0;                   /* Leave # lines at start */
              else if (*ptr == NUL)
                indent = 0;                   /* Ignore empty lines */
              else if (first_indent) {
                indent_diff = orig_indent - get_indent();
                indent = orig_indent;
                first_indent = FALSE;
              } else if ((indent = get_indent() + indent_diff) < 0)
                indent = 0;
              (void)set_indent(indent, SIN_NOMARK);
              curwin->w_cursor = old_pos;
              /* remember how many chars were removed */
              if (cnt == count && i == y_size - 1)
                lendiff -= (int)STRLEN(ml_get(lnum));
            }
          }
  
          bcount_t totsize = 0;
          int lastsize = 0;
          if (y_type == kMTCharWise
              || (y_type == kMTLineWise && flags & PUT_LINE_SPLIT)) {
            for (i = 0; i < y_size-1; i++) {
              totsize += (bcount_t)STRLEN(y_array[i]) + 1;
            }
            lastsize = (int)STRLEN(y_array[y_size-1]);
            totsize += lastsize;
          }
          if (y_type == kMTCharWise) {
            extmark_splice(curbuf, (int)new_cursor.lnum-1, col, 0, 0, 0,
                           (int)y_size-1, lastsize, totsize,
                           kExtmarkUndo);
          } else if (y_type == kMTLineWise && flags & PUT_LINE_SPLIT) {
            extmark_splice(curbuf, (int)new_cursor.lnum-1, col, 0, 0, 0,
                           (int)y_size+1, 0, totsize+1, kExtmarkUndo);
          }
        }
  
  error:
        // Adjust marks.
        if (y_type == kMTLineWise) {
          curbuf->b_op_start.col = 0;
          if (dir == FORWARD)
            curbuf->b_op_start.lnum++;
        }
        // Skip mark_adjust when adding lines after the last one, there
        // can't be marks there.
        if (curbuf->b_op_start.lnum + (y_type == kMTCharWise) - 1 + nr_lines
            < curbuf->b_ml.ml_line_count) {
          ExtmarkOp kind = (y_type == kMTLineWise && !(flags & PUT_LINE_SPLIT))
                           ? kExtmarkUndo : kExtmarkNOOP;
          mark_adjust(curbuf->b_op_start.lnum + (y_type == kMTCharWise),
                      (linenr_T)MAXLNUM, nr_lines, 0L, kind);
        }
  
        // note changed text for displaying and folding
        if (y_type == kMTCharWise) {
          changed_lines(curwin->w_cursor.lnum, col,
                        curwin->w_cursor.lnum + 1, nr_lines, true);
        } else {
          changed_lines(curbuf->b_op_start.lnum, 0,
                        curbuf->b_op_start.lnum, nr_lines, true);
        }
  
        /* put '] mark at last inserted character */
        curbuf->b_op_end.lnum = lnum;
        /* correct length for change in indent */
        col = (colnr_T)STRLEN(y_array[y_size - 1]) - lendiff;
        if (col > 1)
          curbuf->b_op_end.col = col - 1;
        else
          curbuf->b_op_end.col = 0;
  
        if (flags & PUT_CURSLINE) {
          /* ":put": put cursor on last inserted line */
          curwin->w_cursor.lnum = lnum;
          beginline(BL_WHITE | BL_FIX);
        } else if (flags & PUT_CURSEND) {
          // put cursor after inserted text
          if (y_type == kMTLineWise) {
            if (lnum >= curbuf->b_ml.ml_line_count) {
              curwin->w_cursor.lnum = curbuf->b_ml.ml_line_count;
            } else {
              curwin->w_cursor.lnum = lnum + 1;
            }
            curwin->w_cursor.col = 0;
          } else {
            curwin->w_cursor.lnum = lnum;
            curwin->w_cursor.col = col;
          }
        } else if (y_type == kMTLineWise) {
          // put cursor on first non-blank in first inserted line
          curwin->w_cursor.col = 0;
          if (dir == FORWARD)
            ++curwin->w_cursor.lnum;
          beginline(BL_WHITE | BL_FIX);
        } else            /* put cursor on first inserted character */
          curwin->w_cursor = new_cursor;
      }
    }
  
    msgmore(nr_lines);
    curwin->w_set_curswant = TRUE;
  
  end:
    if (allocated)
      xfree(insert_string);
    if (regname == '=')
      xfree(y_array);
  
    VIsual_active = FALSE;
  
    /* If the cursor is past the end of the line put it at the end. */
    adjust_cursor_eol();
  }  // NOLINT(readability/fn_size)
  
  /*
   * When the cursor is on the NUL past the end of the line and it should not be
   * there move it left.
   */
  void adjust_cursor_eol(void)
  {
    if (curwin->w_cursor.col > 0
        && gchar_cursor() == NUL
        && (ve_flags & VE_ONEMORE) == 0
        && !(restart_edit || (State & INSERT))) {
      /* Put the cursor on the last character in the line. */
      dec_cursor();
  
      if (ve_flags == VE_ALL) {
        colnr_T scol, ecol;
  
        /* Coladd is set to the width of the last character. */
        getvcol(curwin, &curwin->w_cursor, &scol, NULL, &ecol);
        curwin->w_cursor.coladd = ecol - scol + 1;
      }
    }
  }
  
  /*
   * Return TRUE if lines starting with '#' should be left aligned.
   */
  int preprocs_left(void)
  {
    return ((curbuf->b_p_si && !curbuf->b_p_cin)
            || (curbuf->b_p_cin && in_cinkeys('#', ' ', true)
                && curbuf->b_ind_hash_comment == 0));
  }
  
  /* Return the character name of the register with the given number */
  int get_register_name(int num)
  {
    if (num == -1)
      return '"';
    else if (num < 10)
      return num + '0';
    else if (num == DELETION_REGISTER)
      return '-';
    else if (num == STAR_REGISTER)
      return '*';
    else if (num == PLUS_REGISTER)
      return '+';
    else {
      return num + 'a' - 10;
    }
  }
  
  /*
   * ":dis" and ":registers": Display the contents of the yank registers.
   */
  void ex_display(exarg_T *eap)
  {
    char_u *p;
    yankreg_T *yb;
    int name;
    char_u *arg = eap->arg;
    int clen;
  
    if (arg != NULL && *arg == NUL)
      arg = NULL;
    int attr = HL_ATTR(HLF_8);
  
    /* Highlight title */
    MSG_PUTS_TITLE(_("\n--- Registers ---"));
    for (int i = -1; i < NUM_REGISTERS && !got_int; i++) {
      name = get_register_name(i);
  
      if (arg != NULL && vim_strchr(arg, name) == NULL) {
        continue;             /* did not ask for this register */
      }
  
  
      if (i == -1) {
        if (y_previous != NULL)
          yb = y_previous;
        else
          yb = &(y_regs[0]);
      } else
        yb = &(y_regs[i]);
  
      get_clipboard(name, &yb, true);
  
      if (name == mb_tolower(redir_reg)
          || (redir_reg == '"' && yb == y_previous)) {
        continue;  // do not list register being written to, the
                   // pointer can be freed
      }
  
      if (yb->y_array != NULL) {
        msg_putchar('\n');
        msg_putchar('"');
        msg_putchar(name);
        MSG_PUTS("   ");
  
        int n = Columns - 6;
        for (size_t j = 0; j < yb->y_size && n > 1; j++) {
          if (j) {
            MSG_PUTS_ATTR("^J", attr);
            n -= 2;
          }
          for (p = yb->y_array[j]; *p && (n -= ptr2cells(p)) >= 0; p++) {  // -V1019 NOLINT(whitespace/line_length)
            clen = (*mb_ptr2len)(p);
            msg_outtrans_len(p, clen);
            p += clen - 1;
          }
        }
        if (n > 1 && yb->y_type == kMTLineWise) {
          MSG_PUTS_ATTR("^J", attr);
        }
        ui_flush();  // show one line at a time
      }
      os_breakcheck();
    }
  
    /*
     * display last inserted text
     */
    if ((p = get_last_insert()) != NULL
        && (arg == NULL || vim_strchr(arg, '.') != NULL) && !got_int) {
      MSG_PUTS("\n\".   ");
      dis_msg(p, TRUE);
    }
  
    /*
     * display last command line
     */
    if (last_cmdline != NULL && (arg == NULL || vim_strchr(arg, ':') != NULL)
        && !got_int) {
      MSG_PUTS("\n\":   ");
      dis_msg(last_cmdline, FALSE);
    }
  
    /*
     * display current file name
     */
    if (curbuf->b_fname != NULL
        && (arg == NULL || vim_strchr(arg, '%') != NULL) && !got_int) {
      MSG_PUTS("\n\"%   ");
      dis_msg(curbuf->b_fname, FALSE);
    }
  
    /*
     * display alternate file name
     */
    if ((arg == NULL || vim_strchr(arg, '%') != NULL) && !got_int) {
      char_u      *fname;
      linenr_T dummy;
  
      if (buflist_name_nr(0, &fname, &dummy) != FAIL) {
        MSG_PUTS("\n\"#   ");
        dis_msg(fname, FALSE);
      }
    }
  
    /*
     * display last search pattern
     */
    if (last_search_pat() != NULL
        && (arg == NULL || vim_strchr(arg, '/') != NULL) && !got_int) {
      MSG_PUTS("\n\"/   ");
      dis_msg(last_search_pat(), FALSE);
    }
  
    /*
     * display last used expression
     */
    if (expr_line != NULL && (arg == NULL || vim_strchr(arg, '=') != NULL)
        && !got_int) {
      MSG_PUTS("\n\"=   ");
      dis_msg(expr_line, FALSE);
    }
  }
  
  /*
   * display a string for do_dis()
   * truncate at end of screen line
   */
  static void
  dis_msg(
      char_u *p,
      int skip_esc                       /* if TRUE, ignore trailing ESC */
  )
  {
    int n;
    int l;
  
    n = Columns - 6;
    while (*p != NUL
           && !(*p == ESC && skip_esc && *(p + 1) == NUL)
           && (n -= ptr2cells(p)) >= 0) {
      if ((l = utfc_ptr2len(p)) > 1) {
        msg_outtrans_len(p, l);
        p += l;
      } else
        msg_outtrans_len(p++, 1);
    }
    os_breakcheck();
  }
  
  /// If \p "process" is true and the line begins with a comment leader (possibly
  /// after some white space), return a pointer to the text after it.
  /// Put a boolean value indicating whether the line ends with an unclosed
  /// comment in "is_comment".
  ///
  /// @param line - line to be processed
  /// @param process - if false, will only check whether the line ends
  ///         with an unclosed comment,
  /// @param include_space - whether to skip space following the comment leader
  /// @param[out] is_comment - whether the current line ends with an unclosed
  ///  comment.
  char_u *skip_comment(
      char_u *line, bool process, bool include_space, bool *is_comment
  )
  {
    char_u *comment_flags = NULL;
    int lead_len;
    int leader_offset = get_last_leader_offset(line, &comment_flags);
  
    *is_comment = false;
    if (leader_offset != -1) {
      /* Let's check whether the line ends with an unclosed comment.
       * If the last comment leader has COM_END in flags, there's no comment.
       */
      while (*comment_flags) {
        if (*comment_flags == COM_END
            || *comment_flags == ':') {
          break;
        }
        comment_flags++;
      }
      if (*comment_flags != COM_END) {
        *is_comment = true;
      }
    }
  
    if (process == false) {
      return line;
    }
  
    lead_len = get_leader_len(line, &comment_flags, false, include_space);
  
    if (lead_len == 0)
      return line;
  
    /* Find:
     * - COM_END,
     * - colon,
     * whichever comes first.
     */
    while (*comment_flags) {
      if (*comment_flags == COM_END
          || *comment_flags == ':') {
        break;
      }
      ++comment_flags;
    }
  
