text: /*
  ** String library.
  ** Copyright (C) 2005-2017 Mike Pall. See Copyright Notice in luajit.h
  **
  ** Major portions taken verbatim or adapted from the Lua interpreter.
  ** Copyright (C) 1994-2008 Lua.org, PUC-Rio. See Copyright Notice in lua.h
  */
  
  #include <stdio.h>
  
  #define lib_string_c
  #define LUA_LIB
  
  #include "lua.h"
  #include "lauxlib.h"
  #include "lualib.h"
  
  #include "lj_obj.h"
  #include "lj_gc.h"
  #include "lj_err.h"
  #include "lj_str.h"
  #include "lj_tab.h"
  #include "lj_meta.h"
  #include "lj_state.h"
  #include "lj_ff.h"
  #include "lj_bcdump.h"
  #include "lj_char.h"
  #include "lj_lib.h"
  
  /* ------------------------------------------------------------------------ */
  
  #define LJLIB_MODULE_string
  
  LJLIB_ASM(string_len)		LJLIB_REC(.)
  {
    lj_lib_checkstr(L, 1);
    return FFH_RETRY;
  }
  
  LJLIB_ASM(string_byte)		LJLIB_REC(string_range 0)
  {
    GCstr *s = lj_lib_checkstr(L, 1);
    int32_t len = (int32_t)s->len;
    int32_t start = lj_lib_optint(L, 2, 1);
    int32_t stop = lj_lib_optint(L, 3, start);
    int32_t n, i;
    const unsigned char *p;
    if (stop < 0) stop += len+1;
    if (start < 0) start += len+1;
    if (start <= 0) start = 1;
    if (stop > len) stop = len;
    if (start > stop) return FFH_RES(0);  /* Empty interval: return no results. */
    start--;
    n = stop - start;
    if ((uint32_t)n > LUAI_MAXCSTACK)
      lj_err_caller(L, LJ_ERR_STRSLC);
    lj_state_checkstack(L, (MSize)n);
    p = (const unsigned char *)strdata(s) + start;
    for (i = 0; i < n; i++)
      setintV(L->base + i-1, p[i]);
    return FFH_RES(n);
  }
  
  LJLIB_ASM(string_char)
  {
    int i, nargs = (int)(L->top - L->base);
    char *buf = lj_str_needbuf(L, &G(L)->tmpbuf, (MSize)nargs);
    for (i = 1; i <= nargs; i++) {
      int32_t k = lj_lib_checkint(L, i);
      if (!checku8(k))
        lj_err_arg(L, i, LJ_ERR_BADVAL);
      buf[i-1] = (char)k;
    }
    setstrV(L, L->base-1, lj_str_new(L, buf, (size_t)nargs));
    return FFH_RES(1);
  }
  
  LJLIB_ASM(string_sub)		LJLIB_REC(string_range 1)
  {
    lj_lib_checkstr(L, 1);
    lj_lib_checkint(L, 2);
    setintV(L->base+2, lj_lib_optint(L, 3, -1));
    return FFH_RETRY;
  }
  
