text: /*
  ** $Id: llex.c,v 2.96.1.1 2017/04/19 17:20:42 roberto Exp $
  ** Lexical Analyzer
  ** See Copyright Notice in lua.h
  */
  
  #define llex_c
  #define LUA_CORE
  
  #include "lprefix.h"
  
  
  #include <locale.h>
  #include <string.h>
  
  #include "lua.h"
  
  #include "lctype.h"
  #include "ldebug.h"
  #include "ldo.h"
  #include "lgc.h"
  #include "llex.h"
  #include "lobject.h"
  #include "lparser.h"
  #include "lstate.h"
  #include "lstring.h"
  #include "ltable.h"
  #include "lzio.h"
  
  
  
  #define next(ls) (ls->current = zgetc(ls->z))
  
  
  
  #define currIsNewline(ls)	(ls->current == '\n' || ls->current == '\r')
  
  
  /* ORDER RESERVED */
  static const char *const luaX_tokens [] = {
      "and", "break", "do", "else", "elseif",
      "end", "false", "for", "function", "goto", "if",
      "in", "local", "nil", "not", "or", "repeat",
      "return", "then", "true", "until", "while",
      "//", "..", "...", "==", ">=", "<=", "~=",
      "<<", ">>", "::", "<eof>",
      "<number>", "<integer>", "<name>", "<string>"
  };
  
  
  #define save_and_next(ls) (save(ls, ls->current), next(ls))
  
  
  static l_noret lexerror (LexState *ls, const char *msg, int token);
  
  
  static void save (LexState *ls, int c) {
    Mbuffer *b = ls->buff;
    if (luaZ_bufflen(b) + 1 > luaZ_sizebuffer(b)) {
      size_t newsize;
      if (luaZ_sizebuffer(b) >= MAX_SIZE/2)
        lexerror(ls, "lexical element too long", 0);
      newsize = luaZ_sizebuffer(b) * 2;
      luaZ_resizebuffer(ls->L, b, newsize);
    }
    b->buffer[luaZ_bufflen(b)++] = cast(char, c);
  }
  
  
  void luaX_init (lua_State *L) {
    int i;
    TString *e = luaS_newliteral(L, LUA_ENV);  /* create env name */
    luaC_fix(L, obj2gco(e));  /* never collect this name */
    for (i=0; i<NUM_RESERVED; i++) {
      TString *ts = luaS_new(L, luaX_tokens[i]);
      luaC_fix(L, obj2gco(ts));  /* reserved words are never collected */
      ts->extra = cast_byte(i+1);  /* reserved word */
    }
  }
  
  
  const char *luaX_token2str (LexState *ls, int token) {
    if (token < FIRST_RESERVED) {  /* single-byte symbols? */
      lua_assert(token == cast_uchar(token));
      return luaO_pushfstring(ls->L, "'%c'", token);
    }
    else {
      const char *s = luaX_tokens[token - FIRST_RESERVED];
      if (token < TK_EOS)  /* fixed format (symbols and reserved words)? */
        return luaO_pushfstring(ls->L, "'%s'", s);
      else  /* names, strings, and numerals */
        return s;
    }
  }
  
  
  static const char *txtToken (LexState *ls, int token) {
    switch (token) {
      case TK_NAME: case TK_STRING:
      case TK_FLT: case TK_INT:
        save(ls, '\0');
        return luaO_pushfstring(ls->L, "'%s'", luaZ_buffer(ls->buff));
      default:
        return luaX_token2str(ls, token);
    }
  }
  
  
  static l_noret lexerror (LexState *ls, const char *msg, int token) {
    msg = luaG_addinfo(ls->L, msg, ls->source, ls->linenumber);
    if (token)
      luaO_pushfstring(ls->L, "%s near %s", msg, txtToken(ls, token));
    luaD_throw(ls->L, LUA_ERRSYNTAX);
  }
  
  
  l_noret luaX_syntaxerror (LexState *ls, const char *msg) {
    lexerror(ls, msg, ls->t.token);
  }
  