    /* If we found a colon, it means that we are not processing a line
     * starting with a closing part of a three-part comment. That's good,
     * because we don't want to remove those as this would be annoying.
     */
    if (*comment_flags == ':' || *comment_flags == NUL) {
      line += lead_len;
    }
  
    return line;
  }
  
  // Join 'count' lines (minimal 2) at cursor position.
  // When "save_undo" is TRUE save lines for undo first.
  // Set "use_formatoptions" to FALSE when e.g. processing backspace and comment
  // leaders should not be removed.
  // When setmark is true, sets the '[ and '] mark, else, the caller is expected
  // to set those marks.
  //
  // return FAIL for failure, OK otherwise
  int do_join(size_t count,
              int insert_space,
              int save_undo,
              int use_formatoptions,
              bool setmark)
  {
    char_u      *curr = NULL;
    char_u      *curr_start = NULL;
    char_u      *cend;
    char_u      *newp;
    char_u      *spaces;          /* number of spaces inserted before a line */
    int endcurr1 = NUL;
    int endcurr2 = NUL;
    int currsize = 0;             /* size of the current line */
    int sumsize = 0;              /* size of the long new line */
    linenr_T t;
    colnr_T col = 0;
    int ret = OK;
    int         *comments = NULL;
    int remove_comments = (use_formatoptions == TRUE)
                          && has_format_option(FO_REMOVE_COMS);
    bool prev_was_comment = false;
    assert(count >= 1);
  
    if (save_undo && u_save(curwin->w_cursor.lnum - 1,
                            curwin->w_cursor.lnum + (linenr_T)count) == FAIL) {
      return FAIL;
    }
    // Allocate an array to store the number of spaces inserted before each
    // line.  We will use it to pre-compute the length of the new line and the
    // proper placement of each original line in the new one.
    spaces = xcalloc(count, 1);
    if (remove_comments) {
      comments = xcalloc(count, sizeof(*comments));
    }
  
    // Don't move anything, just compute the final line length
    // and setup the array of space strings lengths
    for (t = 0; t < (linenr_T)count; t++) {
      curr = curr_start = ml_get((linenr_T)(curwin->w_cursor.lnum + t));
      if (t == 0 && setmark) {
        // Set the '[ mark.
        curwin->w_buffer->b_op_start.lnum = curwin->w_cursor.lnum;
        curwin->w_buffer->b_op_start.col = (colnr_T)STRLEN(curr);
      }
      if (remove_comments) {
        // We don't want to remove the comment leader if the
        // previous line is not a comment.
        if (t > 0 && prev_was_comment) {
          char_u *new_curr = skip_comment(curr, true, insert_space,
                                          &prev_was_comment);
          comments[t] = (int)(new_curr - curr);
          curr = new_curr;
        } else {
          curr = skip_comment(curr, false, insert_space, &prev_was_comment);
        }
      }
  
      if (insert_space && t > 0) {
        curr = skipwhite(curr);
        if (*curr != NUL
            && *curr != ')'
            && sumsize != 0
            && endcurr1 != TAB
            && (!has_format_option(FO_MBYTE_JOIN)
                || (utf_ptr2char(curr) < 0x100 && endcurr1 < 0x100))
            && (!has_format_option(FO_MBYTE_JOIN2)
                || utf_ptr2char(curr) < 0x100 || endcurr1 < 0x100)
            ) {
          /* don't add a space if the line is ending in a space */
          if (endcurr1 == ' ')
            endcurr1 = endcurr2;
          else
            ++spaces[t];
          // Extra space when 'joinspaces' set and line ends in '.', '?', or '!'.
          if (p_js && (endcurr1 == '.' || endcurr1 == '?' || endcurr1 == '!')) {
            ++spaces[t];
          }
        }
      }
  
      if (t > 0 && curbuf_splice_pending == 0) {
        colnr_T removed = (int)(curr- curr_start);
        extmark_splice(curbuf, (int)curwin->w_cursor.lnum-1, sumsize,
                       1, removed, removed + 1,
                       0, spaces[t], spaces[t],
                       kExtmarkUndo);
      }
      currsize = (int)STRLEN(curr);
      sumsize += currsize + spaces[t];
      endcurr1 = endcurr2 = NUL;
      if (insert_space && currsize > 0) {
        cend = curr + currsize;
        MB_PTR_BACK(curr, cend);
        endcurr1 = utf_ptr2char(cend);
        if (cend > curr) {
          MB_PTR_BACK(curr, cend);
          endcurr2 = utf_ptr2char(cend);
        }
      }
      line_breakcheck();
      if (got_int) {
        ret = FAIL;
        goto theend;
      }
    }
  
    // store the column position before last line
    col = sumsize - currsize - spaces[count - 1];
  
    // allocate the space for the new line
    newp = (char_u *)xmalloc((size_t)sumsize + 1);
    cend = newp + sumsize;
    *cend = 0;
  
    /*
     * Move affected lines to the new long one.
     *
     * Move marks from each deleted line to the joined line, adjusting the
     * column.  This is not Vi compatible, but Vi deletes the marks, thus that
     * should not really be a problem.
     */
  
    curbuf_splice_pending++;
  
    for (t = (linenr_T)count - 1;; t--) {
      cend -= currsize;
      memmove(cend, curr, (size_t)currsize);
      if (spaces[t] > 0) {
        cend -= spaces[t];
        memset(cend, ' ', (size_t)(spaces[t]));
      }
  
      // If deleting more spaces than adding, the cursor moves no more than
      // what is added if it is inside these spaces.
      const int spaces_removed = (int)((curr - curr_start) - spaces[t]);
      linenr_T lnum = curwin->w_cursor.lnum + t;
      colnr_T mincol = (colnr_T)0;
      long lnum_amount = (linenr_T)-t;
      long col_amount = (long)(cend - newp - spaces_removed);
  
      mark_col_adjust(lnum, mincol, lnum_amount, col_amount, spaces_removed);
  
      if (t == 0) {
        break;
      }
  
      curr = curr_start = ml_get((linenr_T)(curwin->w_cursor.lnum + t - 1));
      if (remove_comments)
        curr += comments[t - 1];
      if (insert_space && t > 1)
        curr = skipwhite(curr);
      currsize = (int)STRLEN(curr);
    }
  
    ml_replace(curwin->w_cursor.lnum, newp, false);
  
    if (setmark) {
      // Set the '] mark.
      curwin->w_buffer->b_op_end.lnum = curwin->w_cursor.lnum;
      curwin->w_buffer->b_op_end.col = sumsize;
    }
  
    /* Only report the change in the first line here, del_lines() will report
     * the deleted line. */
    changed_lines(curwin->w_cursor.lnum, currsize,
                  curwin->w_cursor.lnum + 1, 0L, true);
  
    /*
     * Delete following lines. To do this we move the cursor there
     * briefly, and then move it back. After del_lines() the cursor may
     * have moved up (last line deleted), so the current lnum is kept in t.
     */
    t = curwin->w_cursor.lnum;
    curwin->w_cursor.lnum++;
    del_lines((long)count - 1, false);
    curwin->w_cursor.lnum = t;
    curbuf_splice_pending--;
  
    /*
     * Set the cursor column:
     * Vi compatible: use the column of the first join
     * vim:	      use the column of the last join
     */
    curwin->w_cursor.col =
      (vim_strchr(p_cpo, CPO_JOINCOL) != NULL ? currsize : col);
    check_cursor_col();
  
    curwin->w_cursor.coladd = 0;
    curwin->w_set_curswant = TRUE;
  
  theend:
    xfree(spaces);
    if (remove_comments)
      xfree(comments);
    return ret;
  }
  
  /*
   * Return TRUE if the two comment leaders given are the same.  "lnum" is
   * the first line.  White-space is ignored.  Note that the whole of
   * 'leader1' must match 'leader2_len' characters from 'leader2' -- webb
   */
  static int same_leader(linenr_T lnum, int leader1_len, char_u *leader1_flags, int leader2_len, char_u *leader2_flags)
  {
    int idx1 = 0, idx2 = 0;
    char_u  *p;
    char_u  *line1;
    char_u  *line2;
  
    if (leader1_len == 0)
      return leader2_len == 0;
  
    /*
     * If first leader has 'f' flag, the lines can be joined only if the
     * second line does not have a leader.
     * If first leader has 'e' flag, the lines can never be joined.
     * If fist leader has 's' flag, the lines can only be joined if there is
     * some text after it and the second line has the 'm' flag.
     */
    if (leader1_flags != NULL) {
      for (p = leader1_flags; *p && *p != ':'; ++p) {
        if (*p == COM_FIRST)
          return leader2_len == 0;
        if (*p == COM_END)
          return FALSE;
        if (*p == COM_START) {
          if (*(ml_get(lnum) + leader1_len) == NUL)
            return FALSE;
          if (leader2_flags == NULL || leader2_len == 0)
            return FALSE;
          for (p = leader2_flags; *p && *p != ':'; ++p)
            if (*p == COM_MIDDLE)
              return TRUE;
          return FALSE;
        }
      }
    }
  
    /*
     * Get current line and next line, compare the leaders.
     * The first line has to be saved, only one line can be locked at a time.
     */
    line1 = vim_strsave(ml_get(lnum));
    for (idx1 = 0; ascii_iswhite(line1[idx1]); ++idx1)
      ;
    line2 = ml_get(lnum + 1);
    for (idx2 = 0; idx2 < leader2_len; ++idx2) {
      if (!ascii_iswhite(line2[idx2])) {
        if (line1[idx1++] != line2[idx2])
          break;
      } else
        while (ascii_iswhite(line1[idx1]))
          ++idx1;
    }
    xfree(line1);
  
    return idx2 == leader2_len && idx1 == leader1_len;
  }
  
  /*
   * Implementation of the format operator 'gq'.
   */
  void
  op_format(
      oparg_T *oap,
      int keep_cursor                        /* keep cursor on same text char */
  )
  {
    long old_line_count = curbuf->b_ml.ml_line_count;
  
    /* Place the cursor where the "gq" or "gw" command was given, so that "u"
     * can put it back there. */
    curwin->w_cursor = oap->cursor_start;
  
    if (u_save((linenr_T)(oap->start.lnum - 1),
            (linenr_T)(oap->end.lnum + 1)) == FAIL)
      return;
    curwin->w_cursor = oap->start;
  
    if (oap->is_VIsual)
      /* When there is no change: need to remove the Visual selection */
      redraw_curbuf_later(INVERTED);
  
    /* Set '[ mark at the start of the formatted area */
    curbuf->b_op_start = oap->start;
  
    /* For "gw" remember the cursor position and put it back below (adjusted
     * for joined and split lines). */
    if (keep_cursor)
      saved_cursor = oap->cursor_start;
  
    format_lines(oap->line_count, keep_cursor);
  
    /*
     * Leave the cursor at the first non-blank of the last formatted line.
     * If the cursor was moved one line back (e.g. with "Q}") go to the next
     * line, so "." will do the next lines.
     */
    if (oap->end_adjusted && curwin->w_cursor.lnum < curbuf->b_ml.ml_line_count)
      ++curwin->w_cursor.lnum;
    beginline(BL_WHITE | BL_FIX);
    old_line_count = curbuf->b_ml.ml_line_count - old_line_count;
    msgmore(old_line_count);
  
    /* put '] mark on the end of the formatted area */
    curbuf->b_op_end = curwin->w_cursor;
  
    if (keep_cursor) {
      curwin->w_cursor = saved_cursor;
      saved_cursor.lnum = 0;
    }
  
    if (oap->is_VIsual) {
      FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
        if (wp->w_old_cursor_lnum != 0) {
          /* When lines have been inserted or deleted, adjust the end of
           * the Visual area to be redrawn. */
          if (wp->w_old_cursor_lnum > wp->w_old_visual_lnum) {
            wp->w_old_cursor_lnum += old_line_count;
          } else {
            wp->w_old_visual_lnum += old_line_count;
          }
        }
      }
    }
  }
  
