text: /*
  ** $Id: lstrlib.c,v 1.254.1.1 2017/04/19 17:29:57 roberto Exp $
  ** Standard library for string operations and pattern-matching
  ** See Copyright Notice in lua.h
  */
  
  #define lstrlib_c
  #define LUA_LIB
  
  #include "lprefix.h"
  
  
  #include <ctype.h>
  #include <float.h>
  #include <limits.h>
  #include <locale.h>
  #include <stddef.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  
  #include "lua.h"
  
  #include "lauxlib.h"
  #include "lualib.h"
  
  
  /*
  ** maximum number of captures that a pattern can do during
  ** pattern-matching. This limit is arbitrary, but must fit in
  ** an unsigned char.
  */
  #if !defined(LUA_MAXCAPTURES)
  #define LUA_MAXCAPTURES		32
  #endif
  
  
  /* macro to 'unsign' a character */
  #define uchar(c)	((unsigned char)(c))
  
  
  /*
  ** Some sizes are better limited to fit in 'int', but must also fit in
  ** 'size_t'. (We assume that 'lua_Integer' cannot be smaller than 'int'.)
  */
  #define MAX_SIZET	((size_t)(~(size_t)0))
  
  #define MAXSIZE  \
  	(sizeof(size_t) < sizeof(int) ? MAX_SIZET : (size_t)(INT_MAX))
  
  
  
  
  static int str_len (lua_State *L) {
    size_t l;
    luaL_checklstring(L, 1, &l);
    lua_pushinteger(L, (lua_Integer)l);
    return 1;
  }
  
  
  /* translate a relative string position: negative means back from end */
  static lua_Integer posrelat (lua_Integer pos, size_t len) {
    if (pos >= 0) return pos;
    else if (0u - (size_t)pos > len) return 0;
    else return (lua_Integer)len + pos + 1;
  }
  
  
  static int str_sub (lua_State *L) {
    size_t l;
    const char *s = luaL_checklstring(L, 1, &l);
    lua_Integer start = posrelat(luaL_checkinteger(L, 2), l);
    lua_Integer end = posrelat(luaL_optinteger(L, 3, -1), l);
    if (start < 1) start = 1;
    if (end > (lua_Integer)l) end = l;
    if (start <= end)
      lua_pushlstring(L, s + start - 1, (size_t)(end - start) + 1);
    else lua_pushliteral(L, "");
    return 1;
  }
  
  
  static int str_reverse (lua_State *L) {
    size_t l, i;
    luaL_Buffer b;
    const char *s = luaL_checklstring(L, 1, &l);
    char *p = luaL_buffinitsize(L, &b, l);
    for (i = 0; i < l; i++)
      p[i] = s[l - i - 1];
    luaL_pushresultsize(&b, l);
    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);
    char *p = luaL_buffinitsize(L, &b, l);
    for (i=0; i<l; i++)
      p[i] = tolower(uchar(s[i]));
    luaL_pushresultsize(&b, l);
    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);
    char *p = luaL_buffinitsize(L, &b, l);
    for (i=0; i<l; i++)
      p[i] = toupper(uchar(s[i]));
    luaL_pushresultsize(&b, l);
    return 1;
  }
  
  
  static int str_rep (lua_State *L) {
    size_t l, lsep;
    const char *s = luaL_checklstring(L, 1, &l);
    lua_Integer n = luaL_checkinteger(L, 2);
    const char *sep = luaL_optlstring(L, 3, "", &lsep);
    if (n <= 0) lua_pushliteral(L, "");
    else if (l + lsep < l || l + lsep > MAXSIZE / n)  /* may overflow? */
      return luaL_error(L, "resulting string too large");
    else {
      size_t totallen = (size_t)n * l + (size_t)(n - 1) * lsep;
      luaL_Buffer b;
      char *p = luaL_buffinitsize(L, &b, totallen);
      while (n-- > 1) {  /* first n-1 copies (followed by separator) */
        memcpy(p, s, l * sizeof(char)); p += l;
        if (lsep > 0) {  /* empty 'memcpy' is not that cheap */
          memcpy(p, sep, lsep * sizeof(char));
          p += lsep;
        }
      }
      memcpy(p, s, l * sizeof(char));  /* last copy (not followed by separator) */
      luaL_pushresultsize(&b, totallen);
    }
    return 1;
  }
  
  
  static int str_byte (lua_State *L) {
    size_t l;
    const char *s = luaL_checklstring(L, 1, &l);
    lua_Integer posi = posrelat(luaL_optinteger(L, 2, 1), l);
    lua_Integer pose = posrelat(luaL_optinteger(L, 3, posi), l);
    int n, i;
    if (posi < 1) posi = 1;
    if (pose > (lua_Integer)l) pose = l;
    if (posi > pose) return 0;  /* empty interval; return no values */
    if (pose - posi >= INT_MAX)  /* arithmetic overflow? */
      return luaL_error(L, "string slice too long");
    n = (int)(pose -  posi) + 1;
    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;
    char *p = luaL_buffinitsize(L, &b, n);
    for (i=1; i<=n; i++) {
      lua_Integer c = luaL_checkinteger(L, i);
      luaL_argcheck(L, uchar(c) == c, i, "value out of range");
      p[i - 1] = uchar(c);
    }
    luaL_pushresultsize(&b, n);
    return 1;
  }
  
  #if defined(LUA_USE_LINUX) || defined(LUA_USE_WINDOWS) || defined(LUA_USE_MACOSX)
  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;
    int strip = lua_toboolean(L, 2);
    luaL_checktype(L, 1, LUA_TFUNCTION);
    lua_settop(L, 1);
    luaL_buffinit(L,&b);
    if (lua_dump(L, writer, &b, strip) != 0)
      return luaL_error(L, "unable to dump given function");
    luaL_pushresult(&b);
    return 1;
  }
  #endif
  