  LJLIB_ASM(string_rep)
  {
    GCstr *s = lj_lib_checkstr(L, 1);
    int32_t k = lj_lib_checkint(L, 2);
    GCstr *sep = lj_lib_optstr(L, 3);
    int32_t len = (int32_t)s->len;
    global_State *g = G(L);
    int64_t tlen;
    const char *src;
    char *buf;
    if (k <= 0) {
    empty:
      setstrV(L, L->base-1, &g->strempty);
      return FFH_RES(1);
    }
    if (sep) {
      tlen = (int64_t)len + sep->len;
      if (tlen > LJ_MAX_STR)
        lj_err_caller(L, LJ_ERR_STROV);
      tlen *= k;
      if (tlen > LJ_MAX_STR)
        lj_err_caller(L, LJ_ERR_STROV);
    } else {
      tlen = (int64_t)k * len;
      if (tlen > LJ_MAX_STR)
        lj_err_caller(L, LJ_ERR_STROV);
    }
    if (tlen == 0) goto empty;
    buf = lj_str_needbuf(L, &g->tmpbuf, (MSize)tlen);
    src = strdata(s);
    if (sep) {
      tlen -= sep->len;  /* Ignore trailing separator. */
      if (k > 1) {  /* Paste one string and one separator. */
        int32_t i;
        i = 0; while (i < len) *buf++ = src[i++];
        src = strdata(sep); len = sep->len;
        i = 0; while (i < len) *buf++ = src[i++];
        src = g->tmpbuf.buf; len += s->len; k--;  /* Now copy that k-1 times. */
      }
    }
    do {
      int32_t i = 0;
      do { *buf++ = src[i++]; } while (i < len);
    } while (--k > 0);
    setstrV(L, L->base-1, lj_str_new(L, g->tmpbuf.buf, (size_t)tlen));
    return FFH_RES(1);
  }
  
  LJLIB_ASM(string_reverse)
  {
    GCstr *s = lj_lib_checkstr(L, 1);
    lj_str_needbuf(L, &G(L)->tmpbuf, s->len);
    return FFH_RETRY;
  }
  LJLIB_ASM_(string_lower)
  LJLIB_ASM_(string_upper)
  
  /* ------------------------------------------------------------------------ */
  
  static int writer_buf(lua_State *L, const void *p, size_t size, void *b)
  {
    luaL_addlstring((luaL_Buffer *)b, (const char *)p, size);
    UNUSED(L);
    return 0;
  }
  
  LJLIB_CF(string_dump)
  {
    GCfunc *fn = lj_lib_checkfunc(L, 1);
    int strip = L->base+1 < L->top && tvistruecond(L->base+1);
    luaL_Buffer b;
    L->top = L->base+1;
    luaL_buffinit(L, &b);
    if (!isluafunc(fn) || lj_bcwrite(L, funcproto(fn), writer_buf, &b, strip))
      lj_err_caller(L, LJ_ERR_STRDUMP);
    luaL_pushresult(&b);
    return 1;
  }
  
  /* ------------------------------------------------------------------------ */
  
  /* macro to `unsign' a character */
  #define uchar(c)        ((unsigned char)(c))
  
  #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) */
    int depth;
    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)
      lj_err_caller(ms->L, LJ_ERR_STRCAPI);
    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;
    lj_err_caller(ms->L, LJ_ERR_STRPATC);
    return 0;  /* unreachable */
  }
  
  static const char *classend(MatchState *ms, const char *p)
  {
    switch (*p++) {
    case L_ESC:
      if (*p == '\0')
        lj_err_caller(ms->L, LJ_ERR_STRPATE);
      return p+1;
    case '[':
      if (*p == '^') p++;
      do {  /* look for a `]' */
        if (*p == '\0')
  	lj_err_caller(ms->L, LJ_ERR_STRPATM);
        if (*(p++) == L_ESC && *p != '\0')
  	p++;  /* skip escapes (e.g. `%]') */
      } while (*p != ']');
      return p+1;
    default:
      return p;
    }
  }
  
  static const unsigned char match_class_map[32] = {
    0,LJ_CHAR_ALPHA,0,LJ_CHAR_CNTRL,LJ_CHAR_DIGIT,0,0,LJ_CHAR_GRAPH,0,0,0,0,
    LJ_CHAR_LOWER,0,0,0,LJ_CHAR_PUNCT,0,0,LJ_CHAR_SPACE,0,
    LJ_CHAR_UPPER,0,LJ_CHAR_ALNUM,LJ_CHAR_XDIGIT,0,0,0,0,0,0,0
  };
  
  static int match_class(int c, int cl)
  {
    if ((cl & 0xc0) == 0x40) {
      int t = match_class_map[(cl&0x1f)];
      if (t) {
        t = lj_char_isa(c, t);
        return (cl & 0x20) ? t : !t;
      }
      if (cl == 'z') return c == 0;
      if (cl == 'Z') return c != 0;
    }
    return (cl == c);
  }
  
