text: /*
  ** $Id: llex.c,v 2.59 2011/11/30 12:43:51 roberto Exp $
  ** Lexical Analyzer
  ** See Copyright Notice in lua.h
  */
  
  
  #include <locale.h>
  #include <string.h>
  
  #define llex_c
  #define LUA_CORE
  
  #include "lua.h"
  
  #include "lctype.h"
  #include "ldo.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>", "<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_SIZET/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;
    for (i=0; i<NUM_RESERVED; i++) {
      TString *ts = luaS_new(L, luaX_tokens[i]);
      luaS_fix(ts);  /* reserved words are never collected */
      ts->tsv.reserved = cast_byte(i+1);  /* reserved word */
    }
  }
  
  
  const char *luaX_token2str (LexState *ls, int token) {
    if (token < FIRST_RESERVED) {
      lua_assert(token == cast(unsigned char, token));
      return (lisprint(token)) ? luaO_pushfstring(ls->L, LUA_QL("%c"), token) :
                                luaO_pushfstring(ls->L, "char(%d)", token);
    }
    else {
      const char *s = luaX_tokens[token - FIRST_RESERVED];
      if (token < TK_EOS)
        return luaO_pushfstring(ls->L, LUA_QS, s);
      else
        return s;
    }
  }
  
  
  static const char *txtToken (LexState *ls, int token) {
    switch (token) {
      case TK_NAME:
      case TK_STRING:
      case TK_NUMBER:
        save(ls, '\0');
        return luaO_pushfstring(ls->L, LUA_QS, luaZ_buffer(ls->buff));
      default:
        return luaX_token2str(ls, token);
    }
  }
  
  
  static l_noret lexerror (LexState *ls, const char *msg, int token) {
    char buff[LUA_IDSIZE];
    luaO_chunkid(buff, getstr(ls->source), LUA_IDSIZE);
    msg = luaO_pushfstring(ls->L, "%s:%d: %s", buff, ls->linenumber, msg);
    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 function's table so that
  ** it will not be collected until the end of the function's compilation
  ** (by that time it should be anchored in function's prototype)
  */
  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->fs->h, L->top - 1);
    if (ttisnil(o)) {  /* not in use yet? (see 'addK') */
      /* 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);
    }
    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)
      luaX_syntaxerror(ls, "chunk has too many lines");
  }
  
  
  void luaX_setinput (lua_State *L, LexState *ls, ZIO *z, TString *source,
                      int firstchar) {
    ls->decpoint = '.';
    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_new(L, LUA_ENV);  /* create env name */
    luaS_fix(ls->envn);  /* never collect this name */
    luaZ_resizebuffer(ls->L, ls->buff, LUA_MINBUFFER);  /* initialize buffer */
  }
  
  
  
  /*
  ** =======================================================
  ** LEXICAL ANALYZER
  ** =======================================================
  */
  
  
  
  static int check_next (LexState *ls, const char *set) {
    if (ls->current == '\0' || !strchr(set, ls->current))
      return 0;
    save_and_next(ls);
    return 1;
  }
  
  
  /*
  ** change all characters 'from' in buffer to 'to'
  */
  static void buffreplace (LexState *ls, char from, char to) {
    size_t n = luaZ_bufflen(ls->buff);
    char *p = luaZ_buffer(ls->buff);
    while (n--)
      if (p[n] == from) p[n] = to;
  }
  
  
  #if !defined(getlocaledecpoint)
  #define getlocaledecpoint()	(localeconv()->decimal_point[0])
  #endif
  
  
  #define buff2d(b,e)	luaO_str2d(luaZ_buffer(b), luaZ_bufflen(b) - 1, e)
  
  /*
  ** in case of format error, try to change decimal point separator to
  ** the one defined in the current locale and check again
  */
  static void trydecpoint (LexState *ls, SemInfo *seminfo) {
    char old = ls->decpoint;
    ls->decpoint = getlocaledecpoint();
    buffreplace(ls, old, ls->decpoint);  /* try new decimal separator */
    if (!buff2d(ls->buff, &seminfo->r)) {
      /* format error with correct decimal point: no more options */
      buffreplace(ls, ls->decpoint, '.');  /* undo change (for error message) */
      lexerror(ls, "malformed number", TK_NUMBER);
    }
  }
  
