lstrlib.c - external/github.com/lua/lua - Git at Google

 /*
 ** $Id: lstrlib.c,v 1.86 2002/06/25 19:16:44 roberto Exp roberto $
 ** 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>

 #include "lua.h"

 #include "lauxlib.h"
 #include "lualib.h"


 /* macro to `unsign' a character */
 #ifndef uchar
 #define uchar(c)        ((unsigned char)(c))
 #endif


 typedef long sint32;	/* a signed version for size_t */


 static int str_len (lua_State *L) {
   size_t l;
   luaL_check_lstr(L, 1, &l);
   lua_pushnumber(L, l);
   return 1;
 }


 static sint32 posrelat (sint32 pos, size_t len) {
   /* relative string position: negative means back from end */
   return (pos>=0) ? pos : (sint32)len+pos+1;
 }


 static int str_sub (lua_State *L) {
   size_t l;
   const char *s = luaL_check_lstr(L, 1, &l);
   sint32 start = posrelat(luaL_check_long(L, 2), l);
   sint32 end = posrelat(luaL_opt_long(L, 3, -1), l);
   if (start < 1) start = 1;
   if (end > (sint32)l) end = l;
   if (start <= end)
     lua_pushlstring(L, s+start-1, end-start+1);
   else lua_pushliteral(L, "");
   return 1;
 }


 static int str_lower (lua_State *L) {
   size_t l;
   size_t i;
   luaL_Buffer b;
   const char *s = luaL_check_lstr(L, 1, &l);
   luaL_buffinit(L, &b);
   for (i=0; i<l; i++)
     luaL_putchar(&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_check_lstr(L, 1, &l);
   luaL_buffinit(L, &b);
   for (i=0; i<l; i++)
     luaL_putchar(&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_check_lstr(L, 1, &l);
   int n = luaL_check_int(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_check_lstr(L, 1, &l);
   sint32 pos = posrelat(luaL_opt_long(L, 2, 1), l);
   luaL_arg_check(L, 0 < pos && (size_t)(pos) <= l, 2,  "out of range");
   lua_pushnumber(L, uchar(s[pos-1]));
   return 1;
 }


 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_check_int(L, i);
     luaL_arg_check(L, uchar(c) == c, i, "invalid value");
     luaL_putchar(&b, uchar(c));
   }
   luaL_pushresult(&b);
   return 1;
 }


 /*
 ** {======================================================
 ** PATTERN MATCHING
 ** =======================================================
 */

 #ifndef MAX_CAPTURES
 #define MAX_CAPTURES 32  /* arbitrary limit */
 #endif


 #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;
     sint32 len;
   } capture[MAX_CAPTURES];
 } MatchState;


 #define 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 *luaI_classend (MatchState *ms, const char *p) {
   switch (*p++) {
     case ESC:
       if (*p == '\0')
         luaL_error(ms->L, "malformed pattern (ends with `%')");
       return p+1;
     case '[':
       if (*p == '^') p++;
       do {  /* look for a `]' */
         if (*p == '\0')
           luaL_error(ms->L, "malformed pattern (missing `]')");
         if (*(p++) == 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 == ESC) {
       p++;
       if (match_class(c, *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 luaI_singlematch (int c, const char *p, const char *ep) {
   switch (*p) {
     case '.':  /* matches any char */
       return 1;
     case ESC:
       return match_class(c, *(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) {
   sint32 i = 0;  /* counts maximum expand for item */
   while ((s+i)<ms->src_end && luaI_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 && luaI_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 >= MAX_CAPTURES) 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 ESC:  /* may be %[0-9] or %b */
       if (isdigit(uchar(*(p+1)))) {  /* capture? */
         s = match_capture(ms, s, *(p+1));
         if (s == NULL) return NULL;
         p+=2; goto init;  /* else return match(ms, s, p+2) */
       }
       else if (*(p+1) == '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); */
       }
       else 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 = luaI_classend(ms, p);  /* points to what is next */
       int m = s<ms->src_end && luaI_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) {
   int l = ms->capture[i].len;
   if (l == CAP_UNFINISHED) luaL_error(ms->L, "unfinished capture");
   if (l == CAP_POSITION)
     lua_pushnumber(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;
   luaL_check_stack(ms->L, ms->level, "too many captures");
   if (ms->level == 0 && s) {  /* no explicit captures? */
     lua_pushlstring(ms->L, s, e-s);  /* return whole match */
     return 1;
   }
   else {  /* return all captures */
     for (i=0; i<ms->level; i++)
       push_onecapture(ms, i);
     return ms->level;  /* number of strings pushed */
   }
 }