  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)
      lj_err_caller(ms->L, LJ_ERR_STRPATU);
    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) lj_err_caller(ms->L, LJ_ERR_STRCAPN);
    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 = (size_t)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->depth > LJ_MAX_XLEVEL)
      lj_err_caller(ms->L, LJ_ERR_STRPATX);
    init: /* using goto's to optimize tail recursion */
    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 L_ESC:
      switch (*(p+1)) {
      case 'b':  /* balanced string? */
        s = matchbalance(ms, s, p+2);
        if (s == NULL) break;
        p+=4;
        goto init;  /* else s = match(ms, s, p+4); */
      case 'f': {  /* frontier? */
        const char *ep; char previous;
        p += 2;
        if (*p != '[')
  	lj_err_caller(ms->L, LJ_ERR_STRPATB);
        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)) { s = NULL; break; }
        p=ep;
        goto init;  /* else s = match(ms, s, ep); */
        }
      default:
        if (lj_char_isdigit(uchar(*(p+1)))) {  /* capture results (%0-%9)? */
  	s = match_capture(ms, s, uchar(*(p+1)));
  	if (s == NULL) break;
  	p+=2;
  	goto init;  /* else s = match(ms, s, p+2) */
        }
        goto dflt;  /* case default */
      }
      break;
    case '\0':  /* end of pattern */
      break;  /* match succeeded */
    case '$':
      /* is the `$' the last char in pattern? */
      if (*(p+1) != '\0') goto dflt;
      if (s != ms->src_end) s = NULL;  /* check end of string */
      break;
    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)) {
  	s = res;
  	break;
        }
        p=ep+1;
        goto init;  /* else s = match(ms, s, ep+1); */
        }
      case '*':  /* 0 or more repetitions */
        s = max_expand(ms, s, p, ep);
        break;
      case '+':  /* 1 or more repetitions */
        s = (m ? max_expand(ms, s+1, p, ep) : NULL);
        break;
      case '-':  /* 0 or more repetitions (minimum) */
        s = min_expand(ms, s, p, ep);
        break;
      default:
        if (m) { s++; p=ep; goto init; }  /* else s = match(ms, s+1, ep); */
        s = NULL;
        break;
      }
      break;
      }
    }
    ms->depth--;
    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 -= (size_t)(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, (size_t)(e - s));  /* add whole match */
      else
        lj_err_caller(ms->L, LJ_ERR_STRCAPI);
    } else {
      ptrdiff_t l = ms->capture[i].len;
      if (l == CAP_UNFINISHED) lj_err_caller(ms->L, LJ_ERR_STRCAPU);
      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, (size_t)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 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_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) {
  #if LJ_52
      setnilV(L->top-1);
      return 1;
  #else
      init = (ptrdiff_t)l1;
  #endif
    }
    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-(size_t)init, p, l2);
      if (s2) {
        lua_pushinteger(L, s2-s+1);
        lua_pushinteger(L, s2-s+(ptrdiff_t)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 = ms.depth = 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;
  }
  
  LJLIB_CF(string_find)
  {
    return str_find_aux(L, 1);
  }
  
  LJLIB_CF(string_match)
  {
    return str_find_aux(L, 0);
  }
  
  LJLIB_NOREG LJLIB_CF(string_gmatch_aux)
  {
    const char *p = strVdata(lj_lib_upvalue(L, 2));
    GCstr *str = strV(lj_lib_upvalue(L, 1));
    const char *s = strdata(str);
    TValue *tvpos = lj_lib_upvalue(L, 3);
    const char *src = s + tvpos->u32.lo;
    MatchState ms;
    ms.L = L;
    ms.src_init = s;
    ms.src_end = s + str->len;
    for (; src <= ms.src_end; src++) {
      const char *e;
      ms.level = ms.depth = 0;
      if ((e = match(&ms, src, p)) != NULL) {
        int32_t pos = (int32_t)(e - s);
        if (e == src) pos++;  /* Ensure progress for empty match. */
        tvpos->u32.lo = (uint32_t)pos;
        return push_captures(&ms, src, e);
      }
    }
    return 0;  /* not found */
  }
  