  /*
   * Implementation of the format operator 'gq' for when using 'formatexpr'.
   */
  void op_formatexpr(oparg_T *oap)
  {
    if (oap->is_VIsual)
      /* When there is no change: need to remove the Visual selection */
      redraw_curbuf_later(INVERTED);
  
    if (fex_format(oap->start.lnum, oap->line_count, NUL) != 0)
      /* As documented: when 'formatexpr' returns non-zero fall back to
       * internal formatting. */
      op_format(oap, FALSE);
  }
  
  int
  fex_format(
      linenr_T lnum,
      long count,
      int c                  /* character to be inserted */
  )
  {
    int use_sandbox = was_set_insecurely((char_u *)"formatexpr",
        OPT_LOCAL);
    int r;
    char_u *fex;
  
    /*
     * Set v:lnum to the first line number and v:count to the number of lines.
     * Set v:char to the character to be inserted (can be NUL).
     */
    set_vim_var_nr(VV_LNUM, (varnumber_T)lnum);
    set_vim_var_nr(VV_COUNT, (varnumber_T)count);
    set_vim_var_char(c);
  
    // Make a copy, the option could be changed while calling it.
    fex = vim_strsave(curbuf->b_p_fex);
    // Evaluate the function.
    if (use_sandbox) {
      sandbox++;
    }
    r = (int)eval_to_number(fex);
    if (use_sandbox) {
      sandbox--;
    }
  
    set_vim_var_string(VV_CHAR, NULL, -1);
    xfree(fex);
  
    return r;
  }
  
  /*
   * Format "line_count" lines, starting at the cursor position.
   * When "line_count" is negative, format until the end of the paragraph.
   * Lines after the cursor line are saved for undo, caller must have saved the
   * first line.
   */
  void
  format_lines(
      linenr_T line_count,
      int avoid_fex                          /* don't use 'formatexpr' */
  )
  {
    int max_len;
    int is_not_par;                       /* current line not part of parag. */
    int next_is_not_par;                  /* next line not part of paragraph */
    int is_end_par;                       /* at end of paragraph */
    int prev_is_end_par = FALSE;          /* prev. line not part of parag. */
    int next_is_start_par = FALSE;
    int leader_len = 0;                   /* leader len of current line */
    int next_leader_len;                  /* leader len of next line */
    char_u      *leader_flags = NULL;     /* flags for leader of current line */
    char_u      *next_leader_flags;       /* flags for leader of next line */
    int do_comments;                      /* format comments */
    int do_comments_list = 0;             /* format comments with 'n' or '2' */
    int advance = TRUE;
    int second_indent = -1;               /* indent for second line (comment
                                           * aware) */
    int do_second_indent;
    int do_number_indent;
    int do_trail_white;
    int first_par_line = TRUE;
    int smd_save;
    long count;
    int need_set_indent = TRUE;           /* set indent of next paragraph */
    int force_format = FALSE;
    int old_State = State;
  
    /* length of a line to force formatting: 3 * 'tw' */
    max_len = comp_textwidth(TRUE) * 3;
  
    /* check for 'q', '2' and '1' in 'formatoptions' */
    do_comments = has_format_option(FO_Q_COMS);
    do_second_indent = has_format_option(FO_Q_SECOND);
    do_number_indent = has_format_option(FO_Q_NUMBER);
    do_trail_white = has_format_option(FO_WHITE_PAR);
  
    /*
     * Get info about the previous and current line.
     */
    if (curwin->w_cursor.lnum > 1)
      is_not_par = fmt_check_par(curwin->w_cursor.lnum - 1
          , &leader_len, &leader_flags, do_comments
          );
    else
      is_not_par = TRUE;
    next_is_not_par = fmt_check_par(curwin->w_cursor.lnum
        , &next_leader_len, &next_leader_flags, do_comments
        );
    is_end_par = (is_not_par || next_is_not_par);
    if (!is_end_par && do_trail_white)
      is_end_par = !ends_in_white(curwin->w_cursor.lnum - 1);
  
    curwin->w_cursor.lnum--;
    for (count = line_count; count != 0 && !got_int; --count) {
      /*
       * Advance to next paragraph.
       */
      if (advance) {
        curwin->w_cursor.lnum++;
        prev_is_end_par = is_end_par;
        is_not_par = next_is_not_par;
        leader_len = next_leader_len;
        leader_flags = next_leader_flags;
      }
  
      /*
       * The last line to be formatted.
       */
      if (count == 1 || curwin->w_cursor.lnum == curbuf->b_ml.ml_line_count) {
        next_is_not_par = TRUE;
        next_leader_len = 0;
        next_leader_flags = NULL;
      } else {
        next_is_not_par = fmt_check_par(curwin->w_cursor.lnum + 1
            , &next_leader_len, &next_leader_flags, do_comments
            );
        if (do_number_indent)
          next_is_start_par =
            (get_number_indent(curwin->w_cursor.lnum + 1) > 0);
      }
      advance = TRUE;
      is_end_par = (is_not_par || next_is_not_par || next_is_start_par);
      if (!is_end_par && do_trail_white)
        is_end_par = !ends_in_white(curwin->w_cursor.lnum);
  
      /*
       * Skip lines that are not in a paragraph.
       */
      if (is_not_par) {
        if (line_count < 0)
          break;
      } else {
        /*
         * For the first line of a paragraph, check indent of second line.
         * Don't do this for comments and empty lines.
         */
        if (first_par_line
            && (do_second_indent || do_number_indent)
            && prev_is_end_par
            && curwin->w_cursor.lnum < curbuf->b_ml.ml_line_count) {
          if (do_second_indent && !LINEEMPTY(curwin->w_cursor.lnum + 1)) {
            if (leader_len == 0 && next_leader_len == 0) {
              /* no comment found */
              second_indent =
                get_indent_lnum(curwin->w_cursor.lnum + 1);
            } else {
              second_indent = next_leader_len;
              do_comments_list = 1;
            }
          } else if (do_number_indent) {
            if (leader_len == 0 && next_leader_len == 0) {
              /* no comment found */
              second_indent =
                get_number_indent(curwin->w_cursor.lnum);
            } else {
              /* get_number_indent() is now "comment aware"... */
              second_indent =
                get_number_indent(curwin->w_cursor.lnum);
              do_comments_list = 1;
            }
          }
        }
  
        /*
         * When the comment leader changes, it's the end of the paragraph.
         */
        if (curwin->w_cursor.lnum >= curbuf->b_ml.ml_line_count
            || !same_leader(curwin->w_cursor.lnum,
                leader_len, leader_flags,
                next_leader_len, next_leader_flags)
            )
          is_end_par = TRUE;
  
        /*
         * If we have got to the end of a paragraph, or the line is
         * getting long, format it.
         */
        if (is_end_par || force_format) {
          if (need_set_indent)
            /* replace indent in first line with minimal number of
             * tabs and spaces, according to current options */
            (void)set_indent(get_indent(), SIN_CHANGED);
  
          /* put cursor on last non-space */
          State = NORMAL;         /* don't go past end-of-line */
          coladvance((colnr_T)MAXCOL);
          while (curwin->w_cursor.col && ascii_isspace(gchar_cursor()))
            dec_cursor();
  
          /* do the formatting, without 'showmode' */
          State = INSERT;         /* for open_line() */
          smd_save = p_smd;
          p_smd = FALSE;
          insertchar(NUL, INSCHAR_FORMAT
              + (do_comments ? INSCHAR_DO_COM : 0)
              + (do_comments && do_comments_list
                 ? INSCHAR_COM_LIST : 0)
              + (avoid_fex ? INSCHAR_NO_FEX : 0), second_indent);
          State = old_State;
          p_smd = smd_save;
          second_indent = -1;
          /* at end of par.: need to set indent of next par. */
          need_set_indent = is_end_par;
          if (is_end_par) {
            /* When called with a negative line count, break at the
             * end of the paragraph. */
            if (line_count < 0)
              break;
            first_par_line = TRUE;
          }
          force_format = FALSE;
        }
  
        /*
         * When still in same paragraph, join the lines together.  But
         * first delete the leader from the second line.
         */
        if (!is_end_par) {
          advance = FALSE;
          curwin->w_cursor.lnum++;
          curwin->w_cursor.col = 0;
          if (line_count < 0 && u_save_cursor() == FAIL)
            break;
          if (next_leader_len > 0) {
            (void)del_bytes(next_leader_len, false, false);
            mark_col_adjust(curwin->w_cursor.lnum, (colnr_T)0, 0L,
                            (long)-next_leader_len, 0);
          } else if (second_indent > 0) {   // the "leader" for FO_Q_SECOND
            int indent = (int)getwhitecols_curline();
  
            if (indent > 0) {
              (void)del_bytes(indent, false, false);
              mark_col_adjust(curwin->w_cursor.lnum,
                              (colnr_T)0, 0L, (long)-indent, 0);
            }
          }
          curwin->w_cursor.lnum--;
          if (do_join(2, TRUE, FALSE, FALSE, false) == FAIL) {
            beep_flush();
            break;
          }
          first_par_line = FALSE;
          /* If the line is getting long, format it next time */
          if (STRLEN(get_cursor_line_ptr()) > (size_t)max_len)
            force_format = TRUE;
          else
            force_format = FALSE;
        }
      }
      line_breakcheck();
    }
  }
  
  /*
   * Return TRUE if line "lnum" ends in a white character.
   */
  static int ends_in_white(linenr_T lnum)
  {
    char_u      *s = ml_get(lnum);
    size_t l;
  
    if (*s == NUL)
      return FALSE;
    l = STRLEN(s) - 1;
    return ascii_iswhite(s[l]);
  }
  
  /*
   * Blank lines, and lines containing only the comment leader, are left
   * untouched by the formatting.  The function returns TRUE in this
   * case.  It also returns TRUE when a line starts with the end of a comment
   * ('e' in comment flags), so that this line is skipped, and not joined to the
   * previous line.  A new paragraph starts after a blank line, or when the
   * comment leader changes -- webb.
   */
  static int fmt_check_par(linenr_T lnum, int *leader_len, char_u **leader_flags, int do_comments)
  {
    char_u      *flags = NULL;        /* init for GCC */
    char_u      *ptr;
  
    ptr = ml_get(lnum);
    if (do_comments)
      *leader_len = get_leader_len(ptr, leader_flags, FALSE, TRUE);
    else
      *leader_len = 0;
  
    if (*leader_len > 0) {
      /*
       * Search for 'e' flag in comment leader flags.
       */
      flags = *leader_flags;
      while (*flags && *flags != ':' && *flags != COM_END)
        ++flags;
    }
  
    return *skipwhite(ptr + *leader_len) == NUL
           || (*leader_len > 0 && *flags == COM_END)
           || startPS(lnum, NUL, FALSE);
  }
  
  /*
   * Return TRUE when a paragraph starts in line "lnum".  Return FALSE when the
   * previous line is in the same paragraph.  Used for auto-formatting.
   */
  int paragraph_start(linenr_T lnum)
  {
    char_u *p;
    int leader_len = 0;                   /* leader len of current line */
    char_u *leader_flags = NULL;          /* flags for leader of current line */
    int next_leader_len = 0;              /* leader len of next line */
    char_u *next_leader_flags = NULL;     /* flags for leader of next line */
    int do_comments;                      /* format comments */
  
    if (lnum <= 1)
      return TRUE;                /* start of the file */
  
    p = ml_get(lnum - 1);
    if (*p == NUL)
      return TRUE;                /* after empty line */
  
    do_comments = has_format_option(FO_Q_COMS);
    if (fmt_check_par(lnum - 1, &leader_len, &leader_flags, do_comments)) {
      return true;  // after non-paragraph line
    }
  
    if (fmt_check_par(lnum, &next_leader_len, &next_leader_flags, do_comments)) {
      return true;  // "lnum" is not a paragraph line
    }
  
    if (has_format_option(FO_WHITE_PAR) && !ends_in_white(lnum - 1))
      return TRUE;                /* missing trailing space in previous line. */
  
    if (has_format_option(FO_Q_NUMBER) && (get_number_indent(lnum) > 0))
      return TRUE;                /* numbered item starts in "lnum". */
  
    if (!same_leader(lnum - 1, leader_len, leader_flags,
            next_leader_len, next_leader_flags))
      return TRUE;                /* change of comment leader. */
  
    return FALSE;
  }
  
  /*
   * prepare a few things for block mode yank/delete/tilde
   *
   * for delete:
   * - textlen includes the first/last char to be (partly) deleted
   * - start/endspaces is the number of columns that are taken by the
   *   first/last deleted char minus the number of columns that have to be
   *   deleted.
   * for yank and tilde:
   * - textlen includes the first/last char to be wholly yanked
   * - start/endspaces is the number of columns of the first/last yanked char
   *   that are to be yanked.
   */
  static void block_prep(oparg_T *oap, struct block_def *bdp, linenr_T lnum,
                         bool is_del)
  {
    int incr = 0;
    char_u      *pend;
    char_u      *pstart;
    char_u      *line;
    char_u      *prev_pstart;
    char_u      *prev_pend;
    const int lbr_saved = curwin->w_p_lbr;
  
