misc/liblua/lstrlib.c
author unc0rr
Sun, 02 Dec 2012 01:25:11 +0400
changeset 8178 8bd087478b48
parent 3697 d5b30d6373fc
child 10017 de822cd3df3a
permissions -rw-r--r--
Fix QSettings problems: - Reopen file in ReadOnly mode if it was open in ReadWrite mode and is being read. This is needed for stupid QSettings which opens file in ReadWrite mode just to call readAll() on it. - Implement setSize(0)

/*
** $Id: lstrlib.c,v 1.132.1.4 2008/07/11 17:27:21 roberto Exp $
** Standard library for string operations and pattern-matching
** See Copyright Notice in lua.h
*/


#include <ctype.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define lstrlib_c
#define LUA_LIB

#include "lua.h"

#include "lauxlib.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;
}


static int gfind_nodef (lua_State *L) {
  return luaL_error(L, LUA_QL("string.gfind") " was renamed to "
                       LUA_QL("string.gmatch"));
}


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: {
      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, 3,
                      "string/function/table 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))) */
#define MAX_ITEM	512
/* 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 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 */
      arg++;
      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;
        }
        case 'e':  case 'E': case 'f':
        case 'g': case 'G': {
          sprintf(buff, form, (double)luaL_checknumber(L, arg));
          break;
        }
        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;
}


static const luaL_Reg strlib[] = {
  {"byte", str_byte},
  {"char", str_char},
  {"dump", str_dump},
  {"find", str_find},
  {"format", str_format},
  {"gfind", gfind_nodef},
  {"gmatch", gmatch},
  {"gsub", str_gsub},
  {"len", str_len},
  {"lower", str_lower},
  {"match", str_match},
  {"rep", str_rep},
  {"reverse", str_reverse},
  {"sub", str_sub},
  {"upper", str_upper},
  {NULL, NULL}
};


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 */
}


/*
** Open string library
*/
LUALIB_API int luaopen_string (lua_State *L) {
  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;
}