 static int str_find (lua_State *L) {
   size_t l1, l2;
   const char *s = luaL_check_lstr(L, 1, &l1);
   const char *p = luaL_check_lstr(L, 2, &l2);
   sint32 init = posrelat(luaL_opt_long(L, 3, 1), l1) - 1;
   luaL_arg_check(L, 0 <= init && (size_t)(init) <= l1, 3, "out of range");
   if (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_pushnumber(L, s2-s+1);
       lua_pushnumber(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) {
         lua_pushnumber(L, s1-s+1);  /* start */
         lua_pushnumber(L, res-s);   /* end */
         return push_captures(&ms, NULL, 0) + 2;
       }
     } while (s1++<ms.src_end && !anchor);
   }
   lua_pushnil(L);  /* not found */
   return 1;
 }


 static int gfind_aux (lua_State *L) {
   MatchState ms;
   const char *s = lua_tostring(L, lua_upvalueindex(1));
   size_t ls = lua_strlen(L, lua_upvalueindex(1));
   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_tonumber(L, lua_upvalueindex(3));
        src <= ms.src_end;
        src++) {
     const char *e;
     ms.level = 0;
     if ((e = match(&ms, src, p)) != NULL) {
       int newstart = e-s;
       if (e == src) newstart++;  /* empty match? go at least one position */
       lua_pushnumber(L, newstart);
       lua_replace(L, lua_upvalueindex(3));
       return push_captures(&ms, src, e);
     }
   }
   return 0;  /* not found */
 }


 static int gfind (lua_State *L) {
   luaL_check_string(L, 1);
   luaL_check_string(L, 2);
   lua_settop(L, 2);
   lua_pushnumber(L, 0);
   lua_pushcclosure(L, gfind_aux, 3);
   return 1;
 }


 static void add_s (MatchState *ms, luaL_Buffer *b,
                    const char *s, const char *e) {
   lua_State *L = ms->L;
   if (lua_isstring(L, 3)) {
     const char *news = lua_tostring(L, 3);
     size_t l = lua_strlen(L, 3);
     size_t i;
     for (i=0; i<l; i++) {
       if (news[i] != ESC)
         luaL_putchar(b, news[i]);
       else {
         i++;  /* skip ESC */
         if (!isdigit(uchar(news[i])))
           luaL_putchar(b, news[i]);
         else {
           int level = check_capture(ms, news[i]);
           push_onecapture(ms, level);
           luaL_addvalue(b);  /* add capture to accumulated result */
         }
       }
     }
   }
   else {  /* is a function */
     int n;
     lua_pushvalue(L, 3);
     n = push_captures(ms, s, e);
     lua_call(L, n, 1);
     if (lua_isstring(L, -1))
       luaL_addvalue(b);  /* add return to accumulated result */
     else
       lua_pop(L, 1);  /* function result is not a string: pop it */
   }
 }


 static int str_gsub (lua_State *L) {
   size_t srcl;
   const char *src = luaL_check_lstr(L, 1, &srcl);
   const char *p = luaL_check_string(L, 2);
   int max_s = luaL_opt_int(L, 4, srcl+1);
   int anchor = (*p == '^') ? (p++, 1) : 0;
   int n = 0;
   MatchState ms;
   luaL_Buffer b;
   luaL_arg_check(L,
     lua_gettop(L) >= 3 && (lua_isstring(L, 3) || lua_isfunction(L, 3)),
     3, "string or function 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_s(&ms, &b, src, e);
     }
     if (e && e>src) /* non empty match? */
       src = e;  /* skip it */
     else if (src < ms.src_end)
       luaL_putchar(&b, *src++);
     else break;
     if (anchor) break;
   }
   luaL_addlstring(&b, src, ms.src_end-src);
   luaL_pushresult(&b);
   lua_pushnumber(L, n);  /* number of substitutions */
   return 2;
 }

