text: /*
  ** $Id: lstrlib.c,v 1.132.1.5 2010/05/14 15:34:19 roberto Exp $
  ** Standard library for string operations and pattern-matching
  ** See Copyright Notice in lua.h
  */
  
  #define lstrlib_c
  #define LUA_LIB
  #define LUAC_CROSS_FILE
  
  #include "lua.h"
  #include C_HEADER_STDIO
  #include C_HEADER_STRING
  
  #include "lauxlib.h"
  #include "lrotable.h"
  #include "lualib.h"
  
  /* macro to `unsign' a character */
  #define uchar(c) ((unsigned char)(c))
  
  static int str_len(lua_State *L)
  {
      size_t l;
      luaL_checklstring(L, 1, &l);
      lua_pushinteger(L, l);
      return 1;
  }
  
  static ptrdiff_t posrelat(ptrdiff_t pos, size_t len)
  {
      /* relative string position: negative means back from end */
      if (pos < 0)
          pos += (ptrdiff_t)len + 1;
      return (pos >= 0) ? pos : 0;
  }
  
  static int str_sub(lua_State *L)
  {
      size_t l;
      const char *s = luaL_checklstring(L, 1, &l);
      ptrdiff_t start = posrelat(luaL_checkinteger(L, 2), l);
      ptrdiff_t end = posrelat(luaL_optinteger(L, 3, -1), l);
      if (start < 1)
          start = 1;
      if (end > (ptrdiff_t)l)
          end = (ptrdiff_t)l;
      if (start <= end)
          lua_pushlstring(L, s + start - 1, end - start + 1);
      else
          lua_pushliteral(L, "");
      return 1;
  }
  
  static int str_reverse(lua_State *L)
  {
      size_t l;
      luaL_Buffer b;
      const char *s = luaL_checklstring(L, 1, &l);
      luaL_buffinit(L, &b);
      while (l--) luaL_addchar(&b, s[l]);
      luaL_pushresult(&b);
      return 1;
  }
  
  static int str_lower(lua_State *L)
  {
      size_t l;
      size_t i;
      luaL_Buffer b;
      const char *s = luaL_checklstring(L, 1, &l);
      luaL_buffinit(L, &b);
      for (i = 0; i < l; i++) luaL_addchar(&b, tolower(uchar(s[i])));
      luaL_pushresult(&b);
      return 1;
  }
  
  static int str_upper(lua_State *L)
  {
      size_t l;
      size_t i;
      luaL_Buffer b;
      const char *s = luaL_checklstring(L, 1, &l);
      luaL_buffinit(L, &b);
      for (i = 0; i < l; i++) luaL_addchar(&b, toupper(uchar(s[i])));
      luaL_pushresult(&b);
      return 1;
  }
  
  static int str_rep(lua_State *L)
  {
      size_t l;
      luaL_Buffer b;
      const char *s = luaL_checklstring(L, 1, &l);
      int n = luaL_checkint(L, 2);
      luaL_buffinit(L, &b);
      while (n-- > 0) luaL_addlstring(&b, s, l);
      luaL_pushresult(&b);
      return 1;
  }
  
  static int str_byte(lua_State *L)
  {
      size_t l;
      const char *s = luaL_checklstring(L, 1, &l);
      ptrdiff_t posi = posrelat(luaL_optinteger(L, 2, 1), l);
      ptrdiff_t pose = posrelat(luaL_optinteger(L, 3, posi), l);
      int n, i;
      if (posi <= 0)
          posi = 1;
      if ((size_t)pose > l)
          pose = l;
      if (posi > pose)
          return 0; /* empty interval; return no values */
      n = (int)(pose - posi + 1);
      if (posi + n <= pose) /* overflow? */
          luaL_error(L, "string slice too long");
      luaL_checkstack(L, n, "string slice too long");
      for (i = 0; i < n; i++) lua_pushinteger(L, uchar(s[posi + i - 1]));
      return n;
  }
  