  
  /*
  ** {======================================================
  ** 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 */
    const char *p_end;  /* end ('\0') of pattern */
    lua_State *L;
    int matchdepth;  /* control for recursive depth (to avoid C stack overflow) */
    unsigned char level;  /* total number of captures (finished or unfinished) */
    struct {
      const char *init;
      ptrdiff_t len;
    } capture[LUA_MAXCAPTURES];
  } MatchState;
  
  
  /* recursive function */
  static const char *match (MatchState *ms, const char *s, const char *p);
  
  
  /* maximum recursion depth for 'match' */
  #if !defined(MAXCCALLS)
  #define MAXCCALLS	200
  #endif
  
  
  #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 %%%d", l + 1);
    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 == ms->p_end)
          luaL_error(ms->L, "malformed pattern (ends with '%%')");
        return p+1;
      }
      case '[': {
        if (*p == '^') p++;
        do {  /* look for a ']' */
          if (p == ms->p_end)
            luaL_error(ms->L, "malformed pattern (missing ']')");
          if (*(p++) == L_ESC && p < ms->p_end)
            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 'g' : res = isgraph(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;  /* deprecated option */
      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 (MatchState *ms, const char *s, const char *p,
                          const char *ep) {
    if (s >= ms->src_end)
      return 0;
    else {
      int c = uchar(*s);
      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 *matchbalance (MatchState *ms, const char *s,
                                     const char *p) {
    if (p >= ms->p_end - 1)
      luaL_error(ms->L, "malformed pattern (missing arguments to '%%b')");
    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 (singlematch(ms, 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 (singlematch(ms, 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) {
    if (ms->matchdepth-- == 0)
      luaL_error(ms->L, "pattern too complex");
    init: /* using goto's to optimize tail recursion */
    if (p != ms->p_end) {  /* end of pattern? */
      switch (*p) {
        case '(': {  /* start capture */
          if (*(p + 1) == ')')  /* position capture? */
            s = start_capture(ms, s, p + 2, CAP_POSITION);
          else
            s = start_capture(ms, s, p + 1, CAP_UNFINISHED);
          break;
        }
        case ')': {  /* end capture */
          s = end_capture(ms, s, p + 1);
          break;
        }
        case '$': {
          if ((p + 1) != ms->p_end)  /* is the '$' the last char in pattern? */
            goto dflt;  /* no; go to default */
          s = (s == ms->src_end) ? s : NULL;  /* check end of string */
          break;
        }
        case L_ESC: {  /* escaped sequences not in the format class[*+?-]? */
          switch (*(p + 1)) {
            case 'b': {  /* balanced string? */
              s = matchbalance(ms, s, p + 2);
              if (s != NULL) {
                p += 4; goto init;  /* return match(ms, s, p + 4); */
              }  /* else fail (s == NULL) */
              break;
            }
            case 'f': {  /* frontier? */
              const char *ep; char previous;
              p += 2;
              if (*p != '[')
                luaL_error(ms->L, "missing '[' after '%%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)) {
                p = ep; goto init;  /* return match(ms, s, ep); */
              }
              s = NULL;  /* match failed */
              break;
            }
            case '0': case '1': case '2': case '3':
            case '4': case '5': case '6': case '7':
            case '8': case '9': {  /* capture results (%0-%9)? */
              s = match_capture(ms, s, uchar(*(p + 1)));
              if (s != NULL) {
                p += 2; goto init;  /* return match(ms, s, p + 2) */
              }
              break;
            }
            default: goto dflt;
          }
          break;
        }
        default: dflt: {  /* pattern class plus optional suffix */
          const char *ep = classend(ms, p);  /* points to optional suffix */
          /* does not match at least once? */
          if (!singlematch(ms, s, p, ep)) {
            if (*ep == '*' || *ep == '?' || *ep == '-') {  /* accept empty? */
              p = ep + 1; goto init;  /* return match(ms, s, ep + 1); */
            }
            else  /* '+' or no suffix */
              s = NULL;  /* fail */
          }
          else {  /* matched once */
            switch (*ep) {  /* handle optional suffix */
              case '?': {  /* optional */
                const char *res;
                if ((res = match(ms, s + 1, ep + 1)) != NULL)
                  s = res;
                else {
                  p = ep + 1; goto init;  /* else return match(ms, s, ep + 1); */
                }
                break;
              }
              case '+':  /* 1 or more repetitions */
                s++;  /* 1 match already done */
                /* FALLTHROUGH */
              case '*':  /* 0 or more repetitions */
                s = max_expand(ms, s, p, ep);
                break;
              case '-':  /* 0 or more repetitions (minimum) */
                s = min_expand(ms, s, p, ep);
                break;
              default:  /* no suffix */
                s++; p = ep; goto init;  /* return match(ms, s + 1, ep); */
            }
          }
          break;
        }
      }
    }
    ms->matchdepth++;
    return s;
  }
  
  
  
  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 %%%d", i + 1);
    }
    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 */
  }
  