  LJLIB_CF(string_gmatch)
  {
    lj_lib_checkstr(L, 1);
    lj_lib_checkstr(L, 2);
    L->top = L->base+3;
    (L->top-1)->u64 = 0;
    lj_lib_pushcc(L, lj_cf_string_gmatch_aux, FF_string_gmatch_aux, 3);
    return 1;
  }
  
  static void add_s(MatchState *ms, luaL_Buffer *b, const char *s, const char *e)
  {
    size_t l, i;
    const char *news = lua_tolstring(ms->L, 3, &l);
    for (i = 0; i < l; i++) {
      if (news[i] != L_ESC) {
        luaL_addchar(b, news[i]);
      } else {
        i++;  /* skip ESC */
        if (!lj_char_isdigit(uchar(news[i]))) {
  	luaL_addchar(b, news[i]);
        } else if (news[i] == '0') {
  	luaL_addlstring(b, s, (size_t)(e - s));
        } else {
  	push_onecapture(ms, news[i] - '1', s, e);
  	luaL_addvalue(b);  /* add capture to accumulated result */
        }
      }
    }
  }
  
  static void add_value(MatchState *ms, luaL_Buffer *b,
  		      const char *s, const char *e)
  {
    lua_State *L = ms->L;
    switch (lua_type(L, 3)) {
      case LUA_TNUMBER:
      case LUA_TSTRING: {
        add_s(ms, b, s, e);
        return;
      }
      case LUA_TFUNCTION: {
        int n;
        lua_pushvalue(L, 3);
        n = push_captures(ms, s, e);
        lua_call(L, n, 1);
        break;
      }
      case LUA_TTABLE: {
        push_onecapture(ms, 0, s, e);
        lua_gettable(L, 3);
        break;
      }
    }
    if (!lua_toboolean(L, -1)) {  /* nil or false? */
      lua_pop(L, 1);
      lua_pushlstring(L, s, (size_t)(e - s));  /* keep original text */
    } else if (!lua_isstring(L, -1)) {
      lj_err_callerv(L, LJ_ERR_STRGSRV, luaL_typename(L, -1));
    }
    luaL_addvalue(b);  /* add result to accumulator */
  }
  
  LJLIB_CF(string_gsub)
  {
    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, (int)(srcl+1));
    int anchor = (*p == '^') ? (p++, 1) : 0;
    int n = 0;
    MatchState ms;
    luaL_Buffer b;
    if (!(tr == LUA_TNUMBER || tr == LUA_TSTRING ||
  	tr == LUA_TFUNCTION || tr == LUA_TTABLE))
      lj_err_arg(L, 3, LJ_ERR_NOSFT);
    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 = ms.depth = 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, (size_t)(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_FMTITEM	512
  /* valid flags in a format specification */
  #define FMT_FLAGS	"-+ #0"
  /*
  ** maximum size of each format specification (such as '%-099.99d')
  ** (+10 accounts for %99.99x plus margin of error)
  */
  #define MAX_FMTSPEC	(sizeof(FMT_FLAGS) + sizeof(LUA_INTFRMLEN) + 10)
  
  static void addquoted(lua_State *L, luaL_Buffer *b, int arg)
  {
    GCstr *str = lj_lib_checkstr(L, arg);
    int32_t len = (int32_t)str->len;
    const char *s = strdata(str);
    luaL_addchar(b, '"');
    while (len--) {
      uint32_t c = uchar(*s);
      if (c == '"' || c == '\\' || c == '\n') {
        luaL_addchar(b, '\\');
      } else if (lj_char_iscntrl(c)) {  /* This can only be 0-31 or 127. */
        uint32_t d;
        luaL_addchar(b, '\\');
        if (c >= 100 || lj_char_isdigit(uchar(s[1]))) {
  	luaL_addchar(b, '0'+(c >= 100)); if (c >= 100) c -= 100;
  	goto tens;
        } else if (c >= 10) {
        tens:
  	d = (c * 205) >> 11; c -= d * 10; luaL_addchar(b, '0'+d);
        }
        c += '0';
      }
      luaL_addchar(b, c);
      s++;
    }
    luaL_addchar(b, '"');
  }
  