  static int str_char(lua_State *L)
  {
      int n = lua_gettop(L); /* number of arguments */
      int i;
      luaL_Buffer b;
      luaL_buffinit(L, &b);
      for (i = 1; i <= n; i++)
      {
          int c = luaL_checkint(L, i);
          luaL_argcheck(L, uchar(c) == c, i, "invalid value");
          luaL_addchar(&b, uchar(c));
      }
      luaL_pushresult(&b);
      return 1;
  }
  
  static int writer(lua_State *L, const void *b, size_t size, void *B)
  {
      (void)L;
      luaL_addlstring((luaL_Buffer *)B, (const char *)b, size);
      return 0;
  }
  
  static int str_dump(lua_State *L)
  {
      luaL_Buffer b;
      luaL_checktype(L, 1, LUA_TFUNCTION);
      lua_settop(L, 1);
      luaL_buffinit(L, &b);
      if (lua_dump(L, writer, &b) != 0)
          luaL_error(L, "unable to dump given function");
      luaL_pushresult(&b);
      return 1;
  }
  
  /*
  ** {======================================================
  ** PATTERN MATCHING
  ** =======================================================
  */
  
  #define CAP_UNFINISHED (-1)
  #define CAP_POSITION (-2)
  
  typedef struct MatchState
  {
      const char *src_init; /* init of source string */
      const char *src_end;  /* end (`\0') of source string */
      lua_State *L;
      int level; /* total number of captures (finished or unfinished) */
      struct
      {
          const char *init;
          ptrdiff_t len;
      } capture[LUA_MAXCAPTURES];
  } MatchState;
  
  #define L_ESC '%'
  #define SPECIALS "^$*+?.([%-"
  
  static int check_capture(MatchState *ms, int l)
  {
      l -= '1';
      if (l < 0 || l >= ms->level || ms->capture[l].len == CAP_UNFINISHED)
          return luaL_error(ms->L, "invalid capture index");
      return l;
  }
  
  static int capture_to_close(MatchState *ms)
  {
      int level = ms->level;
      for (level--; level >= 0; level--)
          if (ms->capture[level].len == CAP_UNFINISHED)
              return level;
      return luaL_error(ms->L, "invalid pattern capture");
  }
  
  static const char *classend(MatchState *ms, const char *p)
  {
      switch (*p++)
      {
          case L_ESC:
          {
              if (*p == '\0')
                  luaL_error(ms->L, "malformed pattern (ends with " LUA_QL("%%") ")");
              return p + 1;
          }
          case '[':
          {
              if (*p == '^')
                  p++;
              do
              { /* look for a `]' */
                  if (*p == '\0')
                      luaL_error(ms->L, "malformed pattern (missing " LUA_QL("]") ")");
                  if (*(p++) == L_ESC && *p != '\0')
                      p++; /* skip escapes (e.g. `%]') */
              } while (*p != ']');
              return p + 1;
          }
          default:
          {
              return p;
          }
      }
  }
  
  static int match_class(int c, int cl)
  {
      int res;
      switch (tolower(cl))
      {
          case 'a':
              res = isalpha(c);
              break;
          case 'c':
              res = iscntrl(c);
              break;
          case 'd':
              res = isdigit(c);
              break;
          case 'l':
              res = islower(c);
              break;
          case 'p':
              res = ispunct(c);
              break;
          case 's':
              res = isspace(c);
              break;
          case 'u':
              res = isupper(c);
              break;
          case 'w':
              res = isalnum(c);
              break;
          case 'x':
              res = isxdigit(c);
              break;
          case 'z':
              res = (c == 0);
              break;
          default:
              return (cl == c);
      }
      return (islower(cl) ? res : !res);
  }
  