  
  /* check whether pattern has no special characters */
  static int nospecials (const char *p, size_t l) {
    size_t upto = 0;
    do {
      if (strpbrk(p + upto, SPECIALS))
        return 0;  /* pattern has a special character */
      upto += strlen(p + upto) + 1;  /* may have more after \0 */
    } while (upto <= l);
    return 1;  /* no special chars found */
  }
  
  
  static void prepstate (MatchState *ms, lua_State *L,
                         const char *s, size_t ls, const char *p, size_t lp) {
    ms->L = L;
    ms->matchdepth = MAXCCALLS;
    ms->src_init = s;
    ms->src_end = s + ls;
    ms->p_end = p + lp;
  }
  
  
  static void reprepstate (MatchState *ms) {
    ms->level = 0;
    lua_assert(ms->matchdepth == MAXCCALLS);
  }
  
  
  static int str_find_aux (lua_State *L, int find) {
    size_t ls, lp;
    const char *s = luaL_checklstring(L, 1, &ls);
    const char *p = luaL_checklstring(L, 2, &lp);
    lua_Integer init = posrelat(luaL_optinteger(L, 3, 1), ls);
    if (init < 1) init = 1;
    else if (init > (lua_Integer)ls + 1) {  /* start after string's end? */
      lua_pushnil(L);  /* cannot find anything */
      return 1;
    }
    /* explicit request or no special characters? */
    if (find && (lua_toboolean(L, 4) || nospecials(p, lp))) {
      /* do a plain search */
      const char *s2 = lmemfind(s + init - 1, ls - (size_t)init + 1, p, lp);
      if (s2) {
        lua_pushinteger(L, (s2 - s) + 1);
        lua_pushinteger(L, (s2 - s) + lp);
        return 2;
      }
    }
    else {
      MatchState ms;
      const char *s1 = s + init - 1;
      int anchor = (*p == '^');
      if (anchor) {
        p++; lp--;  /* skip anchor character */
      }
      prepstate(&ms, L, s, ls, p, lp);
      do {
        const char *res;
        reprepstate(&ms);
        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);
  }
  
  
  /* state for 'gmatch' */
  typedef struct GMatchState {
    const char *src;  /* current position */
    const char *p;  /* pattern */
    const char *lastmatch;  /* end of last match */
    MatchState ms;  /* match state */
  } GMatchState;
  
  
  static int gmatch_aux (lua_State *L) {
    GMatchState *gm = (GMatchState *)lua_touserdata(L, lua_upvalueindex(3));
    const char *src;
    gm->ms.L = L;
    for (src = gm->src; src <= gm->ms.src_end; src++) {
      const char *e;
      reprepstate(&gm->ms);
      if ((e = match(&gm->ms, src, gm->p)) != NULL && e != gm->lastmatch) {
        gm->src = gm->lastmatch = e;
        return push_captures(&gm->ms, src, e);
      }
    }
    return 0;  /* not found */
  }
  
  
  static int gmatch (lua_State *L) {
    size_t ls, lp;
    const char *s = luaL_checklstring(L, 1, &ls);
    const char *p = luaL_checklstring(L, 2, &lp);
    GMatchState *gm;
    lua_settop(L, 2);  /* keep them on closure to avoid being collected */
    gm = (GMatchState *)lua_newuserdata(L, sizeof(GMatchState));
    prepstate(&gm->ms, L, s, ls, p, lp);
    gm->src = s; gm->p = p; gm->lastmatch = NULL;
    lua_pushcclosure(L, gmatch_aux, 3);
    return 1;
  }
  
  
  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]))) {
          if (news[i] != L_ESC)
            luaL_error(L, "invalid use of '%c' in replacement string", L_ESC);
          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, int tr) {
    lua_State *L = ms->L;
    switch (tr) {
      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;
      }
      default: {  /* LUA_TNUMBER or LUA_TSTRING */
        add_s(ms, b, s, e);
        return;
      }
    }
    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, lp;
    const char *src = luaL_checklstring(L, 1, &srcl);  /* subject */
    const char *p = luaL_checklstring(L, 2, &lp);  /* pattern */
    const char *lastmatch = NULL;  /* end of last match */
    int tr = lua_type(L, 3);  /* replacement type */
    lua_Integer max_s = luaL_optinteger(L, 4, srcl + 1);  /* max replacements */
    int anchor = (*p == '^');
    lua_Integer n = 0;  /* replacement count */
    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);
    if (anchor) {
      p++; lp--;  /* skip anchor character */
    }
    prepstate(&ms, L, src, srcl, p, lp);
    while (n < max_s) {
      const char *e;
      reprepstate(&ms);  /* (re)prepare state for new match */
      if ((e = match(&ms, src, p)) != NULL && e != lastmatch) {  /* match? */
        n++;
        add_value(&ms, &b, src, e, tr);  /* add replacement to buffer */
        src = lastmatch = e;
      }
      else if (src < ms.src_end)  /* otherwise, skip one character */
        luaL_addchar(&b, *src++);
      else break;  /* end of subject */
      if (anchor) break;
    }
    luaL_addlstring(&b, src, ms.src_end-src);
    luaL_pushresult(&b);
    lua_pushinteger(L, n);  /* number of substitutions */
    return 2;
  }
  
  /* }====================================================== */
  
  
  
  /*
  ** {======================================================
  ** STRING FORMAT
  ** =======================================================
  */
  
  #if !defined(lua_number2strx)	/* { */
  
  /*
  ** Hexadecimal floating-point formatter
  */
  
  #include <math.h>
  
  #define SIZELENMOD	(sizeof(LUA_NUMBER_FRMLEN)/sizeof(char))
  
  
  /*
  ** Number of bits that goes into the first digit. It can be any value
  ** between 1 and 4; the following definition tries to align the number
  ** to nibble boundaries by making what is left after that first digit a
  ** multiple of 4.
  */
  #define L_NBFD		((l_mathlim(MANT_DIG) - 1)%4 + 1)
  