 /* }====================================================== */


 /* maximum size of each formatted item (> len(format('%99.99f', -1e308))) */
 #define MAX_ITEM	512
 /* maximum size of each format specification (such as '%-099.99d') */
 #define MAX_FORMAT	20


 static void luaI_addquoted (lua_State *L, luaL_Buffer *b, int arg) {
   size_t l;
   const char *s = luaL_check_lstr(L, arg, &l);
   luaL_putchar(b, '"');
   while (l--) {
     switch (*s) {
       case '"':  case '\\':  case '\n':
         luaL_putchar(b, '\\');
         luaL_putchar(b, *s);
         break;
       case '\0': luaL_addlstring(b, "\\000", 4); break;
       default: luaL_putchar(b, *s);
     }
     s++;
   }
   luaL_putchar(b, '"');
 }


 static const char *scanformat (lua_State *L, const char *strfrmt,
                                  char *form, int *hasprecision) {
   const char *p = strfrmt;
   while (strchr("-+ #0", *p)) p++;  /* skip flags */
   if (isdigit(uchar(*p))) p++;  /* skip width */
   if (isdigit(uchar(*p))) p++;  /* (2 digits at most) */
   if (*p == '.') {
     p++;
     *hasprecision = 1;
     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)");
   if (p-strfrmt+2 > MAX_FORMAT)  /* +2 to include `%' and the specifier */
     luaL_error(L, "invalid format (too long)");
   form[0] = '%';
   strncpy(form+1, strfrmt, p-strfrmt+1);
   form[p-strfrmt+2] = 0;
   return p;
 }


 static int str_format (lua_State *L) {
   int arg = 1;
   size_t sfl;
   const char *strfrmt = luaL_check_lstr(L, arg, &sfl);
   const char *strfrmt_end = strfrmt+sfl;
   luaL_Buffer b;
   luaL_buffinit(L, &b);
   while (strfrmt < strfrmt_end) {
     if (*strfrmt != '%')
       luaL_putchar(&b, *strfrmt++);
     else if (*++strfrmt == '%')
       luaL_putchar(&b, *strfrmt++);  /* %% */
     else { /* format item */
       char form[MAX_FORMAT];  /* to store the format (`%...') */
       char buff[MAX_ITEM];  /* to store the formatted item */
       int hasprecision = 0;
       if (isdigit(uchar(*strfrmt)) && *(strfrmt+1) == '$')
         return luaL_error(L, "obsolete `format' option (d$)");
       arg++;
       strfrmt = scanformat(L, strfrmt, form, &hasprecision);
       switch (*strfrmt++) {
         case 'c':  case 'd':  case 'i':
           sprintf(buff, form, luaL_check_int(L, arg));
           break;
         case 'o':  case 'u':  case 'x':  case 'X':
           sprintf(buff, form, (unsigned int)(luaL_check_number(L, arg)));
           break;
         case 'e':  case 'E': case 'f':
         case 'g': case 'G':
           sprintf(buff, form, luaL_check_number(L, arg));
           break;
         case 'q':
           luaI_addquoted(L, &b, arg);
           continue;  /* skip the `addsize' at the end */
         case 's': {
           size_t l;
           const char *s = luaL_check_lstr(L, arg, &l);
           if (!hasprecision && 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 in `format'");
       }
       luaL_addlstring(&b, buff, strlen(buff));
     }
   }
   luaL_pushresult(&b);
   return 1;
 }


 static const luaL_reg strlib[] = {
   {"len", str_len},
   {"sub", str_sub},
   {"lower", str_lower},
   {"upper", str_upper},
   {"char", str_char},
   {"rep", str_rep},
   {"byte", str_byte},
   {"format", str_format},
   {"find", str_find},
   {"gfind", gfind},
   {"gsub", str_gsub},
   {NULL, NULL}
 };