    // Avoid a problem with unwanted linebreaks in block mode.
    curwin->w_p_lbr = false;
    bdp->startspaces = 0;
    bdp->endspaces = 0;
    bdp->textlen = 0;
    bdp->start_vcol = 0;
    bdp->end_vcol = 0;
    bdp->is_short = false;
    bdp->is_oneChar = false;
    bdp->pre_whitesp = 0;
    bdp->pre_whitesp_c = 0;
    bdp->end_char_vcols = 0;
    bdp->start_char_vcols = 0;
  
    line = ml_get(lnum);
    pstart = line;
    prev_pstart = line;
    while (bdp->start_vcol < oap->start_vcol && *pstart) {
      /* Count a tab for what it's worth (if list mode not on) */
      incr = lbr_chartabsize(line, pstart, (colnr_T)bdp->start_vcol);
      bdp->start_vcol += incr;
      if (ascii_iswhite(*pstart)) {
        bdp->pre_whitesp += incr;
        bdp->pre_whitesp_c++;
      } else {
        bdp->pre_whitesp = 0;
        bdp->pre_whitesp_c = 0;
      }
      prev_pstart = pstart;
      MB_PTR_ADV(pstart);
    }
    bdp->start_char_vcols = incr;
    if (bdp->start_vcol < oap->start_vcol) {      /* line too short */
      bdp->end_vcol = bdp->start_vcol;
      bdp->is_short = true;
      if (!is_del || oap->op_type == OP_APPEND) {
        bdp->endspaces = oap->end_vcol - oap->start_vcol + 1;
      }
    } else {
      /* notice: this converts partly selected Multibyte characters to
       * spaces, too. */
      bdp->startspaces = bdp->start_vcol - oap->start_vcol;
      if (is_del && bdp->startspaces)
        bdp->startspaces = bdp->start_char_vcols - bdp->startspaces;
      pend = pstart;
      bdp->end_vcol = bdp->start_vcol;
      if (bdp->end_vcol > oap->end_vcol) {  // it's all in one character
        bdp->is_oneChar = true;
        if (oap->op_type == OP_INSERT) {
          bdp->endspaces = bdp->start_char_vcols - bdp->startspaces;
        } else if (oap->op_type == OP_APPEND) {
          bdp->startspaces += oap->end_vcol - oap->start_vcol + 1;
          bdp->endspaces = bdp->start_char_vcols - bdp->startspaces;
        } else {
          bdp->startspaces = oap->end_vcol - oap->start_vcol + 1;
          if (is_del && oap->op_type != OP_LSHIFT) {
            /* just putting the sum of those two into
             * bdp->startspaces doesn't work for Visual replace,
             * so we have to split the tab in two */
            bdp->startspaces = bdp->start_char_vcols
                               - (bdp->start_vcol - oap->start_vcol);
            bdp->endspaces = bdp->end_vcol - oap->end_vcol - 1;
          }
        }
      } else {
        prev_pend = pend;
        while (bdp->end_vcol <= oap->end_vcol && *pend != NUL) {
          /* Count a tab for what it's worth (if list mode not on) */
          prev_pend = pend;
          incr = lbr_chartabsize_adv(line, &pend, (colnr_T)bdp->end_vcol);
          bdp->end_vcol += incr;
        }
        if (bdp->end_vcol <= oap->end_vcol
            && (!is_del
                || oap->op_type == OP_APPEND
                || oap->op_type == OP_REPLACE)) {  // line too short
          bdp->is_short = true;
          // Alternative: include spaces to fill up the block.
          // Disadvantage: can lead to trailing spaces when the line is
          // short where the text is put
          // if (!is_del || oap->op_type == OP_APPEND)
          if (oap->op_type == OP_APPEND || virtual_op) {
            bdp->endspaces = oap->end_vcol - bdp->end_vcol
                             + oap->inclusive;
          }
        } else if (bdp->end_vcol > oap->end_vcol) {
          bdp->endspaces = bdp->end_vcol - oap->end_vcol - 1;
          if (!is_del && bdp->endspaces) {
            bdp->endspaces = incr - bdp->endspaces;
            if (pend != pstart)
              pend = prev_pend;
          }
        }
      }
      bdp->end_char_vcols = incr;
      if (is_del && bdp->startspaces)
        pstart = prev_pstart;
      bdp->textlen = (int)(pend - pstart);
    }
    bdp->textcol = (colnr_T) (pstart - line);
    bdp->textstart = pstart;
    curwin->w_p_lbr = lbr_saved;
  }
  
  /// Handle the add/subtract operator.
  ///
  /// @param[in]  oap      Arguments of operator.
  /// @param[in]  Prenum1  Amount of addition or subtraction.
  /// @param[in]  g_cmd    Prefixed with `g`.
  void op_addsub(oparg_T *oap, linenr_T Prenum1, bool g_cmd)
  {
    pos_T pos;
    struct block_def bd;
    ssize_t change_cnt = 0;
    linenr_T amount = Prenum1;
  
    if (!VIsual_active) {
      pos = curwin->w_cursor;
      if (u_save_cursor() == FAIL) {
        return;
      }
      change_cnt = do_addsub(oap->op_type, &pos, 0, amount);
      if (change_cnt) {
        changed_lines(pos.lnum, 0, pos.lnum + 1, 0L, true);
      }
    } else {
      int one_change;
      int length;
      pos_T startpos;
  
      if (u_save((linenr_T)(oap->start.lnum - 1),
                 (linenr_T)(oap->end.lnum + 1)) == FAIL) {
        return;
      }
  
      pos = oap->start;
      for (; pos.lnum <= oap->end.lnum; pos.lnum++) {
        if (oap->motion_type == kMTBlockWise) {
          // Visual block mode
          block_prep(oap, &bd, pos.lnum, false);
          pos.col = bd.textcol;
          length = bd.textlen;
        } else if (oap->motion_type == kMTLineWise) {
          curwin->w_cursor.col = 0;
          pos.col = 0;
          length = (colnr_T)STRLEN(ml_get(pos.lnum));
        } else {
          // oap->motion_type == kMTCharWise
          if (pos.lnum == oap->start.lnum && !oap->inclusive) {
            dec(&(oap->end));
          }
          length = (colnr_T)STRLEN(ml_get(pos.lnum));
          pos.col = 0;
          if (pos.lnum == oap->start.lnum) {
            pos.col += oap->start.col;
            length -= oap->start.col;
          }
          if (pos.lnum == oap->end.lnum) {
            length = (int)STRLEN(ml_get(oap->end.lnum));
            if (oap->end.col >= length) {
              oap->end.col = length - 1;
            }
            length = oap->end.col - pos.col + 1;
          }
        }
        one_change = do_addsub(oap->op_type, &pos, length, amount);
        if (one_change) {
          // Remember the start position of the first change.
          if (change_cnt == 0) {
            startpos = curbuf->b_op_start;
          }
          change_cnt++;
        }
  
        if (g_cmd && one_change) {
          amount += Prenum1;
        }
      }
      if (change_cnt) {
        changed_lines(oap->start.lnum, 0, oap->end.lnum + 1, 0L, true);
      }
  
      if (!change_cnt && oap->is_VIsual) {
        // No change: need to remove the Visual selection
        redraw_curbuf_later(INVERTED);
      }
  
      // Set '[ mark if something changed. Keep the last end
      // position from do_addsub().
      if (change_cnt > 0) {
        curbuf->b_op_start = startpos;
      }
  
      if (change_cnt > p_report) {
        if (change_cnt == 1) {
          MSG(_("1 line changed"));
        } else {
          smsg((char *)_("%" PRId64 " lines changed"), (int64_t)change_cnt);
        }
      }
    }
  }
  
  /// Add or subtract from a number in a line.
  ///
  /// @param op_type OP_NR_ADD or OP_NR_SUB.
  /// @param pos     Cursor position.
  /// @param length  Target number length.
  /// @param Prenum1 Amount of addition or subtraction.
  ///
  /// @return true if some character was changed.
  int do_addsub(int op_type, pos_T *pos, int length, linenr_T Prenum1)
  {
    int col;
    char_u      *buf1 = NULL;
    char_u buf2[NUMBUFLEN];
    int pre;  // 'X' or 'x': hex; '0': octal; 'B' or 'b': bin
    static bool hexupper = false;  // 0xABC
    uvarnumber_T n;
    uvarnumber_T oldn;
    char_u      *ptr;
    int c;
    int todel;
    bool dohex;
    bool dooct;
    bool dobin;
    bool doalp;
    int firstdigit;
    bool subtract;
    bool negative = false;
    bool was_positive = true;
    bool visual = VIsual_active;
    bool did_change = false;
    pos_T save_cursor = curwin->w_cursor;
    int maxlen = 0;
    pos_T startpos;
    pos_T endpos;
    colnr_T save_coladd = 0;
  
    dohex = (vim_strchr(curbuf->b_p_nf, 'x') != NULL);    // "heX"
    dooct = (vim_strchr(curbuf->b_p_nf, 'o') != NULL);    // "Octal"
    dobin = (vim_strchr(curbuf->b_p_nf, 'b') != NULL);    // "Bin"
    doalp = (vim_strchr(curbuf->b_p_nf, 'p') != NULL);    // "alPha"
  
    if (virtual_active()) {
      save_coladd = pos->coladd;
      pos->coladd = 0;
    }
  
    curwin->w_cursor = *pos;
    ptr = ml_get(pos->lnum);
    col = pos->col;
  
    if (*ptr == NUL || col + !!save_coladd >= (int)STRLEN(ptr)) {
      goto theend;
    }
  
    // First check if we are on a hexadecimal number, after the "0x".
    if (!VIsual_active) {
      if (dobin) {
        while (col > 0 && ascii_isbdigit(ptr[col])) {
          col--;
          col -= utf_head_off(ptr, ptr + col);
        }
      }
  
      if (dohex) {
        while (col > 0 && ascii_isxdigit(ptr[col])) {
          col--;
          col -= utf_head_off(ptr, ptr + col);
        }
      }
      if (dobin
          && dohex
          && !((col > 0
                && (ptr[col] == 'X' || ptr[col] == 'x')
                && ptr[col - 1] == '0'
                && !utf_head_off(ptr, ptr + col - 1)
                && ascii_isxdigit(ptr[col + 1])))) {
          // In case of binary/hexadecimal pattern overlap match, rescan
  
          col = curwin->w_cursor.col;
  
          while (col > 0 && ascii_isdigit(ptr[col])) {
            col--;
            col -= utf_head_off(ptr, ptr + col);
          }
      }
  
      if ((dohex
           && col > 0
           && (ptr[col] == 'X' || ptr[col] == 'x')
           && ptr[col - 1] == '0'
           && !utf_head_off(ptr, ptr + col - 1)
           && ascii_isxdigit(ptr[col + 1]))
          || (dobin
              && col > 0
              && (ptr[col] == 'B' || ptr[col] == 'b')
              && ptr[col - 1] == '0'
              && !utf_head_off(ptr, ptr + col - 1)
              && ascii_isbdigit(ptr[col + 1]))) {
        // Found hexadecimal or binary number, move to its start.
          col--;
          col -= utf_head_off(ptr, ptr + col);
      } else {
        // Search forward and then backward to find the start of number.
        col = pos->col;
  
        while (ptr[col] != NUL
               && !ascii_isdigit(ptr[col])
               && !(doalp && ASCII_ISALPHA(ptr[col]))) {
          col++;
        }
  
        while (col > 0
               && ascii_isdigit(ptr[col - 1])
               && !(doalp && ASCII_ISALPHA(ptr[col]))) {
          col--;
        }
      }
    }
  
    if (visual) {
      while (ptr[col] != NUL && length > 0 && !ascii_isdigit(ptr[col])
             && !(doalp && ASCII_ISALPHA(ptr[col]))) {
        int mb_len = utfc_ptr2len(ptr + col);
  
        col += mb_len;
        length -= mb_len;
      }
  
      if (length == 0) {
        goto theend;
      }
  
      if (col > pos->col && ptr[col - 1] == '-'
          && !utf_head_off(ptr, ptr + col - 1)) {
        negative = true;
        was_positive = false;
      }
    }
  