  static const char *scanformat(lua_State *L, const char *strfrmt, char *form)
  {
    const char *p = strfrmt;
    while (*p != '\0' && strchr(FMT_FLAGS, *p) != NULL) p++;  /* skip flags */
    if ((size_t)(p - strfrmt) >= sizeof(FMT_FLAGS))
      lj_err_caller(L, LJ_ERR_STRFMTR);
    if (lj_char_isdigit(uchar(*p))) p++;  /* skip width */
    if (lj_char_isdigit(uchar(*p))) p++;  /* (2 digits at most) */
    if (*p == '.') {
      p++;
      if (lj_char_isdigit(uchar(*p))) p++;  /* skip precision */
      if (lj_char_isdigit(uchar(*p))) p++;  /* (2 digits at most) */
    }
    if (lj_char_isdigit(uchar(*p)))
      lj_err_caller(L, LJ_ERR_STRFMTW);
    *(form++) = '%';
    strncpy(form, strfrmt, (size_t)(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 unsigned LUA_INTFRM_T num2intfrm(lua_State *L, int arg)
  {
    if (sizeof(LUA_INTFRM_T) == 4) {
      return (LUA_INTFRM_T)lj_lib_checkbit(L, arg);
    } else {
      cTValue *o;
      lj_lib_checknumber(L, arg);
      o = L->base+arg-1;
      if (tvisint(o))
        return (LUA_INTFRM_T)intV(o);
      else
        return (LUA_INTFRM_T)numV(o);
    }
  }
  
  static unsigned LUA_INTFRM_T num2uintfrm(lua_State *L, int arg)
  {
    if (sizeof(LUA_INTFRM_T) == 4) {
      return (unsigned LUA_INTFRM_T)lj_lib_checkbit(L, arg);
    } else {
      cTValue *o;
      lj_lib_checknumber(L, arg);
      o = L->base+arg-1;
      if (tvisint(o))
        return (unsigned LUA_INTFRM_T)intV(o);
      else if ((int32_t)o->u32.hi < 0)
        return (unsigned LUA_INTFRM_T)(LUA_INTFRM_T)numV(o);
      else
        return (unsigned LUA_INTFRM_T)numV(o);
    }
  }
  
  static GCstr *meta_tostring(lua_State *L, int arg)
  {
    TValue *o = L->base+arg-1;
    cTValue *mo;
    lua_assert(o < L->top);  /* Caller already checks for existence. */
    if (LJ_LIKELY(tvisstr(o)))
      return strV(o);
    if (!tvisnil(mo = lj_meta_lookup(L, o, MM_tostring))) {
      copyTV(L, L->top++, mo);
      copyTV(L, L->top++, o);
      lua_call(L, 1, 1);
      L->top--;
      if (tvisstr(L->top))
        return strV(L->top);
      o = L->base+arg-1;
      copyTV(L, o, L->top);
    }
    if (tvisnumber(o)) {
      return lj_str_fromnumber(L, o);
    } else if (tvisnil(o)) {
      return lj_str_newlit(L, "nil");
    } else if (tvisfalse(o)) {
      return lj_str_newlit(L, "false");
    } else if (tvistrue(o)) {
      return lj_str_newlit(L, "true");
    } else {
      if (tvisfunc(o) && isffunc(funcV(o)))
        lj_str_pushf(L, "function: builtin#%d", funcV(o)->c.ffid);
      else
        lj_str_pushf(L, "%s: %p", lj_typename(o), lua_topointer(L, arg));
      L->top--;
      return strV(L->top);
    }
  }
  