  
  /*
  ** Add integer part of 'x' to buffer and return new 'x'
  */
  static lua_Number adddigit (char *buff, int n, lua_Number x) {
    lua_Number dd = l_mathop(floor)(x);  /* get integer part from 'x' */
    int d = (int)dd;
    buff[n] = (d < 10 ? d + '0' : d - 10 + 'a');  /* add to buffer */
    return x - dd;  /* return what is left */
  }
  
  
  static int num2straux (char *buff, int sz, lua_Number x) {
    /* if 'inf' or 'NaN', format it like '%g' */
    if (x != x || x == (lua_Number)HUGE_VAL || x == -(lua_Number)HUGE_VAL)
      return l_sprintf(buff, sz, LUA_NUMBER_FMT, (LUAI_UACNUMBER)x);
    else if (x == 0) {  /* can be -0... */
      /* create "0" or "-0" followed by exponent */
      return l_sprintf(buff, sz, LUA_NUMBER_FMT "x0p+0", (LUAI_UACNUMBER)x);
    }
    else {
      int e;
      lua_Number m = l_mathop(frexp)(x, &e);  /* 'x' fraction and exponent */
      int n = 0;  /* character count */
      if (m < 0) {  /* is number negative? */
        buff[n++] = '-';  /* add signal */
        m = -m;  /* make it positive */
      }
      buff[n++] = '0'; buff[n++] = 'x';  /* add "0x" */
      m = adddigit(buff, n++, m * (1 << L_NBFD));  /* add first digit */
      e -= L_NBFD;  /* this digit goes before the radix point */
      if (m > 0) {  /* more digits? */
        buff[n++] = lua_getlocaledecpoint();  /* add radix point */
        do {  /* add as many digits as needed */
          m = adddigit(buff, n++, m * 16);
        } while (m > 0);
      }
      n += l_sprintf(buff + n, sz - n, "p%+d", e);  /* add exponent */
      lua_assert(n < sz);
      return n;
    }
  }
  
  
  static int lua_number2strx (lua_State *L, char *buff, int sz,
                              const char *fmt, lua_Number x) {
    int n = num2straux(buff, sz, x);
    if (fmt[SIZELENMOD] == 'A') {
      int i;
      for (i = 0; i < n; i++)
        buff[i] = toupper(uchar(buff[i]));
    }
    else if (fmt[SIZELENMOD] != 'a')
      return luaL_error(L, "modifiers for format '%%a'/'%%A' not implemented");
    return n;
  }
  
  #endif				/* } */
  
  
  /*
  ** Maximum size of each formatted item. This maximum size is produced
  ** by format('%.99f', -maxfloat), and is equal to 99 + 3 ('-', '.',
  ** and '\0') + number of decimal digits to represent maxfloat (which
  ** is maximum exponent + 1). (99+3+1 then rounded to 120 for "extra
  ** expenses", such as locale-dependent stuff)
  */
  #define MAX_ITEM        (120 + l_mathlim(MAX_10_EXP))
  
  
  /* valid flags in a format specification */
  #define FLAGS	"-+ #0"
  
  /*
  ** maximum size of each format specification (such as "%-099.99d")
  */
  #define MAX_FORMAT	32
  
  
  static void addquoted (luaL_Buffer *b, const char *s, size_t len) {
    luaL_addchar(b, '"');
    while (len--) {
      if (*s == '"' || *s == '\\' || *s == '\n') {
        luaL_addchar(b, '\\');
        luaL_addchar(b, *s);
      }
      else if (iscntrl(uchar(*s))) {
        char buff[10];
        if (!isdigit(uchar(*(s+1))))
          l_sprintf(buff, sizeof(buff), "\\%d", (int)uchar(*s));
        else
          l_sprintf(buff, sizeof(buff), "\\%03d", (int)uchar(*s));
        luaL_addstring(b, buff);
      }
      else
        luaL_addchar(b, *s);
      s++;
    }
    luaL_addchar(b, '"');
  }
  
  
  /*
  ** Ensures the 'buff' string uses a dot as the radix character.
  */
  static void checkdp (char *buff, int nb) {
    if (memchr(buff, '.', nb) == NULL) {  /* no dot? */
      char point = lua_getlocaledecpoint();  /* try locale point */
      char *ppoint = (char *)memchr(buff, point, nb);
      if (ppoint) *ppoint = '.';  /* change it to a dot */
    }
  }
  
  
  static void addliteral (lua_State *L, luaL_Buffer *b, int arg) {
    switch (lua_type(L, arg)) {
      case LUA_TSTRING: {
        size_t len;
        const char *s = lua_tolstring(L, arg, &len);
        addquoted(b, s, len);
        break;
      }
      case LUA_TNUMBER: {
        char *buff = luaL_prepbuffsize(b, MAX_ITEM);
        int nb;
        if (!lua_isinteger(L, arg)) {  /* float? */
          lua_Number n = lua_tonumber(L, arg);  /* write as hexa ('%a') */
          nb = lua_number2strx(L, buff, MAX_ITEM, "%" LUA_NUMBER_FRMLEN "a", n);
          checkdp(buff, nb);  /* ensure it uses a dot */
        }
        else {  /* integers */
          lua_Integer n = lua_tointeger(L, arg);
          const char *format = (n == LUA_MININTEGER)  /* corner case? */
                             ? "0x%" LUA_INTEGER_FRMLEN "x"  /* use hexa */
                             : LUA_INTEGER_FMT;  /* else use default format */
          nb = l_sprintf(buff, MAX_ITEM, format, (LUAI_UACINT)n);
        }
        luaL_addsize(b, nb);
        break;
      }
      case LUA_TNIL: case LUA_TBOOLEAN: {
        luaL_tolstring(L, arg, NULL);
        luaL_addvalue(b);
        break;
      }
      default: {
        luaL_argerror(L, arg, "value has no literal form");
      }
    }
  }
  
  
  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)/sizeof(char))
      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++) = '%';
    memcpy(form, strfrmt, ((p - strfrmt) + 1) * sizeof(char));
    form += (p - strfrmt) + 1;
    *form = '\0';
    return p;
  }
  