 /*
 ** Open string library
 */
 LUALIB_API int lua_strlibopen (lua_State *L) {
   luaL_opennamedlib(L, LUA_STRLIBNAME, strlib, 0);
   return 0;
 }
	/*
	** $Id: lstrlib.c,v 1.86 2002/06/25 19:16:44 roberto Exp roberto $
	** 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>

	#include "lua.h"

	#include "lauxlib.h"
	#include "lualib.h"


	/* macro to `unsign' a character */
	#ifndef uchar
	#define uchar(c) ((unsigned char)(c))
	#endif


	typedef long sint32; /* a signed version for size_t */


	static int str_len (lua_State *L) {
	size_t l;
	luaL_check_lstr(L, 1, &l);
	lua_pushnumber(L, l);
	return 1;
	}


	static sint32 posrelat (sint32 pos, size_t len) {
	/* relative string position: negative means back from end */
	return (pos>=0) ? pos : (sint32)len+pos+1;
	}


	static int str_sub (lua_State *L) {
	size_t l;
	const char *s = luaL_check_lstr(L, 1, &l);
	sint32 start = posrelat(luaL_check_long(L, 2), l);
	sint32 end = posrelat(luaL_opt_long(L, 3, -1), l);
	if (start < 1) start = 1;
	if (end > (sint32)l) end = l;
	if (start <= end)
	lua_pushlstring(L, s+start-1, end-start+1);
	else lua_pushliteral(L, "");
	return 1;
	}


	static int str_lower (lua_State *L) {
	size_t l;
	size_t i;
	luaL_Buffer b;
	const char *s = luaL_check_lstr(L, 1, &l);
	luaL_buffinit(L, &b);
	for (i=0; i<l; i++)
	luaL_putchar(&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_check_lstr(L, 1, &l);
	luaL_buffinit(L, &b);
	for (i=0; i<l; i++)
	luaL_putchar(&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_check_lstr(L, 1, &l);
	int n = luaL_check_int(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_check_lstr(L, 1, &l);
	sint32 pos = posrelat(luaL_opt_long(L, 2, 1), l);
	luaL_arg_check(L, 0 < pos && (size_t)(pos) <= l, 2, "out of range");
	lua_pushnumber(L, uchar(s[pos-1]));
	return 1;
	}


	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_check_int(L, i);
	luaL_arg_check(L, uchar(c) == c, i, "invalid value");
	luaL_putchar(&b, uchar(c));
	}
	luaL_pushresult(&b);
	return 1;
	}



	/*
	** {======================================================
	** PATTERN MATCHING
	** =======================================================
	*/

	#ifndef MAX_CAPTURES
	#define MAX_CAPTURES 32 /* arbitrary limit */
	#endif


	#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;
	sint32 len;
	} capture[MAX_CAPTURES];
	} MatchState;


	#define 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 luaI_classend (MatchState ms, const char *p) {
	switch (*p++) {
	case ESC:
	if (*p == '\0')
	luaL_error(ms->L, "malformed pattern (ends with `%')");
	return p+1;
	case '[':
	if (*p == '^') p++;
	do { /* look for a `]' */
	if (*p == '\0')
	luaL_error(ms->L, "malformed pattern (missing `]')");
	if ((p++) == 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 == ESC) {
	p++;
	if (match_class(c, *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 luaI_singlematch (int c, const char p, const char ep) {
	switch (*p) {
	case '.': /* matches any char */
	return 1;
	case ESC:
	return match_class(c, *(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) {
	sint32 i = 0; /* counts maximum expand for item */
	while ((s+i)<ms->src_end && luaI_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 && luaI_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 >= MAX_CAPTURES) 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 ESC: /* may be %[0-9] or %b */
	if (isdigit(uchar((p+1)))) { / capture? */
	s = match_capture(ms, s, *(p+1));
	if (s == NULL) return NULL;
	p+=2; goto init; /* else return match(ms, s, p+2) */
	}
	else if ((p+1) == '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); */
	}
	else 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 = luaI_classend(ms, p); / points to what is next */
	int m = s<ms->src_end && luaI_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) {
	int l = ms->capture[i].len;
	if (l == CAP_UNFINISHED) luaL_error(ms->L, "unfinished capture");
	if (l == CAP_POSITION)
	lua_pushnumber(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;
	luaL_check_stack(ms->L, ms->level, "too many captures");
	if (ms->level == 0 && s) { /* no explicit captures? */
	lua_pushlstring(ms->L, s, e-s); /* return whole match */
	return 1;
	}
	else { /* return all captures */
	for (i=0; i<ms->level; i++)
	push_onecapture(ms, i);
	return ms->level; /* number of strings pushed */
	}
	}