  
  /*
  ** creates a new string and anchors it in scanner's table so that
  ** it will not be collected until the end of the compilation
  ** (by that time it should be anchored somewhere)
  */
  TString *luaX_newstring (LexState *ls, const char *str, size_t l) {
    lua_State *L = ls->L;
    TValue *o;  /* entry for 'str' */
    TString *ts = luaS_newlstr(L, str, l);  /* create new string */
    setsvalue2s(L, L->top++, ts);  /* temporarily anchor it in stack */
    o = luaH_set(L, ls->h, L->top - 1);
    if (ttisnil(o)) {  /* not in use yet? */
      /* boolean value does not need GC barrier;
         table has no metatable, so it does not need to invalidate cache */
      setbvalue(o, 1);  /* t[string] = true */
      luaC_checkGC(L);
    }
    else {  /* string already present */
      ts = tsvalue(keyfromval(o));  /* re-use value previously stored */
    }
    L->top--;  /* remove string from stack */
    return ts;
  }
  
  
  /*
  ** increment line number and skips newline sequence (any of
  ** \n, \r, \n\r, or \r\n)
  */
  static void inclinenumber (LexState *ls) {
    int old = ls->current;
    lua_assert(currIsNewline(ls));
    next(ls);  /* skip '\n' or '\r' */
    if (currIsNewline(ls) && ls->current != old)
      next(ls);  /* skip '\n\r' or '\r\n' */
    if (++ls->linenumber >= MAX_INT)
      lexerror(ls, "chunk has too many lines", 0);
  }
  
  
  void luaX_setinput (lua_State *L, LexState *ls, ZIO *z, TString *source,
                      int firstchar) {
    ls->t.token = 0;
    ls->L = L;
    ls->current = firstchar;
    ls->lookahead.token = TK_EOS;  /* no look-ahead token */
    ls->z = z;
    ls->fs = NULL;
    ls->linenumber = 1;
    ls->lastline = 1;
    ls->source = source;
    ls->envn = luaS_newliteral(L, LUA_ENV);  /* get env name */
    luaZ_resizebuffer(ls->L, ls->buff, LUA_MINBUFFER);  /* initialize buffer */
  }
  
  
  
  /*
  ** =======================================================
  ** LEXICAL ANALYZER
  ** =======================================================
  */
  
  
  static int check_next1 (LexState *ls, int c) {
    if (ls->current == c) {
      next(ls);
      return 1;
    }
    else return 0;
  }
  
  
  /*
  ** Check whether current char is in set 'set' (with two chars) and
  ** saves it
  */
  static int check_next2 (LexState *ls, const char *set) {
    lua_assert(set[2] == '\0');
    if (ls->current == set[0] || ls->current == set[1]) {
      save_and_next(ls);
      return 1;
    }
    else return 0;
  }
  
  
  /* LUA_NUMBER */
  /*
  ** this function is quite liberal in what it accepts, as 'luaO_str2num'
  ** will reject ill-formed numerals.
  */
  static int read_numeral (LexState *ls, SemInfo *seminfo) {
    TValue obj;
    const char *expo = "Ee";
    int first = ls->current;
    lua_assert(lisdigit(ls->current));
    save_and_next(ls);
    if (first == '0' && check_next2(ls, "xX"))  /* hexadecimal? */
      expo = "Pp";
    for (;;) {
      if (check_next2(ls, expo))  /* exponent part? */
        check_next2(ls, "-+");  /* optional exponent sign */
      if (lisxdigit(ls->current))
        save_and_next(ls);
      else if (ls->current == '.')
        save_and_next(ls);
      else break;
    }
    save(ls, '\0');
    if (luaO_str2num(luaZ_buffer(ls->buff), &obj) == 0)  /* format error? */
      lexerror(ls, "malformed number", TK_FLT);
    if (ttisinteger(&obj)) {
      seminfo->i = ivalue(&obj);
      return TK_INT;
    }
    else {
      lua_assert(ttisfloat(&obj));
      seminfo->r = fltvalue(&obj);
      return TK_FLT;
    }
  }
  