  
  /*
  ** add length modifier into formats
  */
  static void addlenmod (char *form, const char *lenmod) {
    size_t l = strlen(form);
    size_t lm = strlen(lenmod);
    char spec = form[l - 1];
    strcpy(form + l - 1, lenmod);
    form[l + lm - 1] = spec;
    form[l + lm] = '\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 = luaL_prepbuffsize(&b, MAX_ITEM);  /* to put formatted item */
        int nb = 0;  /* number of bytes in added item */
        if (++arg > top)
          luaL_argerror(L, arg, "no value");
        strfrmt = scanformat(L, strfrmt, form);
        switch (*strfrmt++) {
          case 'c': {
            nb = l_sprintf(buff, MAX_ITEM, form, (int)luaL_checkinteger(L, arg));
            break;
          }
          case 'd': case 'i':
          case 'o': case 'u': case 'x': case 'X': {
            lua_Integer n = luaL_checkinteger(L, arg);
            addlenmod(form, LUA_INTEGER_FRMLEN);
            nb = l_sprintf(buff, MAX_ITEM, form, (LUAI_UACINT)n);
            break;
          }
          case 'a': case 'A':
            addlenmod(form, LUA_NUMBER_FRMLEN);
            nb = lua_number2strx(L, buff, MAX_ITEM, form,
                                    luaL_checknumber(L, arg));
            break;
          case 'e': case 'E': case 'f':
          case 'g': case 'G': {
            lua_Number n = luaL_checknumber(L, arg);
            addlenmod(form, LUA_NUMBER_FRMLEN);
            nb = l_sprintf(buff, MAX_ITEM, form, (LUAI_UACNUMBER)n);
            break;
          }
          case 'q': {
            addliteral(L, &b, arg);
            break;
          }
          case 's': {
            size_t l;
            const char *s = luaL_tolstring(L, arg, &l);
            if (form[2] == '\0')  /* no modifiers? */
              luaL_addvalue(&b);  /* keep entire string */
            else {
              luaL_argcheck(L, l == strlen(s), arg, "string contains zeros");
              if (!strchr(form, '.') && l >= 100) {
                /* no precision and string is too long to be formatted */
                luaL_addvalue(&b);  /* keep entire string */
              }
              else {  /* format the string into 'buff' */
                nb = l_sprintf(buff, MAX_ITEM, form, s);
                lua_pop(L, 1);  /* remove result from 'luaL_tolstring' */
              }
            }
            break;
          }
          default: {  /* also treat cases 'pnLlh' */
            return luaL_error(L, "invalid option '%%%c' to 'format'",
                                 *(strfrmt - 1));
          }
        }
        lua_assert(nb < MAX_ITEM);
        luaL_addsize(&b, nb);
      }
    }
    luaL_pushresult(&b);
    return 1;
  }
  
  /* }====================================================== */
  
  
  /*
  ** {======================================================
  ** PACK/UNPACK
  ** =======================================================
  */
  
  
  /* value used for padding */
  #if !defined(LUAL_PACKPADBYTE)
  #define LUAL_PACKPADBYTE		0x00
  #endif
  
  /* maximum size for the binary representation of an integer */
  #define MAXINTSIZE	16
  
  /* number of bits in a character */
  #define NB	CHAR_BIT
  
  /* mask for one character (NB 1's) */
  #define MC	((1 << NB) - 1)
  
  /* size of a lua_Integer */
  #define SZINT	((int)sizeof(lua_Integer))
  
  
  /* dummy union to get native endianness */
  static const union {
    int dummy;
    char little;  /* true iff machine is little endian */
  } nativeendian = {1};
  
  
  /* dummy structure to get native alignment requirements */
  struct cD {
    char c;
    union { double d; void *p; lua_Integer i; lua_Number n; } u;
  };
  
  #define MAXALIGN	(offsetof(struct cD, u))
  
  
  /*
  ** Union for serializing floats
  */
  typedef union Ftypes {
    float f;
    double d;
    lua_Number n;
    char buff[5 * sizeof(lua_Number)];  /* enough for any float type */
  } Ftypes;
  
  
  /*
  ** information to pack/unpack stuff
  */
  typedef struct Header {
    lua_State *L;
    int islittle;
    int maxalign;
  } Header;
  
  
  /*
  ** options for pack/unpack
  */
  typedef enum KOption {
    Kint,		/* signed integers */
    Kuint,	/* unsigned integers */
    Kfloat,	/* floating-point numbers */
    Kchar,	/* fixed-length strings */
    Kstring,	/* strings with prefixed length */
    Kzstr,	/* zero-terminated strings */
    Kpadding,	/* padding */
    Kpaddalign,	/* padding for alignment */
    Knop		/* no-op (configuration or spaces) */
  } KOption;
  
  
  /*
  ** Read an integer numeral from string 'fmt' or return 'df' if
  ** there is no numeral
  */
  static int digit (int c) { return '0' <= c && c <= '9'; }
  
  static int getnum (const char **fmt, int df) {
    if (!digit(**fmt))  /* no number? */
      return df;  /* return default value */
    else {
      int a = 0;
      do {
        a = a*10 + (*((*fmt)++) - '0');
      } while (digit(**fmt) && a <= ((int)MAXSIZE - 9)/10);
      return a;
    }
  }
  
  
  /*
  ** Read an integer numeral and raises an error if it is larger
  ** than the maximum size for integers.
  */
  static int getnumlimit (Header *h, const char **fmt, int df) {
    int sz = getnum(fmt, df);
    if (sz > MAXINTSIZE || sz <= 0)
      return luaL_error(h->L, "integral size (%d) out of limits [1,%d]",
                              sz, MAXINTSIZE);
    return sz;
  }
  