	static int str_find (lua_State *L) {
	size_t l1, l2;
	const char *s = luaL_check_lstr(L, 1, &l1);
	const char *p = luaL_check_lstr(L, 2, &l2);
	sint32 init = posrelat(luaL_opt_long(L, 3, 1), l1) - 1;
	luaL_arg_check(L, 0 <= init && (size_t)(init) <= l1, 3, "out of range");
	if (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_pushnumber(L, s2-s+1);
	lua_pushnumber(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) {
	lua_pushnumber(L, s1-s+1); /* start */
	lua_pushnumber(L, res-s); /* end */
	return push_captures(&ms, NULL, 0) + 2;
	}
	} while (s1++<ms.src_end && !anchor);
	}
	lua_pushnil(L); /* not found */
	return 1;
	}


	static int gfind_aux (lua_State *L) {
	MatchState ms;
	const char *s = lua_tostring(L, lua_upvalueindex(1));
	size_t ls = lua_strlen(L, lua_upvalueindex(1));
	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_tonumber(L, lua_upvalueindex(3));
	src <= ms.src_end;
	src++) {
	const char *e;
	ms.level = 0;
	if ((e = match(&ms, src, p)) != NULL) {
	int newstart = e-s;
	if (e == src) newstart++; /* empty match? go at least one position */
	lua_pushnumber(L, newstart);
	lua_replace(L, lua_upvalueindex(3));
	return push_captures(&ms, src, e);
	}
	}
	return 0; /* not found */
	}


	static int gfind (lua_State *L) {
	luaL_check_string(L, 1);
	luaL_check_string(L, 2);
	lua_settop(L, 2);
	lua_pushnumber(L, 0);
	lua_pushcclosure(L, gfind_aux, 3);
	return 1;
	}


	static void add_s (MatchState ms, luaL_Buffer b,
	const char s, const char e) {
	lua_State *L = ms->L;
	if (lua_isstring(L, 3)) {
	const char *news = lua_tostring(L, 3);
	size_t l = lua_strlen(L, 3);
	size_t i;
	for (i=0; i<l; i++) {
	if (news[i] != ESC)
	luaL_putchar(b, news[i]);
	else {
	i++; /* skip ESC */
	if (!isdigit(uchar(news[i])))
	luaL_putchar(b, news[i]);
	else {
	int level = check_capture(ms, news[i]);
	push_onecapture(ms, level);
	luaL_addvalue(b); /* add capture to accumulated result */
	}
	}
	}
	}
	else { /* is a function */
	int n;
	lua_pushvalue(L, 3);
	n = push_captures(ms, s, e);
	lua_call(L, n, 1);
	if (lua_isstring(L, -1))
	luaL_addvalue(b); /* add return to accumulated result */
	else
	lua_pop(L, 1); /* function result is not a string: pop it */
	}
	}


	static int str_gsub (lua_State *L) {
	size_t srcl;
	const char *src = luaL_check_lstr(L, 1, &srcl);
	const char *p = luaL_check_string(L, 2);
	int max_s = luaL_opt_int(L, 4, srcl+1);
	int anchor = (*p == '^') ? (p++, 1) : 0;
	int n = 0;
	MatchState ms;
	luaL_Buffer b;
	luaL_arg_check(L,
	lua_gettop(L) >= 3 && (lua_isstring(L, 3) \|\| lua_isfunction(L, 3)),
	3, "string or function 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_s(&ms, &b, src, e);
	}
	if (e && e>src) /* non empty match? */
	src = e; /* skip it */
	else if (src < ms.src_end)
	luaL_putchar(&b, *src++);
	else break;
	if (anchor) break;
	}
	luaL_addlstring(&b, src, ms.src_end-src);
	luaL_pushresult(&b);
	lua_pushnumber(L, n); /* number of substitutions */
	return 2;
	}