  
  /*
  ** skip a sequence '[=*[' or ']=*]'; if sequence is well formed, return
  ** its number of '='s; otherwise, return a negative number (-1 iff there
  ** are no '='s after initial bracket)
  */
  static int skip_sep (LexState *ls) {
    int count = 0;
    int s = ls->current;
    lua_assert(s == '[' || s == ']');
    save_and_next(ls);
    while (ls->current == '=') {
      save_and_next(ls);
      count++;
    }
    return (ls->current == s) ? count : (-count) - 1;
  }
  
  
  static void read_long_string (LexState *ls, SemInfo *seminfo, int sep) {
    int line = ls->linenumber;  /* initial line (for error message) */
    save_and_next(ls);  /* skip 2nd '[' */
    if (currIsNewline(ls))  /* string starts with a newline? */
      inclinenumber(ls);  /* skip it */
    for (;;) {
      switch (ls->current) {
        case EOZ: {  /* error */
          const char *what = (seminfo ? "string" : "comment");
          const char *msg = luaO_pushfstring(ls->L,
                       "unfinished long %s (starting at line %d)", what, line);
          lexerror(ls, msg, TK_EOS);
          break;  /* to avoid warnings */
        }
        case ']': {
          if (skip_sep(ls) == sep) {
            save_and_next(ls);  /* skip 2nd ']' */
            goto endloop;
          }
          break;
        }
        case '\n': case '\r': {
          save(ls, '\n');
          inclinenumber(ls);
          if (!seminfo) luaZ_resetbuffer(ls->buff);  /* avoid wasting space */
          break;
        }
        default: {
          if (seminfo) save_and_next(ls);
          else next(ls);
        }
      }
    } endloop:
    if (seminfo)
      seminfo->ts = luaX_newstring(ls, luaZ_buffer(ls->buff) + (2 + sep),
                                       luaZ_bufflen(ls->buff) - 2*(2 + sep));
  }
  
  
  static void esccheck (LexState *ls, int c, const char *msg) {
    if (!c) {
      if (ls->current != EOZ)
        save_and_next(ls);  /* add current to buffer for error message */
      lexerror(ls, msg, TK_STRING);
    }
  }
  
  
  static int gethexa (LexState *ls) {
    save_and_next(ls);
    esccheck (ls, lisxdigit(ls->current), "hexadecimal digit expected");
    return luaO_hexavalue(ls->current);
  }
  
  
  static int readhexaesc (LexState *ls) {
    int r = gethexa(ls);
    r = (r << 4) + gethexa(ls);
    luaZ_buffremove(ls->buff, 2);  /* remove saved chars from buffer */
    return r;
  }
  
  
  static unsigned long readutf8esc (LexState *ls) {
    unsigned long r;
    int i = 4;  /* chars to be removed: '\', 'u', '{', and first digit */
    save_and_next(ls);  /* skip 'u' */
    esccheck(ls, ls->current == '{', "missing '{'");
    r = gethexa(ls);  /* must have at least one digit */
    while ((save_and_next(ls), lisxdigit(ls->current))) {
      i++;
      r = (r << 4) + luaO_hexavalue(ls->current);
      esccheck(ls, r <= 0x10FFFF, "UTF-8 value too large");
    }
    esccheck(ls, ls->current == '}', "missing '}'");
    next(ls);  /* skip '}' */
    luaZ_buffremove(ls->buff, i);  /* remove saved chars from buffer */
    return r;
  }
  