  
  /*
  ** Initialize Header
  */
  static void initheader (lua_State *L, Header *h) {
    h->L = L;
    h->islittle = nativeendian.little;
    h->maxalign = 1;
  }
  
  
  /*
  ** Read and classify next option. 'size' is filled with option's size.
  */
  static KOption getoption (Header *h, const char **fmt, int *size) {
    int opt = *((*fmt)++);
    *size = 0;  /* default */
    switch (opt) {
      case 'b': *size = sizeof(char); return Kint;
      case 'B': *size = sizeof(char); return Kuint;
      case 'h': *size = sizeof(short); return Kint;
      case 'H': *size = sizeof(short); return Kuint;
      case 'l': *size = sizeof(long); return Kint;
      case 'L': *size = sizeof(long); return Kuint;
      case 'j': *size = sizeof(lua_Integer); return Kint;
      case 'J': *size = sizeof(lua_Integer); return Kuint;
      case 'T': *size = sizeof(size_t); return Kuint;
      case 'f': *size = sizeof(float); return Kfloat;
      case 'd': *size = sizeof(double); return Kfloat;
      case 'n': *size = sizeof(lua_Number); return Kfloat;
      case 'i': *size = getnumlimit(h, fmt, sizeof(int)); return Kint;
      case 'I': *size = getnumlimit(h, fmt, sizeof(int)); return Kuint;
      case 's': *size = getnumlimit(h, fmt, sizeof(size_t)); return Kstring;
      case 'c':
        *size = getnum(fmt, -1);
        if (*size == -1)
          luaL_error(h->L, "missing size for format option 'c'");
        return Kchar;
      case 'z': return Kzstr;
      case 'x': *size = 1; return Kpadding;
      case 'X': return Kpaddalign;
      case ' ': break;
      case '<': h->islittle = 1; break;
      case '>': h->islittle = 0; break;
      case '=': h->islittle = nativeendian.little; break;
      case '!': h->maxalign = getnumlimit(h, fmt, MAXALIGN); break;
      default: luaL_error(h->L, "invalid format option '%c'", opt);
    }
    return Knop;
  }
  
  
  /*
  ** Read, classify, and fill other details about the next option.
  ** 'psize' is filled with option's size, 'notoalign' with its
  ** alignment requirements.
  ** Local variable 'size' gets the size to be aligned. (Kpadal option
  ** always gets its full alignment, other options are limited by
  ** the maximum alignment ('maxalign'). Kchar option needs no alignment
  ** despite its size.
  */
  static KOption getdetails (Header *h, size_t totalsize,
                             const char **fmt, int *psize, int *ntoalign) {
    KOption opt = getoption(h, fmt, psize);
    int align = *psize;  /* usually, alignment follows size */
    if (opt == Kpaddalign) {  /* 'X' gets alignment from following option */
      if (**fmt == '\0' || getoption(h, fmt, &align) == Kchar || align == 0)
        luaL_argerror(h->L, 1, "invalid next option for option 'X'");
    }
    if (align <= 1 || opt == Kchar)  /* need no alignment? */
      *ntoalign = 0;
    else {
      if (align > h->maxalign)  /* enforce maximum alignment */
        align = h->maxalign;
      if ((align & (align - 1)) != 0)  /* is 'align' not a power of 2? */
        luaL_argerror(h->L, 1, "format asks for alignment not power of 2");
      *ntoalign = (align - (int)(totalsize & (align - 1))) & (align - 1);
    }
    return opt;
  }
  
  
  /*
  ** Pack integer 'n' with 'size' bytes and 'islittle' endianness.
  ** The final 'if' handles the case when 'size' is larger than
  ** the size of a Lua integer, correcting the extra sign-extension
  ** bytes if necessary (by default they would be zeros).
  */
  static void packint (luaL_Buffer *b, lua_Unsigned n,
                       int islittle, int size, int neg) {
    char *buff = luaL_prepbuffsize(b, size);
    int i;
    buff[islittle ? 0 : size - 1] = (char)(n & MC);  /* first byte */
    for (i = 1; i < size; i++) {
      n >>= NB;
      buff[islittle ? i : size - 1 - i] = (char)(n & MC);
    }
    if (neg && size > SZINT) {  /* negative number need sign extension? */
      for (i = SZINT; i < size; i++)  /* correct extra bytes */
        buff[islittle ? i : size - 1 - i] = (char)MC;
    }
    luaL_addsize(b, size);  /* add result to buffer */
  }
  
  
  /*
  ** Copy 'size' bytes from 'src' to 'dest', correcting endianness if
  ** given 'islittle' is different from native endianness.
  */
  static void copywithendian (volatile char *dest, volatile const char *src,
                              int size, int islittle) {
    if (islittle == nativeendian.little) {
      while (size-- != 0)
        *(dest++) = *(src++);
    }
    else {
      dest += size - 1;
      while (size-- != 0)
        *(dest--) = *(src++);
    }
  }
  