  
  /* LUA_NUMBER */
  static void read_numeral (LexState *ls, SemInfo *seminfo) {
    lua_assert(lisdigit(ls->current));
    do {
      save_and_next(ls);
      if (check_next(ls, "EePp"))  /* exponent part? */
        check_next(ls, "+-");  /* optional exponent sign */
    } while (lislalnum(ls->current) || ls->current == '.');
    save(ls, '\0');
    buffreplace(ls, '.', ls->decpoint);  /* follow locale for decimal point */
    if (!buff2d(ls->buff, &seminfo->r))  /* format error? */
      trydecpoint(ls, seminfo); /* try to update decimal point separator */
  }
  
  
  /*
  ** skip a sequence '[=*[' or ']=*]' and return its number of '='s or
  ** -1 if sequence is malformed
  */
  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) {
    save_and_next(ls);  /* skip 2nd `[' */
    if (currIsNewline(ls))  /* string starts with a newline? */
      inclinenumber(ls);  /* skip it */
    for (;;) {
      switch (ls->current) {
        case EOZ:
          lexerror(ls, (seminfo) ? "unfinished long string" :
                                   "unfinished long comment", 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 escerror (LexState *ls, int *c, int n, const char *msg) {
    int i;
    luaZ_resetbuffer(ls->buff);  /* prepare error message */
    save(ls, '\\');
    for (i = 0; i < n && c[i] != EOZ; i++)
      save(ls, c[i]);
    lexerror(ls, msg, TK_STRING);
  }
  
  
  static int readhexaesc (LexState *ls) {
    int c[3], i;  /* keep input for error message */
    int r = 0;  /* result accumulator */
    c[0] = 'x';  /* for error message */
    for (i = 1; i < 3; i++) {  /* read two hexa digits */
      c[i] = next(ls);
      if (!lisxdigit(c[i]))
        escerror(ls, c, i + 1, "hexadecimal digit expected");
      r = (r << 4) + luaO_hexavalue(c[i]);
    }
    return r;
  }
  
  
  static int readdecesc (LexState *ls) {
    int c[3], i;
    int r = 0;  /* result accumulator */
    for (i = 0; i < 3 && lisdigit(ls->current); i++) {  /* read up to 3 digits */
      c[i] = ls->current;
      r = 10*r + c[i] - '0';
      next(ls);
    }
    if (r > UCHAR_MAX)
      escerror(ls, c, i, "decimal escape too large");
    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 */
          next(ls);  /* do not save the `\' */
          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 '\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 */
              next(ls);  /* skip the 'z' */
              while (lisspace(ls->current)) {
                if (currIsNewline(ls)) inclinenumber(ls);
                else next(ls);
              }
              goto no_save;
            }
            default: {
              if (!lisdigit(ls->current))
                escerror(ls, &ls->current, 1, "invalid escape sequence");
              /* digital escape \ddd */
              c = readdecesc(ls);
              goto only_save;
            }
          }
         read_save: next(ls);  /* read next character */
         only_save: save(ls, c);  /* save 'c' */
         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) return '[';
          else lexerror(ls, "invalid long string delimiter", TK_STRING);
        }
        case '=': {
          next(ls);
          if (ls->current != '=') return '=';
          else { next(ls); return TK_EQ; }
        }
        case '<': {
          next(ls);
          if (ls->current != '=') return '<';
          else { next(ls); return TK_LE; }
        }
        case '>': {
          next(ls);
          if (ls->current != '=') return '>';
          else { next(ls); return TK_GE; }
        }
        case '~': {
          next(ls);
          if (ls->current != '=') return '~';
          else { next(ls); return TK_NE; }
        }
        case ':': {
          next(ls);
          if (ls->current != ':') return ':';
          else { next(ls); return TK_DBCOLON; }
        }
        case '"': case '\'': {  /* short literal strings */
          read_string(ls, ls->current, seminfo);
          return TK_STRING;
        }
        case '.': {  /* '.', '..', '...', or number */
          save_and_next(ls);
          if (check_next(ls, ".")) {
            if (check_next(ls, "."))
              return TK_DOTS;   /* '...' */
            else return TK_CONCAT;   /* '..' */
          }
          else if (!lisdigit(ls->current)) return '.';
          /* else go through */
        }
        case '0': case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9': {
          read_numeral(ls, seminfo);
          return TK_NUMBER;
        }
        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 (ts->tsv.reserved > 0)  /* reserved word? */
              return ts->tsv.reserved - 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;
  }
  
  