	/* }====================================================== */


	/* maximum size of each formatted item (> len(format('%99.99f', -1e308))) */
	#define MAX_ITEM 512
	/* maximum size of each format specification (such as '%-099.99d') */
	#define MAX_FORMAT 20


	static void luaI_addquoted (lua_State L, luaL_Buffer b, int arg) {
	size_t l;
	const char *s = luaL_check_lstr(L, arg, &l);
	luaL_putchar(b, '"');
	while (l--) {
	switch (*s) {
	case '"': case '\\': case '\n':
	luaL_putchar(b, '\\');
	luaL_putchar(b, *s);
	break;
	case '\0': luaL_addlstring(b, "\\000", 4); break;
	default: luaL_putchar(b, *s);
	}
	s++;
	}
	luaL_putchar(b, '"');
	}


	static const char scanformat (lua_State L, const char *strfrmt,
	char form, int hasprecision) {
	const char *p = strfrmt;
	while (strchr("-+ #0", p)) p++; / skip flags */
	if (isdigit(uchar(p))) p++; / skip width */
	if (isdigit(uchar(p))) p++; / (2 digits at most) */
	if (*p == '.') {
	p++;
	*hasprecision = 1;
	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)");
	if (p-strfrmt+2 > MAX_FORMAT) /* +2 to include `%' and the specifier */
	luaL_error(L, "invalid format (too long)");
	form[0] = '%';
	strncpy(form+1, strfrmt, p-strfrmt+1);
	form[p-strfrmt+2] = 0;
	return p;
	}


	static int str_format (lua_State *L) {
	int arg = 1;
	size_t sfl;
	const char *strfrmt = luaL_check_lstr(L, arg, &sfl);
	const char *strfrmt_end = strfrmt+sfl;
	luaL_Buffer b;
	luaL_buffinit(L, &b);
	while (strfrmt < strfrmt_end) {
	if (*strfrmt != '%')
	luaL_putchar(&b, *strfrmt++);
	else if (*++strfrmt == '%')
	luaL_putchar(&b, strfrmt++); / %% */
	else { /* format item */
	char form[MAX_FORMAT]; /* to store the format (`%...') */
	char buff[MAX_ITEM]; /* to store the formatted item */
	int hasprecision = 0;
	if (isdigit(uchar(strfrmt)) && (strfrmt+1) == '$')
	return luaL_error(L, "obsolete `format' option (d$)");
	arg++;
	strfrmt = scanformat(L, strfrmt, form, &hasprecision);
	switch (*strfrmt++) {
	case 'c': case 'd': case 'i':
	sprintf(buff, form, luaL_check_int(L, arg));
	break;
	case 'o': case 'u': case 'x': case 'X':
	sprintf(buff, form, (unsigned int)(luaL_check_number(L, arg)));
	break;
	case 'e': case 'E': case 'f':
	case 'g': case 'G':
	sprintf(buff, form, luaL_check_number(L, arg));
	break;
	case 'q':
	luaI_addquoted(L, &b, arg);
	continue; /* skip the `addsize' at the end */
	case 's': {
	size_t l;
	const char *s = luaL_check_lstr(L, arg, &l);
	if (!hasprecision && 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 in `format'");
	}
	luaL_addlstring(&b, buff, strlen(buff));
	}
	}
	luaL_pushresult(&b);
	return 1;
	}


	static const luaL_reg strlib[] = {
	{"len", str_len},
	{"sub", str_sub},
	{"lower", str_lower},
	{"upper", str_upper},
	{"char", str_char},
	{"rep", str_rep},
	{"byte", str_byte},
	{"format", str_format},
	{"find", str_find},
	{"gfind", gfind},
	{"gsub", str_gsub},
	{NULL, NULL}
	};


	/*
	** Open string library
	*/
	LUALIB_API int lua_strlibopen (lua_State *L) {
	luaL_opennamedlib(L, LUA_STRLIBNAME, strlib, 0);
	return 0;
	}