  
  static int str_pack (lua_State *L) {
    luaL_Buffer b;
    Header h;
    const char *fmt = luaL_checkstring(L, 1);  /* format string */
    int arg = 1;  /* current argument to pack */
    size_t totalsize = 0;  /* accumulate total size of result */
    initheader(L, &h);
    lua_pushnil(L);  /* mark to separate arguments from string buffer */
    luaL_buffinit(L, &b);
    while (*fmt != '\0') {
      int size, ntoalign;
      KOption opt = getdetails(&h, totalsize, &fmt, &size, &ntoalign);
      totalsize += ntoalign + size;
      while (ntoalign-- > 0)
       luaL_addchar(&b, LUAL_PACKPADBYTE);  /* fill alignment */
      arg++;
      switch (opt) {
        case Kint: {  /* signed integers */
          lua_Integer n = luaL_checkinteger(L, arg);
          if (size < SZINT) {  /* need overflow check? */
            lua_Integer lim = (lua_Integer)1 << ((size * NB) - 1);
            luaL_argcheck(L, -lim <= n && n < lim, arg, "integer overflow");
          }
          packint(&b, (lua_Unsigned)n, h.islittle, size, (n < 0));
          break;
        }
        case Kuint: {  /* unsigned integers */
          lua_Integer n = luaL_checkinteger(L, arg);
          if (size < SZINT)  /* need overflow check? */
            luaL_argcheck(L, (lua_Unsigned)n < ((lua_Unsigned)1 << (size * NB)),
                             arg, "unsigned overflow");
          packint(&b, (lua_Unsigned)n, h.islittle, size, 0);
          break;
        }
        case Kfloat: {  /* floating-point options */
          volatile Ftypes u;
          char *buff = luaL_prepbuffsize(&b, size);
          lua_Number n = luaL_checknumber(L, arg);  /* get argument */
          if (size == sizeof(u.f)) u.f = (float)n;  /* copy it into 'u' */
          else if (size == sizeof(u.d)) u.d = (double)n;
          else u.n = n;
          /* move 'u' to final result, correcting endianness if needed */
          copywithendian(buff, u.buff, size, h.islittle);
          luaL_addsize(&b, size);
          break;
        }
        case Kchar: {  /* fixed-size string */
          size_t len;
          const char *s = luaL_checklstring(L, arg, &len);
          luaL_argcheck(L, len <= (size_t)size, arg,
                           "string longer than given size");
          luaL_addlstring(&b, s, len);  /* add string */
          while (len++ < (size_t)size)  /* pad extra space */
            luaL_addchar(&b, LUAL_PACKPADBYTE);
          break;
        }
        case Kstring: {  /* strings with length count */
          size_t len;
          const char *s = luaL_checklstring(L, arg, &len);
          luaL_argcheck(L, size >= (int)sizeof(size_t) ||
                           len < ((size_t)1 << (size * NB)),
                           arg, "string length does not fit in given size");
          packint(&b, (lua_Unsigned)len, h.islittle, size, 0);  /* pack length */
          luaL_addlstring(&b, s, len);
          totalsize += len;
          break;
        }
        case Kzstr: {  /* zero-terminated string */
          size_t len;
          const char *s = luaL_checklstring(L, arg, &len);
          luaL_argcheck(L, strlen(s) == len, arg, "string contains zeros");
          luaL_addlstring(&b, s, len);
          luaL_addchar(&b, '\0');  /* add zero at the end */
          totalsize += len + 1;
          break;
        }
        case Kpadding: luaL_addchar(&b, LUAL_PACKPADBYTE);  /* FALLTHROUGH */
        case Kpaddalign: case Knop:
          arg--;  /* undo increment */
          break;
      }
    }
    luaL_pushresult(&b);
    return 1;
  }
  
  
  static int str_packsize (lua_State *L) {
    Header h;
    const char *fmt = luaL_checkstring(L, 1);  /* format string */
    size_t totalsize = 0;  /* accumulate total size of result */
    initheader(L, &h);
    while (*fmt != '\0') {
      int size, ntoalign;
      KOption opt = getdetails(&h, totalsize, &fmt, &size, &ntoalign);
      size += ntoalign;  /* total space used by option */
      luaL_argcheck(L, totalsize <= MAXSIZE - size, 1,
                       "format result too large");
      totalsize += size;
      switch (opt) {
        case Kstring:  /* strings with length count */
        case Kzstr:    /* zero-terminated string */
          luaL_argerror(L, 1, "variable-length format");
          /* call never return, but to avoid warnings: *//* FALLTHROUGH */
        default:  break;
      }
    }
    lua_pushinteger(L, (lua_Integer)totalsize);
    return 1;
  }
  
  
  /*
  ** Unpack an integer with 'size' bytes and 'islittle' endianness.
  ** If size is smaller than the size of a Lua integer and integer
  ** is signed, must do sign extension (propagating the sign to the
  ** higher bits); if size is larger than the size of a Lua integer,
  ** it must check the unread bytes to see whether they do not cause an
  ** overflow.
  */
  static lua_Integer unpackint (lua_State *L, const char *str,
                                int islittle, int size, int issigned) {
    lua_Unsigned res = 0;
    int i;
    int limit = (size  <= SZINT) ? size : SZINT;
    for (i = limit - 1; i >= 0; i--) {
      res <<= NB;
      res |= (lua_Unsigned)(unsigned char)str[islittle ? i : size - 1 - i];
    }
    if (size < SZINT) {  /* real size smaller than lua_Integer? */
      if (issigned) {  /* needs sign extension? */
        lua_Unsigned mask = (lua_Unsigned)1 << (size*NB - 1);
        res = ((res ^ mask) - mask);  /* do sign extension */
      }
    }
    else if (size > SZINT) {  /* must check unread bytes */
      int mask = (!issigned || (lua_Integer)res >= 0) ? 0 : MC;
      for (i = limit; i < size; i++) {
        if ((unsigned char)str[islittle ? i : size - 1 - i] != mask)
          luaL_error(L, "%d-byte integer does not fit into Lua Integer", size);
      }
    }
    return (lua_Integer)res;
  }
  