  
  static void utf8esc (LexState *ls) {
    char buff[UTF8BUFFSZ];
    int n = luaO_utf8esc(buff, readutf8esc(ls));
    for (; n > 0; n--)  /* add 'buff' to string */
      save(ls, buff[UTF8BUFFSZ - n]);
  }
  
  
  static int readdecesc (LexState *ls) {
    int i;
    int r = 0;  /* result accumulator */
    for (i = 0; i < 3 && lisdigit(ls->current); i++) {  /* read up to 3 digits */
      r = 10*r + ls->current - '0';
      save_and_next(ls);
    }
    esccheck(ls, r <= UCHAR_MAX, "decimal escape too large");
    luaZ_buffremove(ls->buff, i);  /* remove read digits from buffer */
    return r;
  }
  
  
  static void read_string (LexState *ls, int del, SemInfo *seminfo) {
    save_and_next(ls);  /* keep delimiter (for error messages) */
    while (ls->current != del) {
      switch (ls->current) {
        case EOZ:
          lexerror(ls, "unfinished string", TK_EOS);
          break;  /* to avoid warnings */
        case '\n':
        case '\r':
          lexerror(ls, "unfinished string", TK_STRING);
          break;  /* to avoid warnings */
        case '\\': {  /* escape sequences */
          int c;  /* final character to be saved */
          save_and_next(ls);  /* keep '\\' for error messages */
          switch (ls->current) {
            case 'a': c = '\a'; goto read_save;
            case 'b': c = '\b'; goto read_save;
            case 'f': c = '\f'; goto read_save;
            case 'n': c = '\n'; goto read_save;
            case 'r': c = '\r'; goto read_save;
            case 't': c = '\t'; goto read_save;
            case 'v': c = '\v'; goto read_save;
            case 'x': c = readhexaesc(ls); goto read_save;
            case 'u': utf8esc(ls);  goto no_save;
            case '\n': case '\r':
              inclinenumber(ls); c = '\n'; goto only_save;
            case '\\': case '\"': case '\'':
              c = ls->current; goto read_save;
            case EOZ: goto no_save;  /* will raise an error next loop */
            case 'z': {  /* zap following span of spaces */
              luaZ_buffremove(ls->buff, 1);  /* remove '\\' */
              next(ls);  /* skip the 'z' */
              while (lisspace(ls->current)) {
                if (currIsNewline(ls)) inclinenumber(ls);
                else next(ls);
              }
              goto no_save;
            }
            default: {
              esccheck(ls, lisdigit(ls->current), "invalid escape sequence");
              c = readdecesc(ls);  /* digital escape '\ddd' */
              goto only_save;
            }
          }
         read_save:
           next(ls);
           /* go through */
         only_save:
           luaZ_buffremove(ls->buff, 1);  /* remove '\\' */
           save(ls, c);
           /* go through */
         no_save: break;
        }
        default:
          save_and_next(ls);
      }
    }
    save_and_next(ls);  /* skip delimiter */
    seminfo->ts = luaX_newstring(ls, luaZ_buffer(ls->buff) + 1,
                                     luaZ_bufflen(ls->buff) - 2);
  }
  