  static int matchbracketclass(int c, const char *p, const char *ec)
  {
      int sig = 1;
      if (*(p + 1) == '^')
      {
          sig = 0;
          p++; /* skip the `^' */
      }
      while (++p < ec)
      {
          if (*p == L_ESC)
          {
              p++;
              if (match_class(c, uchar(*p)))
                  return sig;
          }
          else if ((*(p + 1) == '-') && (p + 2 < ec))
          {
              p += 2;
              if (uchar(*(p - 2)) <= c && c <= uchar(*p))
                  return sig;
          }
          else if (uchar(*p) == c)
              return sig;
      }
      return !sig;
  }
  
  static int singlematch(int c, const char *p, const char *ep)
  {
      switch (*p)
      {
          case '.':
              return 1; /* matches any char */
          case L_ESC:
              return match_class(c, uchar(*(p + 1)));
          case '[':
              return matchbracketclass(c, p, ep - 1);
          default:
              return (uchar(*p) == c);
      }
  }
  
  static const char *match(MatchState *ms, const char *s, const char *p);
  
  static const char *matchbalance(MatchState *ms, const char *s, const char *p)
  {
      if (*p == 0 || *(p + 1) == 0)
          luaL_error(ms->L, "unbalanced pattern");
      if (*s != *p)
          return NULL;
      else
      {
          int b = *p;
          int e = *(p + 1);
          int cont = 1;
          while (++s < ms->src_end)
          {
              if (*s == e)
              {
                  if (--cont == 0)
                      return s + 1;
              }
              else if (*s == b)
                  cont++;
          }
      }
      return NULL; /* string ends out of balance */
  }
  
  static const char *max_expand(MatchState *ms, const char *s, const char *p, const char *ep)
  {
      ptrdiff_t i = 0; /* counts maximum expand for item */
      while ((s + i) < ms->src_end && singlematch(uchar(*(s + i)), p, ep)) i++;
      /* keeps trying to match with the maximum repetitions */
      while (i >= 0)
      {
          const char *res = match(ms, (s + i), ep + 1);
          if (res)
              return res;
          i--; /* else didn't match; reduce 1 repetition to try again */
      }
      return NULL;
  }
  
  static const char *min_expand(MatchState *ms, const char *s, const char *p, const char *ep)
  {
      for (;;)
      {
          const char *res = match(ms, s, ep + 1);
          if (res != NULL)
              return res;
          else if (s < ms->src_end && singlematch(uchar(*s), p, ep))
              s++; /* try with one more repetition */
          else
              return NULL;
      }
  }
  
  static const char *start_capture(MatchState *ms, const char *s, const char *p, int what)
  {
      const char *res;
      int level = ms->level;
      if (level >= LUA_MAXCAPTURES)
          luaL_error(ms->L, "too many captures");
      ms->capture[level].init = s;
      ms->capture[level].len = what;
      ms->level = level + 1;
      if ((res = match(ms, s, p)) == NULL) /* match failed? */
          ms->level--;                     /* undo capture */
      return res;
  }
  
  static const char *end_capture(MatchState *ms, const char *s, const char *p)
  {
      int l = capture_to_close(ms);
      const char *res;
      ms->capture[l].len = s - ms->capture[l].init; /* close capture */
      if ((res = match(ms, s, p)) == NULL)          /* match failed? */
          ms->capture[l].len = CAP_UNFINISHED;      /* undo capture */
      return res;
  }
  
  static const char *match_capture(MatchState *ms, const char *s, int l)
  {
      size_t len;
      l = check_capture(ms, l);
      len = ms->capture[l].len;
      if ((size_t)(ms->src_end - s) >= len && memcmp(ms->capture[l].init, s, len) == 0)
          return s + len;
      else
          return NULL;
  }
  