  
  static int str_unpack (lua_State *L) {
    Header h;
    const char *fmt = luaL_checkstring(L, 1);
    size_t ld;
    const char *data = luaL_checklstring(L, 2, &ld);
    size_t pos = (size_t)posrelat(luaL_optinteger(L, 3, 1), ld) - 1;
    int n = 0;  /* number of results */
    luaL_argcheck(L, pos <= ld, 3, "initial position out of string");
    initheader(L, &h);
    while (*fmt != '\0') {
      int size, ntoalign;
      KOption opt = getdetails(&h, pos, &fmt, &size, &ntoalign);
      if ((size_t)ntoalign + size > ~pos || pos + ntoalign + size > ld)
        luaL_argerror(L, 2, "data string too short");
      pos += ntoalign;  /* skip alignment */
      /* stack space for item + next position */
      luaL_checkstack(L, 2, "too many results");
      n++;
      switch (opt) {
        case Kint:
        case Kuint: {
          lua_Integer res = unpackint(L, data + pos, h.islittle, size,
                                         (opt == Kint));
          lua_pushinteger(L, res);
          break;
        }
        case Kfloat: {
          volatile Ftypes u;
          lua_Number num;
          copywithendian(u.buff, data + pos, size, h.islittle);
          if (size == sizeof(u.f)) num = (lua_Number)u.f;
          else if (size == sizeof(u.d)) num = (lua_Number)u.d;
          else num = u.n;
          lua_pushnumber(L, num);
          break;
        }
        case Kchar: {
          lua_pushlstring(L, data + pos, size);
          break;
        }
        case Kstring: {
          size_t len = (size_t)unpackint(L, data + pos, h.islittle, size, 0);
          luaL_argcheck(L, pos + len + size <= ld, 2, "data string too short");
          lua_pushlstring(L, data + pos + size, len);
          pos += len;  /* skip string */
          break;
        }
        case Kzstr: {
          size_t len = (int)strlen(data + pos);
          lua_pushlstring(L, data + pos, len);
          pos += len + 1;  /* skip string plus final '\0' */
          break;
        }
        case Kpaddalign: case Kpadding: case Knop:
          n--;  /* undo increment */
          break;
      }
      pos += size;
    }
    lua_pushinteger(L, pos + 1);  /* next position */
    return n + 1;
  }
  
  int l_str_toHex (lua_State *L);
  int l_str_fromHex (lua_State *L);
  int l_str_split (lua_State *L);
  int l_str_toValue (lua_State *L);
  int l_str_urlEncode (lua_State *L);
  int l_str_toBase64(lua_State *L);
  int l_str_fromBase64(lua_State *L);
  int l_str_toBase32(lua_State *L);
  int l_str_fromBase32(lua_State *L);
  int l_str_startsWith(lua_State *L);
  int l_str_endsWith(lua_State *L);
  int l_str_strs(lua_State *L);
  int l_str_trim(lua_State *L);
  //-----------------------------------------------------------
  
  #include "rotable2.h"
  static const rotable_Reg_t strlib[] = {
    {"byte", ROREG_FUNC(str_byte)},
    {"char", ROREG_FUNC(str_char)},
  #if defined(LUA_USE_LINUX) || defined(LUA_USE_WINDOWS) || defined(LUA_USE_MACOSX)
    {"dump", ROREG_FUNC(str_dump)},
  #endif
    {"find", ROREG_FUNC(str_find)},
    {"format", ROREG_FUNC(str_format)},
    {"gmatch", ROREG_FUNC(gmatch)},
    {"gsub", ROREG_FUNC(str_gsub)},
    {"len", ROREG_FUNC(str_len)},
    {"lower", ROREG_FUNC(str_lower)},
    {"match", ROREG_FUNC(str_match)},
    {"rep", ROREG_FUNC(str_rep)},
    {"reverse", ROREG_FUNC(str_reverse)},
    {"sub", ROREG_FUNC(str_sub)},
    {"upper", ROREG_FUNC(str_upper)},
    {"pack", ROREG_FUNC(str_pack)},
    {"packsize", ROREG_FUNC(str_packsize)},
    {"unpack", ROREG_FUNC(str_unpack)},
    //-----------------------------
    // 添加几个常用的方法
    {"toHex", ROREG_FUNC(l_str_toHex)},
    {"fromHex", ROREG_FUNC(l_str_fromHex)},
    {"split", ROREG_FUNC(l_str_split)},
    {"toValue", ROREG_FUNC(l_str_toValue)},
    {"urlEncode", ROREG_FUNC(l_str_urlEncode)},
    {"fromBase64", ROREG_FUNC(l_str_fromBase64)},
    {"toBase64", ROREG_FUNC(l_str_toBase64)},
    {"fromBase32", ROREG_FUNC(l_str_fromBase32)},
    {"toBase32", ROREG_FUNC(l_str_toBase32)},
  
    {"startsWith", ROREG_FUNC(l_str_startsWith)},
    {"endsWith", ROREG_FUNC(l_str_endsWith)},
    {"trim",     ROREG_FUNC(l_str_trim)},
  #if defined(LUA_USE_LINUX) || defined(LUA_USE_WINDOWS) || defined(LUA_USE_MACOSX)
    {"strs", ROREG_FUNC(l_str_strs)},
  #endif
    //{"urlDecode", str_urlDecode},
    //-----------------------------
    {NULL, ROREG_INT(0) }
  };
  
  
  static void createmetatable (lua_State *L) {
    lua_createtable(L, 0, 1);  /* table to be metatable for strings */
    lua_pushliteral(L, "");  /* dummy string */
    lua_pushvalue(L, -2);  /* copy table */
    lua_setmetatable(L, -2);  /* set table as metatable for strings */
    lua_pop(L, 1);  /* pop dummy string */
    rotable2_newidx(L, strlib);
    lua_setfield(L, -2, "__index");  /* metatable.__index = string */
    lua_pop(L, 1);  /* pop metatable */
  }
  
  
  /*
  ** Open string library
  */
  LUAMOD_API int luaopen_string (lua_State *L) {
    luat_newlib2(L, strlib);
    createmetatable(L);
    return 1;
  }
  
  