  
  static int llex (LexState *ls, SemInfo *seminfo) {
    luaZ_resetbuffer(ls->buff);
    for (;;) {
      switch (ls->current) {
        case '\n': case '\r': {  /* line breaks */
          inclinenumber(ls);
          break;
        }
        case ' ': case '\f': case '\t': case '\v': {  /* spaces */
          next(ls);
          break;
        }
        case '-': {  /* '-' or '--' (comment) */
          next(ls);
          if (ls->current != '-') return '-';
          /* else is a comment */
          next(ls);
          if (ls->current == '[') {  /* long comment? */
            int sep = skip_sep(ls);
            luaZ_resetbuffer(ls->buff);  /* 'skip_sep' may dirty the buffer */
            if (sep >= 0) {
              read_long_string(ls, NULL, sep);  /* skip long comment */
              luaZ_resetbuffer(ls->buff);  /* previous call may dirty the buff. */
              break;
            }
          }
          /* else short comment */
          while (!currIsNewline(ls) && ls->current != EOZ)
            next(ls);  /* skip until end of line (or end of file) */
          break;
        }
        case '[': {  /* long string or simply '[' */
          int sep = skip_sep(ls);
          if (sep >= 0) {
            read_long_string(ls, seminfo, sep);
            return TK_STRING;
          }
          else if (sep != -1)  /* '[=...' missing second bracket */
            lexerror(ls, "invalid long string delimiter", TK_STRING);
          return '[';
        }
        case '=': {
          next(ls);
          if (check_next1(ls, '=')) return TK_EQ;
          else return '=';
        }
        case '<': {
          next(ls);
          if (check_next1(ls, '=')) return TK_LE;
          else if (check_next1(ls, '<')) return TK_SHL;
          else return '<';
        }
        case '>': {
          next(ls);
          if (check_next1(ls, '=')) return TK_GE;
          else if (check_next1(ls, '>')) return TK_SHR;
          else return '>';
        }
        case '/': {
          next(ls);
          if (check_next1(ls, '/')) return TK_IDIV;
          else return '/';
        }
        case '~': {
          next(ls);
          if (check_next1(ls, '=')) return TK_NE;
          else return '~';
        }
  #ifdef SP2_LUA_EXTENTIONS
        case '!': {
          next(ls);
          if (check_next1(ls, '=')) return TK_NE;
          else return '!';
        }
        case '&': {
          next(ls);
          if (check_next1(ls, '&')) return TK_AND;
          else return '&';
        }
        case '|': {
          next(ls);
          if (check_next1(ls, '|')) return TK_OR;
          else return '|';
        }
  #endif
        case ':': {
          next(ls);
          if (check_next1(ls, ':')) return TK_DBCOLON;
          else return ':';
        }
        case '"': case '\'': {  /* short literal strings */
          read_string(ls, ls->current, seminfo);
          return TK_STRING;
        }
        case '.': {  /* '.', '..', '...', or number */
          save_and_next(ls);
          if (check_next1(ls, '.')) {
            if (check_next1(ls, '.'))
              return TK_DOTS;   /* '...' */
            else return TK_CONCAT;   /* '..' */
          }
          else if (!lisdigit(ls->current)) return '.';
          else return read_numeral(ls, seminfo);
        }
        case '0': case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9': {
          return read_numeral(ls, seminfo);
        }
        case EOZ: {
          return TK_EOS;
        }
        default: {
          if (lislalpha(ls->current)) {  /* identifier or reserved word? */
            TString *ts;
            do {
              save_and_next(ls);
            } while (lislalnum(ls->current));
            ts = luaX_newstring(ls, luaZ_buffer(ls->buff),
                                    luaZ_bufflen(ls->buff));
            seminfo->ts = ts;
            if (isreserved(ts))  /* reserved word? */
              return ts->extra - 1 + FIRST_RESERVED;
            else {
              return TK_NAME;
            }
          }
          else {  /* single-char tokens (+ - / ...) */
            int c = ls->current;
            next(ls);
            return c;
          }
        }
      }
    }
  }
  
  
  void luaX_next (LexState *ls) {
    ls->lastline = ls->linenumber;
    if (ls->lookahead.token != TK_EOS) {  /* is there a look-ahead token? */
      ls->t = ls->lookahead;  /* use this one */
      ls->lookahead.token = TK_EOS;  /* and discharge it */
    }
    else
      ls->t.token = llex(ls, &ls->t.seminfo);  /* read next token */
  }
  
  
  int luaX_lookahead (LexState *ls) {
    lua_assert(ls->lookahead.token == TK_EOS);
    ls->lookahead.token = llex(ls, &ls->lookahead.seminfo);
    return ls->lookahead.token;
  }
  
  