  static const char *match(MatchState *ms, const char *s, const char *p)
  {
  init: /* using goto's to optimize tail recursion */
      switch (*p)
      {
          case '(':
          {                        /* start capture */
              if (*(p + 1) == ')') /* position capture? */
                  return start_capture(ms, s, p + 2, CAP_POSITION);
              else
                  return start_capture(ms, s, p + 1, CAP_UNFINISHED);
          }
          case ')':
          { /* end capture */
              return end_capture(ms, s, p + 1);
          }
          case L_ESC:
          {
              switch (*(p + 1))
              {
                  case 'b':
                  { /* balanced string? */
                      s = matchbalance(ms, s, p + 2);
                      if (s == NULL)
                          return NULL;
                      p += 4;
                      goto init; /* else return match(ms, s, p+4); */
                  }
                  case 'f':
                  { /* frontier? */
                      const char *ep;
                      char previous;
                      p += 2;
                      if (*p != '[')
                          luaL_error(ms->L, "missing " LUA_QL("[") " after " LUA_QL("%%f") " in pattern");
                      ep = classend(ms, p); /* points to what is next */
                      previous = (s == ms->src_init) ? '\0' : *(s - 1);
                      if (matchbracketclass(uchar(previous), p, ep - 1) || !matchbracketclass(uchar(*s), p, ep - 1))
                          return NULL;
                      p = ep;
                      goto init; /* else return match(ms, s, ep); */
                  }
                  default:
                  {
                      if (isdigit(uchar(*(p + 1))))
                      { /* capture results (%0-%9)? */
                          s = match_capture(ms, s, uchar(*(p + 1)));
                          if (s == NULL)
                              return NULL;
                          p += 2;
                          goto init; /* else return match(ms, s, p+2) */
                      }
                      goto dflt; /* case default */
                  }
              }
          }
          case '\0':
          {             /* end of pattern */
              return s; /* match succeeded */
          }
          case '$':
          {
              if (*(p + 1) == '\0')                     /* is the `$' the last char in pattern? */
                  return (s == ms->src_end) ? s : NULL; /* check end of string */
              else
                  goto dflt;
          }
          default:
          dflt:
          {                                     /* it is a pattern item */
              const char *ep = classend(ms, p); /* points to what is next */
              int m = s < ms->src_end && singlematch(uchar(*s), p, ep);
              switch (*ep)
              {
                  case '?':
                  { /* optional */
                      const char *res;
                      if (m && ((res = match(ms, s + 1, ep + 1)) != NULL))
                          return res;
                      p = ep + 1;
                      goto init; /* else return match(ms, s, ep+1); */
                  }
                  case '*':
                  { /* 0 or more repetitions */
                      return max_expand(ms, s, p, ep);
                  }
                  case '+':
                  { /* 1 or more repetitions */
                      return (m ? max_expand(ms, s + 1, p, ep) : NULL);
                  }
                  case '-':
                  { /* 0 or more repetitions (minimum) */
                      return min_expand(ms, s, p, ep);
                  }
                  default:
                  {
                      if (!m)
                          return NULL;
                      s++;
                      p = ep;
                      goto init; /* else return match(ms, s+1, ep); */
                  }
              }
          }
      }
  }
  
  static const char *lmemfind(const char *s1, size_t l1, const char *s2, size_t l2)
  {
      if (l2 == 0)
          return s1; /* empty strings are everywhere */
      else if (l2 > l1)
          return NULL; /* avoids a negative `l1' */
      else
      {
          const char *init; /* to search for a `*s2' inside `s1' */
          l2--;             /* 1st char will be checked by `memchr' */
          l1 = l1 - l2;     /* `s2' cannot be found after that */
          while (l1 > 0 && (init = (const char *)memchr(s1, *s2, l1)) != NULL)
          {
              init++; /* 1st char is already checked */
              if (memcmp(init, s2 + 1, l2) == 0)
                  return init - 1;
              else
              { /* correct `l1' and `s1' to try again */
                  l1 -= init - s1;
                  s1 = init;
              }
          }
          return NULL; /* not found */
      }
  }
  