    // If a number was found, and saving for undo works, replace the number.
    firstdigit = ptr[col];
    if (!ascii_isdigit(firstdigit) && !(doalp && ASCII_ISALPHA(firstdigit))) {
      beep_flush();
      goto theend;
    }
  
    if (doalp && ASCII_ISALPHA(firstdigit)) {
      // decrement or increment alphabetic character
      if (op_type == OP_NR_SUB) {
        if (CharOrd(firstdigit) < Prenum1) {
          if (isupper(firstdigit)) {
            firstdigit = 'A';
          } else {
            firstdigit = 'a';
          }
        } else {
          firstdigit -= (int)Prenum1;
        }
      } else {
        if (26 - CharOrd(firstdigit) - 1 < Prenum1) {
          if (isupper(firstdigit)) {
            firstdigit = 'Z';
          } else {
            firstdigit = 'z';
          }
        } else {
          firstdigit += (int)Prenum1;
        }
      }
      curwin->w_cursor.col = col;
      startpos = curwin->w_cursor;
      did_change = true;
      (void)del_char(false);
      ins_char(firstdigit);
      endpos = curwin->w_cursor;
      curwin->w_cursor.col = col;
    } else {
      if (col > 0 && ptr[col - 1] == '-'
          && !utf_head_off(ptr, ptr + col - 1) && !visual) {
        // negative number
        col--;
        negative = true;
      }
  
      // get the number value (unsigned)
      if (visual && VIsual_mode != 'V') {
        maxlen = (curbuf->b_visual.vi_curswant == MAXCOL
                  ? (int)STRLEN(ptr) - col
                  : length);
      }
  
      vim_str2nr(ptr + col, &pre, &length,
                 0 + (dobin ? STR2NR_BIN : 0)
                 + (dooct ? STR2NR_OCT : 0)
                 + (dohex ? STR2NR_HEX : 0),
                 NULL, &n, maxlen);
  
      // ignore leading '-' for hex, octal and bin numbers
      if (pre && negative) {
        col++;
        length--;
        negative = false;
      }
  
      // add or subtract
      subtract = false;
      if (op_type == OP_NR_SUB) {
        subtract ^= true;
      }
      if (negative) {
        subtract ^= true;
      }
  
      oldn = n;
  
      n = subtract ? n - (uvarnumber_T)Prenum1
                   : n + (uvarnumber_T)Prenum1;
  
      // handle wraparound for decimal numbers
      if (!pre) {
        if (subtract) {
          if (n > oldn) {
            n = 1 + (n ^ (uvarnumber_T)-1);
            negative ^= true;
          }
        } else {
          // add
          if (n < oldn) {
            n = (n ^ (uvarnumber_T)-1);
            negative ^= true;
          }
        }
        if (n == 0) {
          negative = false;
        }
      }
  
      if (visual && !was_positive && !negative && col > 0) {
        // need to remove the '-'
        col--;
        length++;
      }
  
      // Delete the old number.
      curwin->w_cursor.col = col;
      startpos = curwin->w_cursor;
      did_change = true;
      todel = length;
      c = gchar_cursor();
  
      // Don't include the '-' in the length, only the length of the part
      // after it is kept the same.
      if (c == '-') {
        length--;
      }
      while (todel-- > 0) {
        if (c < 0x100 && isalpha(c)) {
          if (isupper(c)) {
            hexupper = true;
          } else {
            hexupper = false;
          }
        }
        // del_char() will mark line needing displaying
        (void)del_char(false);
        c = gchar_cursor();
      }
  
      // Prepare the leading characters in buf1[].
      // When there are many leading zeros it could be very long.
      // Allocate a bit too much.
      buf1 = xmalloc((size_t)length + NUMBUFLEN);
      ptr = buf1;
      if (negative && (!visual || was_positive)) {
        *ptr++ = '-';
      }
      if (pre) {
        *ptr++ = '0';
        length--;
      }
      if (pre == 'b' || pre == 'B' || pre == 'x' || pre == 'X') {
        *ptr++ = (char_u)pre;
        length--;
      }
  
      // Put the number characters in buf2[].
      if (pre == 'b' || pre == 'B') {
        size_t bits = 0;
        size_t i = 0;
  
        // leading zeros
        for (bits = 8 * sizeof(n); bits > 0; bits--) {
            if ((n >> (bits - 1)) & 0x1) {
              break;
            }
        }
  
        while (bits > 0) {
            buf2[i++] = ((n >> --bits) & 0x1) ? '1' : '0';
        }
  
        buf2[i] = '\0';
  
      } else if (pre == 0) {
        vim_snprintf((char *)buf2, ARRAY_SIZE(buf2), "%" PRIu64, (uint64_t)n);
      } else if (pre == '0') {
        vim_snprintf((char *)buf2, ARRAY_SIZE(buf2), "%" PRIo64, (uint64_t)n);
      } else if (hexupper) {
        vim_snprintf((char *)buf2, ARRAY_SIZE(buf2), "%" PRIX64, (uint64_t)n);
      } else {
        vim_snprintf((char *)buf2, ARRAY_SIZE(buf2), "%" PRIx64, (uint64_t)n);
      }
      length -= (int)STRLEN(buf2);
  
      // Adjust number of zeros to the new number of digits, so the
      // total length of the number remains the same.
      // Don't do this when
      // the result may look like an octal number.
      if (firstdigit == '0' && !(dooct && pre == 0)) {
        while (length-- > 0) {
          *ptr++ = '0';
        }
      }
      *ptr = NUL;
      STRCAT(buf1, buf2);
      ins_str(buf1);              // insert the new number
      endpos = curwin->w_cursor;
      if (curwin->w_cursor.col) {
        curwin->w_cursor.col--;
      }
    }
  
    // set the '[ and '] marks
    curbuf->b_op_start = startpos;
    curbuf->b_op_end = endpos;
    if (curbuf->b_op_end.col > 0) {
      curbuf->b_op_end.col--;
    }
  
  theend:
    xfree(buf1);
    if (visual) {
      curwin->w_cursor = save_cursor;
    } else if (did_change) {
      curwin->w_set_curswant = true;
    } else if (virtual_active()) {
      curwin->w_cursor.coladd = save_coladd;
    }
  
    return did_change;
  }
  
  /*
   * Return the type of a register.
   * Used for getregtype()
   * Returns kMTUnknown for error.
   */
  MotionType get_reg_type(int regname, colnr_T *reg_width)
  {
    switch (regname) {
      case '%':     // file name
      case '#':     // alternate file name
      case '=':     // expression
      case ':':     // last command line
      case '/':     // last search-pattern
      case '.':     // last inserted text
      case Ctrl_F:  // Filename under cursor
      case Ctrl_P:  // Path under cursor, expand via "path"
      case Ctrl_W:  // word under cursor
      case Ctrl_A:  // WORD (mnemonic All) under cursor
      case '_':     // black hole: always empty
        return kMTCharWise;
    }
  
    if (regname != NUL && !valid_yank_reg(regname, false)) {
      return kMTUnknown;
    }
  
    yankreg_T *reg = get_yank_register(regname, YREG_PASTE);
  
    if (reg->y_array != NULL) {
      if (reg_width != NULL && reg->y_type == kMTBlockWise) {
        *reg_width = reg->y_width;
      }
      return reg->y_type;
    }
    return kMTUnknown;
  }
  
  /// Format the register type as a string.
  ///
  /// @param reg_type The register type.
  /// @param reg_width The width, only used if "reg_type" is kMTBlockWise.
  /// @param[out] buf Buffer to store formatted string. The allocated size should
  ///                 be at least NUMBUFLEN+2 to always fit the value.
  /// @param buf_len The allocated size of the buffer.
  void format_reg_type(MotionType reg_type, colnr_T reg_width,
                       char *buf, size_t buf_len)
    FUNC_ATTR_NONNULL_ALL
  {
    assert(buf_len > 1);
    switch (reg_type) {
      case kMTLineWise:
        buf[0] = 'V';
        buf[1] = NUL;
        break;
      case kMTCharWise:
        buf[0] = 'v';
        buf[1] = NUL;
        break;
      case kMTBlockWise:
        snprintf(buf, buf_len, CTRL_V_STR "%" PRIdCOLNR, reg_width + 1);
        break;
      case kMTUnknown:
        buf[0] = NUL;
        break;
    }
  }
  
  
  /// When `flags` has `kGRegList` return a list with text `s`.
  /// Otherwise just return `s`.
  ///
  /// Returns a void * for use in get_reg_contents().
  static void *get_reg_wrap_one_line(char_u *s, int flags)
  {
    if (!(flags & kGRegList)) {
      return s;
    }
    list_T *const list = tv_list_alloc(1);
    tv_list_append_allocated_string(list, (char *)s);
    return list;
  }
  
  /// Gets the contents of a register.
  /// @remark Used for `@r` in expressions and for `getreg()`.
  ///
  /// @param regname  The register.
  /// @param flags    see @ref GRegFlags
  ///
  /// @returns The contents of the register as an allocated string.
  /// @returns A linked list when `flags` contains @ref kGRegList.
  /// @returns NULL for error.
  void *get_reg_contents(int regname, int flags)
  {
    // Don't allow using an expression register inside an expression.
    if (regname == '=') {
      if (flags & kGRegNoExpr) {
        return NULL;
      }
      if (flags & kGRegExprSrc) {
        return get_reg_wrap_one_line(get_expr_line_src(), flags);
      }
      return get_reg_wrap_one_line(get_expr_line(), flags);
    }
  
    if (regname == '@')       /* "@@" is used for unnamed register */
      regname = '"';
  
    /* check for valid regname */
    if (regname != NUL && !valid_yank_reg(regname, false))
      return NULL;
  
    char_u *retval;
    bool allocated;
    if (get_spec_reg(regname, &retval, &allocated, false)) {
      if (retval == NULL) {
        return NULL;
      }
      if (allocated) {
        return get_reg_wrap_one_line(retval, flags);
      }
      return get_reg_wrap_one_line(vim_strsave(retval), flags);
    }
  
    yankreg_T *reg = get_yank_register(regname, YREG_PASTE);
    if (reg->y_array == NULL)
      return NULL;
  
    if (flags & kGRegList) {
      list_T *const list = tv_list_alloc((ptrdiff_t)reg->y_size);
      for (size_t i = 0; i < reg->y_size; i++) {
        tv_list_append_string(list, (const char *)reg->y_array[i], -1);
      }
  
      return list;
    }
  
    /*
     * Compute length of resulting string.
     */
    size_t len = 0;
    for (size_t i = 0; i < reg->y_size; i++) {
      len += STRLEN(reg->y_array[i]);
      /*
       * Insert a newline between lines and after last line if
       * y_type is kMTLineWise.
       */
      if (reg->y_type == kMTLineWise || i < reg->y_size - 1) {
        len++;
      }
    }
  
    retval = xmalloc(len + 1);
  
    /*
     * Copy the lines of the yank register into the string.
     */
    len = 0;
    for (size_t i = 0; i < reg->y_size; i++) {
      STRCPY(retval + len, reg->y_array[i]);
      len += STRLEN(retval + len);
  