  LJLIB_CF(string_format)
  {
    int arg = 1, top = (int)(L->top - L->base);
    GCstr *fmt = lj_lib_checkstr(L, arg);
    const char *strfrmt = strdata(fmt);
    const char *strfrmt_end = strfrmt + fmt->len;
    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_FMTSPEC];  /* to store the format (`%...') */
        char buff[MAX_FMTITEM];  /* to store the formatted item */
        if (++arg > top)
  	luaL_argerror(L, arg, lj_obj_typename[0]);
        strfrmt = scanformat(L, strfrmt, form);
        switch (*strfrmt++) {
        case 'c':
  	sprintf(buff, form, lj_lib_checkint(L, arg));
  	break;
        case 'd':  case 'i':
  	addintlen(form);
  	sprintf(buff, form, num2intfrm(L, arg));
  	break;
        case 'o':  case 'u':  case 'x':  case 'X':
  	addintlen(form);
  	sprintf(buff, form, num2uintfrm(L, arg));
  	break;
        case 'e':  case 'E': case 'f': case 'g': case 'G': case 'a': case 'A': {
  	TValue tv;
  	tv.n = lj_lib_checknum(L, arg);
  	if (LJ_UNLIKELY((tv.u32.hi << 1) >= 0xffe00000)) {
  	  /* Canonicalize output of non-finite values. */
  	  char *p, nbuf[LJ_STR_NUMBUF];
  	  size_t len = lj_str_bufnum(nbuf, &tv);
  	  if (strfrmt[-1] < 'a') {
  	    nbuf[len-3] = nbuf[len-3] - 0x20;
  	    nbuf[len-2] = nbuf[len-2] - 0x20;
  	    nbuf[len-1] = nbuf[len-1] - 0x20;
  	  }
  	  nbuf[len] = '\0';
  	  for (p = form; *p < 'A' && *p != '.'; p++) ;
  	  *p++ = 's'; *p = '\0';
  	  sprintf(buff, form, nbuf);
  	  break;
  	}
  	sprintf(buff, form, (double)tv.n);
  	break;
  	}
        case 'q':
  	addquoted(L, &b, arg);
  	continue;
        case 'p':
  	lj_str_pushf(L, "%p", lua_topointer(L, arg));
  	luaL_addvalue(&b);
  	continue;
        case 's': {
  	GCstr *str = meta_tostring(L, arg);
  	if (!strchr(form, '.') && str->len >= 100) {
  	  /* no precision and string is too long to be formatted;
  	     keep original string */
  	  setstrV(L, L->top++, str);
  	  luaL_addvalue(&b);
  	  continue;
  	}
  	sprintf(buff, form, strdata(str));
  	break;
  	}
        default:
  	lj_err_callerv(L, LJ_ERR_STRFMTO, *(strfrmt -1));
  	break;
        }
        luaL_addlstring(&b, buff, strlen(buff));
      }
    }
    luaL_pushresult(&b);
    return 1;
  }
  
  /* ------------------------------------------------------------------------ */
  
  #include "lj_libdef.h"
  
  LUALIB_API int luaopen_string(lua_State *L)
  {
    GCtab *mt;
    global_State *g;
    LJ_LIB_REG(L, LUA_STRLIBNAME, string);
  #if defined(LUA_COMPAT_GFIND) && !LJ_52
    lua_getfield(L, -1, "gmatch");
    lua_setfield(L, -2, "gfind");
  #endif
    mt = lj_tab_new(L, 0, 1);
    /* NOBARRIER: basemt is a GC root. */
    g = G(L);
    setgcref(basemt_it(g, LJ_TSTR), obj2gco(mt));
    settabV(L, lj_tab_setstr(L, mt, mmname_str(g, MM_index)), tabV(L->top-1));
    mt->nomm = (uint8_t)(~(1u<<MM_index));
    return 1;
  }
  
  