  static void push_onecapture(MatchState *ms, int i, const char *s, const char *e)
  {
      if (i >= ms->level)
      {
          if (i == 0)                           /* ms->level == 0, too */
              lua_pushlstring(ms->L, s, e - s); /* add whole match */
          else
              luaL_error(ms->L, "invalid capture index");
      }
      else
      {
          ptrdiff_t l = ms->capture[i].len;
          if (l == CAP_UNFINISHED)
              luaL_error(ms->L, "unfinished capture");
          if (l == CAP_POSITION)
              lua_pushinteger(ms->L, ms->capture[i].init - ms->src_init + 1);
          else
              lua_pushlstring(ms->L, ms->capture[i].init, l);
      }
  }
  
  static int push_captures(MatchState *ms, const char *s, const char *e)
  {
      int i;
      int nlevels = (ms->level == 0 && s) ? 1 : ms->level;
      luaL_checkstack(ms->L, nlevels, "too many captures");
      for (i = 0; i < nlevels; i++) push_onecapture(ms, i, s, e);
      return nlevels; /* number of strings pushed */
  }
  
  static int str_find_aux(lua_State *L, int find)
  {
      size_t l1, l2;
      const char *s = luaL_checklstring(L, 1, &l1);
      const char *p = luaL_checklstring(L, 2, &l2);
      ptrdiff_t init = posrelat(luaL_optinteger(L, 3, 1), l1) - 1;
      if (init < 0)
          init = 0;
      else if ((size_t)(init) > l1)
          init = (ptrdiff_t)l1;
      if (find && (lua_toboolean(L, 4) || /* explicit request? */
                   strpbrk(p, SPECIALS) == NULL))
      { /* or no special characters? */
          /* do a plain search */
          const char *s2 = lmemfind(s + init, l1 - init, p, l2);
          if (s2)
          {
              lua_pushinteger(L, s2 - s + 1);
              lua_pushinteger(L, s2 - s + l2);
              return 2;
          }
      }
      else
      {
          MatchState ms;
          int anchor = (*p == '^') ? (p++, 1) : 0;
          const char *s1 = s + init;
          ms.L = L;
          ms.src_init = s;
          ms.src_end = s + l1;
          do
          {
              const char *res;
              ms.level = 0;
              if ((res = match(&ms, s1, p)) != NULL)
              {
                  if (find)
                  {
                      lua_pushinteger(L, s1 - s + 1); /* start */
                      lua_pushinteger(L, res - s);    /* end */
                      return push_captures(&ms, NULL, 0) + 2;
                  }
                  else
                      return push_captures(&ms, s1, res);
              }
          } while (s1++ < ms.src_end && !anchor);
      }
      lua_pushnil(L); /* not found */
      return 1;
  }
  
  static int str_find(lua_State *L) { return str_find_aux(L, 1); }
  
  static int str_match(lua_State *L) { return str_find_aux(L, 0); }
  
  static int gmatch_aux(lua_State *L)
  {
      MatchState ms;
      size_t ls;
      const char *s = lua_tolstring(L, lua_upvalueindex(1), &ls);
      const char *p = lua_tostring(L, lua_upvalueindex(2));
      const char *src;
      ms.L = L;
      ms.src_init = s;
      ms.src_end = s + ls;
      for (src = s + (size_t)lua_tointeger(L, lua_upvalueindex(3)); src <= ms.src_end; src++)
      {
          const char *e;
          ms.level = 0;
          if ((e = match(&ms, src, p)) != NULL)
          {
              lua_Integer newstart = e - s;
              if (e == src)
                  newstart++; /* empty match? go at least one position */
              lua_pushinteger(L, newstart);
              lua_replace(L, lua_upvalueindex(3));
              return push_captures(&ms, src, e);
          }
      }
      return 0; /* not found */
  }
  
  static int gmatch(lua_State *L)
  {
      luaL_checkstring(L, 1);
      luaL_checkstring(L, 2);
      lua_settop(L, 2);
      lua_pushinteger(L, 0);
      lua_pushcclosure(L, gmatch_aux, 3);
      return 1;
  }
  