      /*
       * Insert a NL between lines and after the last line if y_type is
       * kMTLineWise.
       */
      if (reg->y_type == kMTLineWise || i < reg->y_size - 1) {
        retval[len++] = '\n';
      }
    }
    retval[len] = NUL;
  
    return retval;
  }
  
  static yankreg_T *init_write_reg(int name, yankreg_T **old_y_previous, bool must_append)
  {
    if (!valid_yank_reg(name, true)) {  // check for valid reg name
      emsg_invreg(name);
      return NULL;
    }
  
    // Don't want to change the current (unnamed) register.
    *old_y_previous = y_previous;
  
    yankreg_T *reg = get_yank_register(name, YREG_YANK);
    if (!is_append_register(name) && !must_append) {
        free_register(reg);
    }
    return reg;
  }
  
  static void finish_write_reg(int name, yankreg_T *reg, yankreg_T *old_y_previous)
  {
    // Send text of clipboard register to the clipboard.
    set_clipboard(name, reg);
  
    // ':let @" = "val"' should change the meaning of the "" register
    if (name != '"') {
      y_previous = old_y_previous;
    }
  }
  
  /// write_reg_contents - store `str` in register `name`
  ///
  /// @see write_reg_contents_ex
  void write_reg_contents(int name, const char_u *str, ssize_t len,
                          int must_append)
  {
    write_reg_contents_ex(name, str, len, must_append, kMTUnknown, 0L);
  }
  
  void write_reg_contents_lst(int name, char_u **strings,
                              bool must_append, MotionType yank_type,
                              colnr_T block_len)
  {
    if (name == '/' || name == '=') {
      char_u  *s = strings[0];
      if (strings[0] == NULL) {
        s = (char_u *)"";
      } else if (strings[1] != NULL) {
        EMSG(_("E883: search pattern and expression register may not "
               "contain two or more lines"));
        return;
      }
      write_reg_contents_ex(name, s, -1, must_append, yank_type, block_len);
      return;
    }
  
    // black hole: nothing to do
    if (name == '_') {
      return;
    }
  
    yankreg_T  *old_y_previous, *reg;
    if (!(reg = init_write_reg(name, &old_y_previous, must_append))) {
      return;
    }
  
    str_to_reg(reg, yank_type, (char_u *)strings, STRLEN((char_u *)strings),
               block_len, true);
    finish_write_reg(name, reg, old_y_previous);
  }
  
  /// write_reg_contents_ex - store `str` in register `name`
  ///
  /// If `str` ends in '\n' or '\r', use linewise, otherwise use charwise.
  ///
  /// @warning when `name` is '/', `len` and `must_append` are ignored. This
  ///          means that `str` MUST be NUL-terminated.
  ///
  /// @param name The name of the register
  /// @param str The contents to write
  /// @param len If >= 0, write `len` bytes of `str`. Otherwise, write
  ///               `strlen(str)` bytes. If `len` is larger than the
  ///               allocated size of `src`, the behaviour is undefined.
  /// @param must_append If true, append the contents of `str` to the current
  ///                    contents of the register. Note that regardless of
  ///                    `must_append`, this function will append when `name`
  ///                    is an uppercase letter.
  /// @param yank_type The motion type (kMTUnknown to auto detect)
  /// @param block_len width of visual block
  void write_reg_contents_ex(int name,
                             const char_u *str,
                             ssize_t len,
                             bool must_append,
                             MotionType yank_type,
                             colnr_T block_len)
  {
    if (len < 0) {
      len = (ssize_t) STRLEN(str);
    }
  
    /* Special case: '/' search pattern */
    if (name == '/') {
      set_last_search_pat(str, RE_SEARCH, TRUE, TRUE);
      return;
    }
  
    if (name == '#') {
      buf_T *buf;
  
      if (ascii_isdigit(*str)) {
        int num = atoi((char *)str);
  
        buf = buflist_findnr(num);
        if (buf == NULL) {
          EMSGN(_(e_nobufnr), (long)num);
        }
      } else {
        buf = buflist_findnr(buflist_findpat(str, str + STRLEN(str),
                                             true, false, false));
      }
      if (buf == NULL) {
        return;
      }
      curwin->w_alt_fnum = buf->b_fnum;
      return;
    }
  
    if (name == '=') {
      size_t offset = 0;
      size_t totlen = (size_t) len;
  
      if (must_append && expr_line) {
        // append has been specified and expr_line already exists, so we'll
        // append the new string to expr_line.
        size_t exprlen = STRLEN(expr_line);
  
        totlen += exprlen;
        offset = exprlen;
      }
  
      // modify the global expr_line, extend/shrink it if necessary (realloc).
      // Copy the input string into the adjusted memory at the specified
      // offset.
      expr_line = xrealloc(expr_line, totlen + 1);
      memcpy(expr_line + offset, str, (size_t)len);
      expr_line[totlen] = NUL;
  
      return;
    }
  
    if (name == '_') {        // black hole: nothing to do
      return;
    }
  
    yankreg_T  *old_y_previous, *reg;
    if (!(reg = init_write_reg(name, &old_y_previous, must_append))) {
      return;
    }
    str_to_reg(reg, yank_type, str, (size_t)len, block_len, false);
    finish_write_reg(name, reg, old_y_previous);
  }
  
  /// str_to_reg - Put a string into a register.
  ///
  /// When the register is not empty, the string is appended.
  ///
  /// @param y_ptr pointer to yank register
  /// @param yank_type The motion type (kMTUnknown to auto detect)
  /// @param str string or list of strings to put in register
  /// @param len length of the string (Ignored when str_list=true.)
  /// @param blocklen width of visual block, or -1 for "I don't know."
  /// @param str_list True if str is `char_u **`.
  static void str_to_reg(yankreg_T *y_ptr, MotionType yank_type,
                         const char_u *str, size_t len, colnr_T blocklen,
                         bool str_list)
    FUNC_ATTR_NONNULL_ALL
  {
    if (y_ptr->y_array == NULL) {  // NULL means empty register
      y_ptr->y_size = 0;
    }
  
    if (yank_type == kMTUnknown) {
      yank_type = ((str_list
                    || (len > 0 && (str[len - 1] == NL || str[len - 1] == CAR)))
                   ? kMTLineWise : kMTCharWise);
    }
  
    size_t newlines = 0;
    bool extraline = false;  // extra line at the end
    bool append = false;     // append to last line in register
  
    // Count the number of lines within the string
    if (str_list) {
      for (char_u **ss = (char_u **) str; *ss != NULL; ++ss) {
        newlines++;
      }
    } else {
      newlines = memcnt(str, '\n', len);
      if (yank_type == kMTCharWise || len == 0 || str[len - 1] != '\n') {
        extraline = 1;
        ++newlines;         // count extra newline at the end
      }
      if (y_ptr->y_size > 0 && y_ptr->y_type == kMTCharWise) {
        append = true;
        --newlines;         // uncount newline when appending first line
      }
    }
  
  
    // Grow the register array to hold the pointers to the new lines.
    char_u **pp = xrealloc(y_ptr->y_array,
                           (y_ptr->y_size + newlines) * sizeof(char_u *));
    y_ptr->y_array = pp;
  
    size_t lnum = y_ptr->y_size;  // The current line number.
  
    // If called with `blocklen < 0`, we have to update the yank reg's width.
    size_t maxlen = 0;
  
    // Find the end of each line and save it into the array.
    if (str_list) {
      for (char_u **ss = (char_u **) str; *ss != NULL; ++ss, ++lnum) {
        size_t ss_len = STRLEN(*ss);
        pp[lnum] = xmemdupz(*ss, ss_len);
        if (ss_len > maxlen) {
          maxlen = ss_len;
        }
      }
    } else {
      size_t line_len;
      for (const char_u *start = str, *end = str + len;
           start < end + extraline;
           start += line_len + 1, lnum++) {
        assert(end - start >= 0);
        line_len = (size_t)((char_u *)xmemscan(start, '\n',
                                               (size_t)(end - start)) - start);
        if (line_len > maxlen) {
          maxlen = line_len;
        }
  
        // When appending, copy the previous line and free it after.
        size_t extra = append ? STRLEN(pp[--lnum]) : 0;
        char_u *s = xmallocz(line_len + extra);
        memcpy(s, pp[lnum], extra);
        memcpy(s + extra, start, line_len);
        size_t s_len = extra + line_len;
  
        if (append) {
          xfree(pp[lnum]);
          append = false;  // only first line is appended
        }
        pp[lnum] = s;
  
        // Convert NULs to '\n' to prevent truncation.
        memchrsub(pp[lnum], NUL, '\n', s_len);
      }
    }
    y_ptr->y_type = yank_type;
    y_ptr->y_size = lnum;
    set_yreg_additional_data(y_ptr, NULL);
    y_ptr->timestamp = os_time();
    if (yank_type == kMTBlockWise) {
      y_ptr->y_width = (blocklen == -1 ? (colnr_T) maxlen - 1 : blocklen);
    } else {
      y_ptr->y_width = 0;
    }
  }
  
  void clear_oparg(oparg_T *oap)
  {
    memset(oap, 0, sizeof(oparg_T));
  }
  
  
  /*
   *  Count the number of bytes, characters and "words" in a line.
   *
   *  "Words" are counted by looking for boundaries between non-space and
   *  space characters.  (it seems to produce results that match 'wc'.)
   *
   *  Return value is byte count; word count for the line is added to "*wc".
   *  Char count is added to "*cc".
   *
   *  The function will only examine the first "limit" characters in the
   *  line, stopping if it encounters an end-of-line (NUL byte).  In that
   *  case, eol_size will be added to the character count to account for
   *  the size of the EOL character.
   */
  static varnumber_T line_count_info(char_u *line, varnumber_T *wc,
                                     varnumber_T *cc, varnumber_T limit,
                                     int eol_size)
  {
    varnumber_T i;
    varnumber_T words = 0;
    varnumber_T chars = 0;
    int is_word = 0;
  
    for (i = 0; i < limit && line[i] != NUL; ) {
      if (is_word) {
        if (ascii_isspace(line[i])) {
          words++;
          is_word = 0;
        }
      } else if (!ascii_isspace(line[i]))
        is_word = 1;
      ++chars;
      i += (*mb_ptr2len)(line + i);
    }
  
    if (is_word)
      words++;
    *wc += words;
  
    /* Add eol_size if the end of line was reached before hitting limit. */
    if (i < limit && line[i] == NUL) {
      i += eol_size;
      chars += eol_size;
    }
    *cc += chars;
    return i;
  }
  
  /// Give some info about the position of the cursor (for "g CTRL-G").
  /// In Visual mode, give some info about the selected region.  (In this case,
  /// the *_count_cursor variables store running totals for the selection.)
  /// When "dict" is not NULL store the info there instead of showing it.
  void cursor_pos_info(dict_T *dict)
  {
    char_u      *p;
    char_u buf1[50];
    char_u buf2[40];
    linenr_T lnum;
    varnumber_T byte_count = 0;
    varnumber_T bom_count = 0;
    varnumber_T byte_count_cursor = 0;
    varnumber_T char_count = 0;
    varnumber_T char_count_cursor = 0;
    varnumber_T word_count = 0;
    varnumber_T word_count_cursor = 0;
    int eol_size;
    varnumber_T last_check = 100000L;
    long line_count_selected = 0;
    pos_T min_pos, max_pos;
    oparg_T oparg;
    struct block_def bd;
    const int l_VIsual_active = VIsual_active;
    const int l_VIsual_mode = VIsual_mode;
  
    // Compute the length of the file in characters.
    if (curbuf->b_ml.ml_flags & ML_EMPTY) {
      if (dict == NULL) {
        MSG(_(no_lines_msg));
        return;
      }
    } else {
      if (get_fileformat(curbuf) == EOL_DOS)
        eol_size = 2;
      else
        eol_size = 1;
  
      if (l_VIsual_active) {
        if (lt(VIsual, curwin->w_cursor)) {
          min_pos = VIsual;
          max_pos = curwin->w_cursor;
        } else {
          min_pos = curwin->w_cursor;
          max_pos = VIsual;
        }
        if (*p_sel == 'e' && max_pos.col > 0)
          --max_pos.col;
  
        if (l_VIsual_mode == Ctrl_V) {
          char_u * saved_sbr = p_sbr;
  
