text: /*
  ** $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 "mln_lua.h"
  
  #include "mln_lauxlib.h"
  #include "mln_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;
    lua_State *L = ms->L;
    const char *news = lua_tolstring(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_tolstring(L, -1, NULL);  /* if number, convert it to string */
          lua_remove(L, -2);  /* remove original value */
          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_tolstring(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_tolstring(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;
  }
  
  