  #if LUA_OPTIMIZE_MEMORY == 0 || !defined(LUA_COMPAT_GFIND)
  static int gfind_nodef(lua_State *L)
  {
      return luaL_error(L, LUA_QL("string.gfind") " was renamed to " LUA_QL("string.gmatch"));
  }
  #endif
  
  static void add_s(MatchState *ms, luaL_Buffer *b, const char *s, const char *e)
  {
      size_t l, i;
      const char *news = lua_tolstring(ms->L, 3, &l);
      for (i = 0; i < l; i++)
      {
          if (news[i] != L_ESC)
              luaL_addchar(b, news[i]);
          else
          {
              i++; /* skip ESC */
              if (!isdigit(uchar(news[i])))
                  luaL_addchar(b, news[i]);
              else if (news[i] == '0')
                  luaL_addlstring(b, s, e - s);
              else
              {
                  push_onecapture(ms, news[i] - '1', s, e);
                  luaL_addvalue(b); /* add capture to accumulated result */
              }
          }
      }
  }
  
  static void add_value(MatchState *ms, luaL_Buffer *b, const char *s, const char *e)
  {
      lua_State *L = ms->L;
      switch (lua_type(L, 3))
      {
          case LUA_TNUMBER:
          case LUA_TSTRING:
          {
              add_s(ms, b, s, e);
              return;
          }
          case LUA_TFUNCTION:
          case LUA_TLIGHTFUNCTION:
          {
              int n;
              lua_pushvalue(L, 3);
              n = push_captures(ms, s, e);
              lua_call(L, n, 1);
              break;
          }
          case LUA_TTABLE:
          {
              push_onecapture(ms, 0, s, e);
              lua_gettable(L, 3);
              break;
          }
      }
      if (!lua_toboolean(L, -1))
      { /* nil or false? */
          lua_pop(L, 1);
          lua_pushlstring(L, s, e - s); /* keep original text */
      }
      else if (!lua_isstring(L, -1))
          luaL_error(L, "invalid replacement value (a %s)", luaL_typename(L, -1));
      luaL_addvalue(b); /* add result to accumulator */
  }
  
  static int str_gsub(lua_State *L)
  {
      size_t srcl;
      const char *src = luaL_checklstring(L, 1, &srcl);
      const char *p = luaL_checkstring(L, 2);
      int tr = lua_type(L, 3);
      int max_s = luaL_optint(L, 4, srcl + 1);
      int anchor = (*p == '^') ? (p++, 1) : 0;
      int n = 0;
      MatchState ms;
      luaL_Buffer b;
      luaL_argcheck(
          L,
          tr == LUA_TNUMBER || tr == LUA_TSTRING || tr == LUA_TFUNCTION || tr == LUA_TTABLE || tr == LUA_TLIGHTFUNCTION,
          3, "string/function/table/lightfunction expected");
      luaL_buffinit(L, &b);
      ms.L = L;
      ms.src_init = src;
      ms.src_end = src + srcl;
      while (n < max_s)
      {
          const char *e;
          ms.level = 0;
          e = match(&ms, src, p);
          if (e)
          {
              n++;
              add_value(&ms, &b, src, e);
          }
          if (e && e > src) /* non empty match? */
              src = e;      /* skip it */
          else if (src < ms.src_end)
              luaL_addchar(&b, *src++);
          else
              break;
          if (anchor)
              break;
      }
      luaL_addlstring(&b, src, ms.src_end - src);
      luaL_pushresult(&b);
      lua_pushinteger(L, n); /* number of substitutions */
      return 2;
  }
  