          /* Make 'sbr' empty for a moment to get the correct size. */
          p_sbr = empty_option;
          oparg.is_VIsual = true;
          oparg.motion_type = kMTBlockWise;
          oparg.op_type = OP_NOP;
          getvcols(curwin, &min_pos, &max_pos,
              &oparg.start_vcol, &oparg.end_vcol);
          p_sbr = saved_sbr;
          if (curwin->w_curswant == MAXCOL)
            oparg.end_vcol = MAXCOL;
          /* Swap the start, end vcol if needed */
          if (oparg.end_vcol < oparg.start_vcol) {
            oparg.end_vcol += oparg.start_vcol;
            oparg.start_vcol = oparg.end_vcol - oparg.start_vcol;
            oparg.end_vcol -= oparg.start_vcol;
          }
        }
        line_count_selected = max_pos.lnum - min_pos.lnum + 1;
      }
  
      for (lnum = 1; lnum <= curbuf->b_ml.ml_line_count; ++lnum) {
        /* Check for a CTRL-C every 100000 characters. */
        if (byte_count > last_check) {
          os_breakcheck();
          if (got_int)
            return;
          last_check = byte_count + 100000L;
        }
  
        /* Do extra processing for VIsual mode. */
        if (l_VIsual_active
            && lnum >= min_pos.lnum && lnum <= max_pos.lnum) {
          char_u      *s = NULL;
          long len = 0L;
  
          switch (l_VIsual_mode) {
          case Ctrl_V:
            virtual_op = virtual_active();
            block_prep(&oparg, &bd, lnum, false);
            virtual_op = kNone;
            s = bd.textstart;
            len = (long)bd.textlen;
            break;
          case 'V':
            s = ml_get(lnum);
            len = MAXCOL;
            break;
          case 'v':
          {
            colnr_T start_col = (lnum == min_pos.lnum)
                                ? min_pos.col : 0;
            colnr_T end_col = (lnum == max_pos.lnum)
                              ? max_pos.col - start_col + 1 : MAXCOL;
  
            s = ml_get(lnum) + start_col;
            len = end_col;
          }
          break;
          }
          if (s != NULL) {
            byte_count_cursor += line_count_info(s, &word_count_cursor,
                &char_count_cursor, len, eol_size);
            if (lnum == curbuf->b_ml.ml_line_count
                && !curbuf->b_p_eol
                && (curbuf->b_p_bin || !curbuf->b_p_fixeol)
                && (long)STRLEN(s) < len)
              byte_count_cursor -= eol_size;
          }
        } else {
          /* In non-visual mode, check for the line the cursor is on */
          if (lnum == curwin->w_cursor.lnum) {
            word_count_cursor += word_count;
            char_count_cursor += char_count;
            byte_count_cursor = byte_count
              + line_count_info(ml_get(lnum), &word_count_cursor,
                                &char_count_cursor,
                                (varnumber_T)curwin->w_cursor.col + 1,
                                eol_size);
          }
        }
        // Add to the running totals
        byte_count += line_count_info(ml_get(lnum), &word_count, &char_count,
                                      (varnumber_T)MAXCOL, eol_size);
      }
  
      // Correction for when last line doesn't have an EOL.
      if (!curbuf->b_p_eol && (curbuf->b_p_bin || !curbuf->b_p_fixeol)) {
        byte_count -= eol_size;
      }
  
      if (dict == NULL) {
        if (l_VIsual_active) {
          if (l_VIsual_mode == Ctrl_V && curwin->w_curswant < MAXCOL) {
            getvcols(curwin, &min_pos, &max_pos, &min_pos.col, &max_pos.col);
            int64_t cols;
            STRICT_SUB(oparg.end_vcol + 1, oparg.start_vcol, &cols, int64_t);
            vim_snprintf((char *)buf1, sizeof(buf1), _("%" PRId64 " Cols; "),
                         cols);
          } else {
            buf1[0] = NUL;
          }
  
          if (char_count_cursor == byte_count_cursor
              && char_count == byte_count) {
            vim_snprintf((char *)IObuff, IOSIZE,
                         _("Selected %s%" PRId64 " of %" PRId64 " Lines;"
                           " %" PRId64 " of %" PRId64 " Words;"
                           " %" PRId64 " of %" PRId64 " Bytes"),
                         buf1, (int64_t)line_count_selected,
                         (int64_t)curbuf->b_ml.ml_line_count,
                         (int64_t)word_count_cursor, (int64_t)word_count,
                         (int64_t)byte_count_cursor, (int64_t)byte_count);
          } else {
            vim_snprintf((char *)IObuff, IOSIZE,
                         _("Selected %s%" PRId64 " of %" PRId64 " Lines;"
                           " %" PRId64 " of %" PRId64 " Words;"
                           " %" PRId64 " of %" PRId64 " Chars;"
                           " %" PRId64 " of %" PRId64 " Bytes"),
                         buf1, (int64_t)line_count_selected,
                         (int64_t)curbuf->b_ml.ml_line_count,
                         (int64_t)word_count_cursor, (int64_t)word_count,
                         (int64_t)char_count_cursor, (int64_t)char_count,
                         (int64_t)byte_count_cursor, (int64_t)byte_count);
          }
        } else {
          p = get_cursor_line_ptr();
          validate_virtcol();
          col_print(buf1, sizeof(buf1), (int)curwin->w_cursor.col + 1,
                    (int)curwin->w_virtcol + 1);
          col_print(buf2, sizeof(buf2), (int)STRLEN(p), linetabsize(p));
  
          if (char_count_cursor == byte_count_cursor
              && char_count == byte_count) {
            vim_snprintf((char *)IObuff, IOSIZE,
                         _("Col %s of %s; Line %" PRId64 " of %" PRId64 ";"
                           " Word %" PRId64 " of %" PRId64 ";"
                           " Byte %" PRId64 " of %" PRId64 ""),
                         (char *)buf1, (char *)buf2,
                         (int64_t)curwin->w_cursor.lnum,
                         (int64_t)curbuf->b_ml.ml_line_count,
                         (int64_t)word_count_cursor, (int64_t)word_count,
                         (int64_t)byte_count_cursor, (int64_t)byte_count);
          } else {
            vim_snprintf((char *)IObuff, IOSIZE,
                         _("Col %s of %s; Line %" PRId64 " of %" PRId64 ";"
                           " Word %" PRId64 " of %" PRId64 ";"
                           " Char %" PRId64 " of %" PRId64 ";"
                           " Byte %" PRId64 " of %" PRId64 ""),
                         (char *)buf1, (char *)buf2,
                         (int64_t)curwin->w_cursor.lnum,
                         (int64_t)curbuf->b_ml.ml_line_count,
                         (int64_t)word_count_cursor, (int64_t)word_count,
                         (int64_t)char_count_cursor, (int64_t)char_count,
                         (int64_t)byte_count_cursor, (int64_t)byte_count);
          }
        }
      }
  
      bom_count = bomb_size();
      if (dict == NULL && bom_count > 0) {
        const size_t len = STRLEN(IObuff);
        vim_snprintf((char *)IObuff + len, IOSIZE - len,
                     _("(+%" PRId64 " for BOM)"), (int64_t)bom_count);
      }
      if (dict == NULL) {
        // Don't shorten this message, the user asked for it.
        p = p_shm;
        p_shm = (char_u *)"";
        msg(IObuff);
        p_shm = p;
      }
    }
  
    if (dict != NULL) {
      // Don't shorten this message, the user asked for it.
      tv_dict_add_nr(dict, S_LEN("words"), (varnumber_T)word_count);
      tv_dict_add_nr(dict, S_LEN("chars"), (varnumber_T)char_count);
      tv_dict_add_nr(dict, S_LEN("bytes"), (varnumber_T)(byte_count + bom_count));
  
      STATIC_ASSERT(sizeof("visual") == sizeof("cursor"),
                    "key_len argument in tv_dict_add_nr is wrong");
      tv_dict_add_nr(dict, l_VIsual_active ? "visual_bytes" : "cursor_bytes",
                     sizeof("visual_bytes") - 1, (varnumber_T)byte_count_cursor);
      tv_dict_add_nr(dict, l_VIsual_active ? "visual_chars" : "cursor_chars",
                     sizeof("visual_chars") - 1, (varnumber_T)char_count_cursor);
      tv_dict_add_nr(dict, l_VIsual_active ? "visual_words" : "cursor_words",
                     sizeof("visual_words") - 1, (varnumber_T)word_count_cursor);
    }
  }
  
  /// Check if the default register (used in an unnamed paste) should be a
  /// clipboard register. This happens when `clipboard=unnamed[plus]` is set
  /// and a provider is available.
  ///
  /// @returns the name of of a clipboard register that should be used, or `NUL` if none.
  int get_default_register_name(void)
  {
    int name = NUL;
    adjust_clipboard_name(&name, true, false);
    return name;
  }
  
  /// Determine if register `*name` should be used as a clipboard.
  /// In an unnamed operation, `*name` is `NUL` and will be adjusted to */+ if
  /// `clipboard=unnamed[plus]` is set.
  ///
  /// @param name The name of register, or `NUL` if unnamed.
  /// @param quiet Suppress error messages
  /// @param writing if we're setting the contents of the clipboard
  ///
  /// @returns the yankreg that should be written into, or `NULL`
  /// if the register isn't a clipboard or provider isn't available.
  static yankreg_T *adjust_clipboard_name(int *name, bool quiet, bool writing)
  {
  #define MSG_NO_CLIP "clipboard: No provider. " \
    "Try \":checkhealth\" or \":h clipboard\"."
  
    yankreg_T *target = NULL;
    bool explicit_cb_reg = (*name == '*' || *name == '+');
    bool implicit_cb_reg = (*name == NUL) && (cb_flags & CB_UNNAMEDMASK);
    if (!explicit_cb_reg && !implicit_cb_reg) {
      goto end;
    }
  
    if (!eval_has_provider("clipboard")) {
      if (batch_change_count == 1 && !quiet
          && (!clipboard_didwarn || (explicit_cb_reg && !redirecting()))) {
        clipboard_didwarn = true;
        // Do NOT error (emsg()) here--if it interrupts :redir we get into
        // a weird state, stuck in "redirect mode".
        msg((char_u *)MSG_NO_CLIP);
      }
      // ... else, be silent (don't flood during :while, :redir, etc.).
      goto end;
    }
  
    if (explicit_cb_reg) {
      target = &y_regs[*name == '*' ? STAR_REGISTER : PLUS_REGISTER];
      if (writing && (cb_flags & (*name == '*' ? CB_UNNAMED : CB_UNNAMEDPLUS))) {
        clipboard_needs_update = false;
      }
      goto end;
    } else {  // unnamed register: "implicit" clipboard
      if (writing && clipboard_delay_update) {
        // For "set" (copy), defer the clipboard call.
        clipboard_needs_update = true;
        goto end;
      } else if (!writing && clipboard_needs_update) {
        // For "get" (paste), use the internal value.
        goto end;
      }
  
      if (cb_flags & CB_UNNAMEDPLUS) {
        *name = (cb_flags & CB_UNNAMED && writing) ? '"': '+';
        target = &y_regs[PLUS_REGISTER];
      } else {
        *name = '*';
        target = &y_regs[STAR_REGISTER];
      }
      goto end;
    }
  
  end:
    return target;
  }
  
  /// @param[out] reg Expected to be empty
  bool prepare_yankreg_from_object(yankreg_T *reg, String regtype, size_t lines)
  {
    char type = regtype.data ? regtype.data[0] : NUL;
  
    switch (type) {
    case 0:
      reg->y_type = kMTUnknown;
      break;
    case 'v': case 'c':
      reg->y_type = kMTCharWise;
      break;
    case 'V': case 'l':
      reg->y_type = kMTLineWise;
      break;
    case 'b': case Ctrl_V:
      reg->y_type = kMTBlockWise;
      break;
    default:
      return false;
    }
  
    reg->y_width = 0;
    if (regtype.size > 1) {
      if (reg->y_type != kMTBlockWise) {
        return false;
      }
  