  /* }====================================================== */
  
  /* maximum size of each formatted item (> len(format('%99.99f', -1e308))) */
  /* was 512, modified to 128 for eLua */
  #define MAX_ITEM 128
  /* valid flags in a format specification */
  #define FLAGS "-+ #0"
  /*
  ** maximum size of each format specification (such as '%-099.99d')
  ** (+10 accounts for %99.99x plus margin of error)
  */
  #define MAX_FORMAT (sizeof(FLAGS) + sizeof(LUA_INTFRMLEN) + 10)
  
  static void addquoted(lua_State *L, luaL_Buffer *b, int arg)
  {
      size_t l;
      const char *s = luaL_checklstring(L, arg, &l);
      luaL_addchar(b, '"');
      while (l--)
      {
          switch (*s)
          {
              case '"':
              case '\\':
              case '\n':
              {
                  luaL_addchar(b, '\\');
                  luaL_addchar(b, *s);
                  break;
              }
              case '\r':
              {
                  luaL_addlstring(b, "\\r", 2);
                  break;
              }
              case '\0':
              {
                  luaL_addlstring(b, "\\000", 4);
                  break;
              }
              default:
              {
                  luaL_addchar(b, *s);
                  break;
              }
          }
          s++;
      }
      luaL_addchar(b, '"');
  }
  
  static const char *scanformat(lua_State *L, const char *strfrmt, char *form)
  {
      const char *p = strfrmt;
      while (*p != '\0' && strchr(FLAGS, *p) != NULL) p++; /* skip flags */
      if ((size_t)(p - strfrmt) >= sizeof(FLAGS))
          luaL_error(L, "invalid format (repeated flags)");
      if (isdigit(uchar(*p)))
          p++; /* skip width */
      if (isdigit(uchar(*p)))
          p++; /* (2 digits at most) */
      if (*p == '.')
      {
          p++;
          if (isdigit(uchar(*p)))
              p++; /* skip precision */
          if (isdigit(uchar(*p)))
              p++; /* (2 digits at most) */
      }
      if (isdigit(uchar(*p)))
          luaL_error(L, "invalid format (width or precision too long)");
      *(form++) = '%';
      strncpy(form, strfrmt, p - strfrmt + 1);
      form += p - strfrmt + 1;
      *form = '\0';
      return p;
  }
  
  static void addintlen(char *form)
  {
      size_t l = strlen(form);
      char spec = form[l - 1];
      strcpy(form + l - 1, LUA_INTFRMLEN);
      form[l + sizeof(LUA_INTFRMLEN) - 2] = spec;
      form[l + sizeof(LUA_INTFRMLEN) - 1] = '\0';
  }
  
  static int str_format(lua_State *L)
  {
      int top = lua_gettop(L);
      int arg = 1;
      size_t sfl;
      const char *strfrmt = luaL_checklstring(L, arg, &sfl);
      const char *strfrmt_end = strfrmt + sfl;
      luaL_Buffer b;
      luaL_buffinit(L, &b);
      while (strfrmt < strfrmt_end)
      {
          if (*strfrmt != L_ESC)
              luaL_addchar(&b, *strfrmt++);
          else if (*++strfrmt == L_ESC)
              luaL_addchar(&b, *strfrmt++); /* %% */
          else
          {                          /* format item */
              char form[MAX_FORMAT]; /* to store the format (`%...') */
              char buff[MAX_ITEM];   /* to store the formatted item */
              if (++arg > top)
                  luaL_argerror(L, arg, "no value");
              strfrmt = scanformat(L, strfrmt, form);
              switch (*strfrmt++)
              {
                  case 'c':
                  {
                      sprintf(buff, form, (int)luaL_checknumber(L, arg));
                      break;
                  }
                  case 'd':
                  case 'i':
                  {
                      addintlen(form);
                      sprintf(buff, form, (LUA_INTFRM_T)luaL_checknumber(L, arg));
                      break;
                  }
                  case 'o':
                  case 'u':
                  case 'x':
                  case 'X':
                  {
                      addintlen(form);
                      sprintf(buff, form, (unsigned LUA_INTFRM_T)luaL_checknumber(L, arg));
                      break;
                  }
  #if !defined LUA_NUMBER_INTEGRAL
                  case 'e':
                  case 'E':
                  case 'f':
                  case 'g':
                  case 'G':
                  {
                      sprintf(buff, form, (double)luaL_checknumber(L, arg));
                      break;
                  }
  #endif
                  case 'q':
                  {
                      addquoted(L, &b, arg);
                      continue; /* skip the 'addsize' at the end */
                  }
                  case 's':
                  {
                      size_t l;
                      const char *s = luaL_checklstring(L, arg, &l);
                      if (!strchr(form, '.') && l >= 100)
                      {
                          /* no precision and string is too long to be formatted;
                             keep original string */
                          lua_pushvalue(L, arg);
                          luaL_addvalue(&b);
                          continue; /* skip the `addsize' at the end */
                      }
                      else
                      {
                          sprintf(buff, form, s);
                          break;
                      }
                  }
                  default:
                  { /* also treat cases `pnLlh' */
                      return luaL_error(L, "invalid option " LUA_QL("%%%c") " to " LUA_QL("format"), *(strfrmt - 1));
                  }
              }
              luaL_addlstring(&b, buff, strlen(buff));
          }
      }
      luaL_pushresult(&b);
      return 1;
  }
  