      // allow "b7" for a block at least 7 spaces wide
      if (!ascii_isdigit(regtype.data[1])) {
        return false;
      }
      const char *p = regtype.data+1;
      reg->y_width = getdigits_int((char_u **)&p, false, 1) - 1;
      if (regtype.size > (size_t)(p-regtype.data)) {
        return false;
      }
    }
  
    reg->y_array = xcalloc(lines, sizeof(uint8_t *));
    reg->y_size = lines;
    reg->additional_data = NULL;
    reg->timestamp = 0;
    return true;
  }
  
  void finish_yankreg_from_object(yankreg_T *reg, bool clipboard_adjust)
  {
    if (reg->y_size > 0 && strlen((char *)reg->y_array[reg->y_size-1]) == 0) {
      // a known-to-be charwise yank might have a final linebreak
      // but otherwise there is no line after the final newline
      if (reg->y_type != kMTCharWise) {
        if (reg->y_type == kMTUnknown || clipboard_adjust) {
          xfree(reg->y_array[reg->y_size-1]);
          reg->y_size--;
        }
        if (reg->y_type == kMTUnknown) {
          reg->y_type = kMTLineWise;
        }
      }
    } else {
      if (reg->y_type == kMTUnknown) {
        reg->y_type = kMTCharWise;
      }
    }
  
    if (reg->y_type == kMTBlockWise) {
      size_t maxlen = 0;
      for (size_t i = 0; i < reg->y_size; i++) {
        size_t rowlen = STRLEN(reg->y_array[i]);
        if (rowlen > maxlen) {
          maxlen = rowlen;
        }
      }
      assert(maxlen <= INT_MAX);
      reg->y_width = MAX(reg->y_width, (int)maxlen - 1);
    }
  }
  
  static bool get_clipboard(int name, yankreg_T **target, bool quiet)
  {
    // show message on error
    bool errmsg = true;
  
    yankreg_T *reg = adjust_clipboard_name(&name, quiet, false);
    if (reg == NULL) {
      return false;
    }
    free_register(reg);
  
    list_T *const args = tv_list_alloc(1);
    const char regname = (char)name;
    tv_list_append_string(args, &regname, 1);
  
    typval_T result = eval_call_provider("clipboard", "get", args, false);
  
    if (result.v_type != VAR_LIST) {
      if (result.v_type == VAR_NUMBER && result.vval.v_number == 0) {
        // failure has already been indicated by provider
        errmsg = false;
      }
      goto err;
    }
  
    list_T *res = result.vval.v_list;
    list_T *lines = NULL;
    if (tv_list_len(res) == 2
        && TV_LIST_ITEM_TV(tv_list_first(res))->v_type == VAR_LIST) {
      lines = TV_LIST_ITEM_TV(tv_list_first(res))->vval.v_list;
      if (TV_LIST_ITEM_TV(tv_list_last(res))->v_type != VAR_STRING) {
        goto err;
      }
      char_u *regtype = TV_LIST_ITEM_TV(tv_list_last(res))->vval.v_string;
      if (regtype == NULL || strlen((char *)regtype) > 1) {
        goto err;
      }
      switch (regtype[0]) {
      case 0:
        reg->y_type = kMTUnknown;
        break;
      case 'v': case 'c':
        reg->y_type = kMTCharWise;
        break;
      case 'V': case 'l':
        reg->y_type = kMTLineWise;
        break;
      case 'b': case Ctrl_V:
        reg->y_type = kMTBlockWise;
        break;
      default:
        goto err;
      }
    } else {
      lines = res;
      // provider did not specify regtype, calculate it below
      reg->y_type = kMTUnknown;
    }
  
    reg->y_array = xcalloc((size_t)tv_list_len(lines), sizeof(char_u *));
    reg->y_size = (size_t)tv_list_len(lines);
    reg->additional_data = NULL;
    reg->timestamp = 0;
    // Timestamp is not saved for clipboard registers because clipboard registers
    // are not saved in the ShaDa file.
  
    size_t tv_idx = 0;
    TV_LIST_ITER_CONST(lines, li, {
      if (TV_LIST_ITEM_TV(li)->v_type != VAR_STRING) {
        goto err;
      }
      reg->y_array[tv_idx++] = (char_u *)xstrdupnul(
          (const char *)TV_LIST_ITEM_TV(li)->vval.v_string);
    });
  
    if (reg->y_size > 0 && strlen((char*)reg->y_array[reg->y_size-1]) == 0) {
      // a known-to-be charwise yank might have a final linebreak
      // but otherwise there is no line after the final newline
      if (reg->y_type != kMTCharWise) {
        xfree(reg->y_array[reg->y_size-1]);
        reg->y_size--;
        if (reg->y_type == kMTUnknown) {
          reg->y_type = kMTLineWise;
        }
      }
    } else {
      if (reg->y_type == kMTUnknown) {
        reg->y_type = kMTCharWise;
      }
    }
  
    if (reg->y_type == kMTBlockWise) {
      size_t maxlen = 0;
      for (size_t i = 0; i < reg->y_size; i++) {
        size_t rowlen = STRLEN(reg->y_array[i]);
        if (rowlen > maxlen) {
          maxlen = rowlen;
        }
      }
      assert(maxlen <= INT_MAX);
      reg->y_width = (int)maxlen - 1;
    }
  
    *target = reg;
    return true;
  
  err:
    if (reg->y_array) {
      for (size_t i = 0; i < reg->y_size; i++) {
        xfree(reg->y_array[i]);
      }
      xfree(reg->y_array);
    }
    reg->y_array = NULL;
    reg->y_size = 0;
    reg->additional_data = NULL;
    reg->timestamp = 0;
    if (errmsg) {
      EMSG("clipboard: provider returned invalid data");
    }
    *target = reg;
    return false;
  }
  
  static void set_clipboard(int name, yankreg_T *reg)
  {
    if (!adjust_clipboard_name(&name, false, true)) {
      return;
    }
  
    list_T *const lines = tv_list_alloc(
        (ptrdiff_t)reg->y_size + (reg->y_type != kMTCharWise));
  
    for (size_t i = 0; i < reg->y_size; i++) {
      tv_list_append_string(lines, (const char *)reg->y_array[i], -1);
    }
  
    char regtype;
    switch (reg->y_type) {
      case kMTLineWise: {
        regtype = 'V';
        tv_list_append_string(lines, NULL, 0);
        break;
      }
      case kMTCharWise: {
        regtype = 'v';
        break;
      }
      case kMTBlockWise: {
        regtype = 'b';
        tv_list_append_string(lines, NULL, 0);
        break;
      }
      case kMTUnknown: {
        assert(false);
      }
    }
  
    list_T *args = tv_list_alloc(3);
    tv_list_append_list(args, lines);
    tv_list_append_string(args, &regtype, 1);  // -V614
    tv_list_append_string(args, ((char[]) { (char)name }), 1);
  
    (void)eval_call_provider("clipboard", "set", args, true);
  }
  
  /// Avoid slow things (clipboard) during batch operations (while/for-loops).
  void start_batch_changes(void)
  {
    if (++batch_change_count > 1) {
      return;
    }
    clipboard_delay_update = true;
  }
  
  /// Counterpart to start_batch_changes().
  void end_batch_changes(void)
  {
    if (--batch_change_count > 0) {
      // recursive
      return;
    }
    clipboard_delay_update = false;
    if (clipboard_needs_update) {
      // must be before, as set_clipboard will invoke
      // start/end_batch_changes recursively
      clipboard_needs_update = false;
      // unnamed ("implicit" clipboard)
      set_clipboard(NUL, y_previous);
    }
  }
  
  int save_batch_count(void)
  {
    int save_count = batch_change_count;
    batch_change_count = 0;
    clipboard_delay_update = false;
    if (clipboard_needs_update) {
      clipboard_needs_update = false;
      // unnamed ("implicit" clipboard)
      set_clipboard(NUL, y_previous);
    }
    return save_count;
  }
  
  void restore_batch_count(int save_count)
  {
    assert(batch_change_count == 0);
    batch_change_count = save_count;
    if (batch_change_count > 0) {
      clipboard_delay_update = true;
    }
  }
  
  
  /// Check whether register is empty
  static inline bool reg_empty(const yankreg_T *const reg)
    FUNC_ATTR_PURE
  {
    return (reg->y_array == NULL
            || reg->y_size == 0
            || (reg->y_size == 1
                && reg->y_type == kMTCharWise
                && *(reg->y_array[0]) == NUL));
  }
  
  /// Iterate over global registers.
  ///
  /// @see op_register_iter
  const void *op_global_reg_iter(const void *const iter, char *const name,
                                 yankreg_T *const reg, bool *is_unnamed)
    FUNC_ATTR_NONNULL_ARG(2, 3, 4) FUNC_ATTR_WARN_UNUSED_RESULT
  {
    return op_reg_iter(iter, y_regs, name, reg, is_unnamed);
  }
  
  /// Iterate over registers `regs`.
  ///
  /// @param[in]   iter      Iterator. Pass NULL to start iteration.
  /// @param[in]   regs      Registers list to be iterated.
  /// @param[out]  name      Register name.
  /// @param[out]  reg       Register contents.
  ///
  /// @return Pointer that must be passed to next `op_register_iter` call or
  ///         NULL if iteration is over.
  const void *op_reg_iter(const void *const iter, const yankreg_T *const regs,
                          char *const name, yankreg_T *const reg,
                          bool *is_unnamed)
    FUNC_ATTR_NONNULL_ARG(3, 4, 5) FUNC_ATTR_WARN_UNUSED_RESULT
  {
    *name = NUL;
    const yankreg_T *iter_reg = (iter == NULL
                                 ? &(regs[0])
                                 : (const yankreg_T *const)iter);
    while (iter_reg - &(regs[0]) < NUM_SAVED_REGISTERS && reg_empty(iter_reg)) {
      iter_reg++;
    }
    if (iter_reg - &(regs[0]) == NUM_SAVED_REGISTERS || reg_empty(iter_reg)) {
      return NULL;
    }
    int iter_off = (int)(iter_reg - &(regs[0]));
    *name = (char)get_register_name(iter_off);
    *reg = *iter_reg;
    *is_unnamed = (iter_reg == y_previous);
    while (++iter_reg - &(regs[0]) < NUM_SAVED_REGISTERS) {
      if (!reg_empty(iter_reg)) {
        return (void *) iter_reg;
      }
    }
    return NULL;
  }
  
  /// Get a number of non-empty registers
  size_t op_reg_amount(void)
    FUNC_ATTR_WARN_UNUSED_RESULT
  {
    size_t ret = 0;
    for (size_t i = 0; i < NUM_SAVED_REGISTERS; i++) {
      if (!reg_empty(y_regs + i)) {
        ret++;
      }
    }
    return ret;
  }
  
  /// Set register to a given value
  ///
  /// @param[in]  name  Register name.
  /// @param[in]  reg  Register value.
  /// @param[in]  is_unnamed  Whether to set the unnamed regiseter to reg
  ///
  /// @return true on success, false on failure.
  bool op_reg_set(const char name, const yankreg_T reg, bool is_unnamed)
  {
    int i = op_reg_index(name);
    if (i == -1) {
      return false;
    }
    free_register(&y_regs[i]);
    y_regs[i] = reg;
  
    if (is_unnamed) {
      y_previous = &y_regs[i];
    }
    return true;
  }
  
  /// Get register with the given name
  ///
  /// @param[in]  name  Register name.
  ///
  /// @return Pointer to the register contents or NULL.
  const yankreg_T *op_reg_get(const char name)
  {
    int i = op_reg_index(name);
    if (i == -1) {
      return NULL;
    }
    return &y_regs[i];
  }
  
  /// Set the previous yank register
  ///
  /// @param[in]  name  Register name.
  ///
  /// @return true on success, false on failure.
  bool op_reg_set_previous(const char name)
    FUNC_ATTR_WARN_UNUSED_RESULT
  {
    int i = op_reg_index(name);
    if (i == -1) {
      return false;
    }
  
    y_previous = &y_regs[i];
    return true;
  }
  