  #undef MIN_OPT_LEVEL
  #define MIN_OPT_LEVEL 1
  #include "lrodefs.h"
  const LUA_REG_TYPE strlib[] = {{LSTRKEY("byte"), LFUNCVAL(str_byte)},
                                 {LSTRKEY("char"), LFUNCVAL(str_char)},
                                 {LSTRKEY("dump"), LFUNCVAL(str_dump)},
                                 {LSTRKEY("find"), LFUNCVAL(str_find)},
                                 {LSTRKEY("format"), LFUNCVAL(str_format)},
  #if LUA_OPTIMIZE_MEMORY > 0 && defined(LUA_COMPAT_GFIND)
                                 {LSTRKEY("gfind"), LFUNCVAL(gmatch)},
  #else
                                 {LSTRKEY("gfind"), LFUNCVAL(gfind_nodef)},
  #endif
                                 {LSTRKEY("gmatch"), LFUNCVAL(gmatch)},
                                 {LSTRKEY("gsub"), LFUNCVAL(str_gsub)},
                                 {LSTRKEY("len"), LFUNCVAL(str_len)},
                                 {LSTRKEY("lower"), LFUNCVAL(str_lower)},
                                 {LSTRKEY("match"), LFUNCVAL(str_match)},
                                 {LSTRKEY("rep"), LFUNCVAL(str_rep)},
                                 {LSTRKEY("reverse"), LFUNCVAL(str_reverse)},
                                 {LSTRKEY("sub"), LFUNCVAL(str_sub)},
                                 {LSTRKEY("upper"), LFUNCVAL(str_upper)},
  #if LUA_OPTIMIZE_MEMORY > 0
                                 {LSTRKEY("__index"), LROVAL(strlib)},
  #endif
                                 {LNILKEY, LNILVAL}};
  
  #if LUA_OPTIMIZE_MEMORY != 2
  static void createmetatable(lua_State *L)
  {
      lua_createtable(L, 0, 1); /* create metatable for strings */
      lua_pushliteral(L, "");   /* dummy string */
      lua_pushvalue(L, -2);
      lua_setmetatable(L, -2);        /* set string metatable */
      lua_pop(L, 1);                  /* pop dummy string */
      lua_pushvalue(L, -2);           /* string library... */
      lua_setfield(L, -2, "__index"); /* ...is the __index metamethod */
      lua_pop(L, 1);                  /* pop metatable */
  }
  #endif
  
  /*
  ** Open string library
  */
  LUALIB_API int luaopen_string(lua_State *L)
  {
  #if LUA_OPTIMIZE_MEMORY == 0
      luaL_register(L, LUA_STRLIBNAME, strlib);
  #if defined(LUA_COMPAT_GFIND)
      lua_getfield(L, -1, "gmatch");
      lua_setfield(L, -2, "gfind");
  #endif
      createmetatable(L);
      return 1;
  #else
      lua_pushliteral(L, "");
      lua_pushrotable(L, (void *)strlib);
      lua_setmetatable(L, -2);
      lua_pop(L, 1);
      return 0;
  #endif
  }
  