src/lib_string.c

   1 /*
   2 ** String library.
   3 ** Copyright (C) 2005-2023 Mike Pall. See Copyright Notice in luajit.h
   4 **
   5 ** Major portions taken verbatim or adapted from the Lua interpreter.
   6 ** Copyright (C) 1994-2008 Lua.org, PUC-Rio. See Copyright Notice in lua.h
   7 */
   8
   9 #define lib_string_c
  10 #define LUA_LIB
  11
  12 #include "lua.h"
  13 #include "lauxlib.h"
  14 #include "lualib.h"
  15
  16 #include "lj_obj.h"
  17 #include "lj_gc.h"
  18 #include "lj_err.h"
  19 #include "lj_buf.h"
  20 #include "lj_str.h"
  21 #include "lj_tab.h"
  22 #include "lj_meta.h"
  23 #include "lj_state.h"
  24 #include "lj_ff.h"
  25 #include "lj_bcdump.h"
  26 #include "lj_char.h"
  27 #include "lj_strfmt.h"
  28 #include "lj_lib.h"
  29
  30 /* ------------------------------------------------------------------------ */
  31
  32 #define LJLIB_MODULE_string
  33
  34 LJLIB_LUA(string_len) /*
  35   function(s)
  36     CHECK_str(s)
  37     return #s
  38   end
  39 */
  40
  41 LJLIB_ASM(string_byte)          LJLIB_REC(string_range 0)
  42 {
  43   GCstr *s = lj_lib_checkstr(L, 1);
  44   int32_t len = (int32_t)s->len;
  45   int32_t start = lj_lib_optint(L, 2, 1);
  46   int32_t stop = lj_lib_optint(L, 3, start);
  47   int32_t n, i;
  48   const unsigned char *p;
  49   if (stop < 0) stop += len+1;
  50   if (start < 0) start += len+1;
  51   if (start <= 0) start = 1;
  52   if (stop > len) stop = len;
  53   if (start > stop) return FFH_RES(0);  /* Empty interval: return no results. */
  54   start--;
  55   n = stop - start;
  56   if ((uint32_t)n > LUAI_MAXCSTACK)
  57     lj_err_caller(L, LJ_ERR_STRSLC);
  58   lj_state_checkstack(L, (MSize)n);
  59   p = (const unsigned char *)strdata(s) + start;
  60   for (i = 0; i < n; i++)
  61     setintV(L->base + i-1-LJ_FR2, p[i]);
  62   return FFH_RES(n);
  63 }
  64
  65 LJLIB_ASM(string_char)          LJLIB_REC(.)
  66 {
  67   int i, nargs = (int)(L->top - L->base);
  68   char *buf = lj_buf_tmp(L, (MSize)nargs);
  69   for (i = 1; i <= nargs; i++) {
  70     int32_t k = lj_lib_checkint(L, i);
  71     if (!checku8(k))
  72       lj_err_arg(L, i, LJ_ERR_BADVAL);
  73     buf[i-1] = (char)k;
  74   }
  75   setstrV(L, L->base-1-LJ_FR2, lj_str_new(L, buf, (size_t)nargs));
  76   return FFH_RES(1);
  77 }
  78
  79 LJLIB_ASM(string_sub)           LJLIB_REC(string_range 1)
  80 {
  81   lj_lib_checkstr(L, 1);
  82   lj_lib_checkint(L, 2);
  83   setintV(L->base+2, lj_lib_optint(L, 3, -1));
  84   return FFH_RETRY;
  85 }
  86
  87 LJLIB_CF(string_rep)            LJLIB_REC(.)
  88 {
  89   GCstr *s = lj_lib_checkstr(L, 1);
  90   int32_t rep = lj_lib_checkint(L, 2);
  91   GCstr *sep = lj_lib_optstr(L, 3);
  92   SBuf *sb = lj_buf_tmp_(L);
  93   if (sep && rep > 1) {
  94     GCstr *s2 = lj_buf_cat2str(L, sep, s);
  95     lj_buf_reset(sb);
  96     lj_buf_putstr(sb, s);
  97     s = s2;
  98     rep--;
  99   }
 100   sb = lj_buf_putstr_rep(sb, s, rep);
 101   setstrV(L, L->top-1, lj_buf_str(L, sb));
 102   lj_gc_check(L);
 103   return 1;
 104 }
 105
 106 LJLIB_ASM(string_reverse)  LJLIB_REC(string_op IRCALL_lj_buf_putstr_reverse)
 107 {
 108   lj_lib_checkstr(L, 1);
 109   return FFH_RETRY;
 110 }
 111 LJLIB_ASM_(string_lower)  LJLIB_REC(string_op IRCALL_lj_buf_putstr_lower)
 112 LJLIB_ASM_(string_upper)  LJLIB_REC(string_op IRCALL_lj_buf_putstr_upper)
 113
 114 /* ------------------------------------------------------------------------ */
 115
 116 static int writer_buf(lua_State *L, const void *p, size_t size, void *sb)
 117 {
 118   lj_buf_putmem((SBuf *)sb, p, (MSize)size);
 119   UNUSED(L);
 120   return 0;
 121 }
 122
 123 LJLIB_CF(string_dump)
 124 {
 125   GCproto *pt = lj_lib_checkLproto(L, 1, 1);
 126   uint32_t flags = 0;
 127   SBuf *sb;
 128   TValue *o = L->base+1;
 129   if (o < L->top) {
 130     if (tvisstr(o)) {
 131       const char *mode = strVdata(o);
 132       char c;
 133       while ((c = *mode++)) {
 134         if (c == 's') flags |= BCDUMP_F_STRIP;
 135         if (c == 'd') flags |= BCDUMP_F_DETERMINISTIC;
 136       }
 137     } else if (tvistruecond(o)) {
 138       flags |= BCDUMP_F_STRIP;
 139     }
 140   }
 141   sb = lj_buf_tmp_(L);  /* Assumes lj_bcwrite() doesn't use tmpbuf. */
 142   L->top = L->base+1;
 143   if (!pt || lj_bcwrite(L, pt, writer_buf, sb, flags))
 144     lj_err_caller(L, LJ_ERR_STRDUMP);
 145   setstrV(L, L->top-1, lj_buf_str(L, sb));
 146   lj_gc_check(L);
 147   return 1;
 148 }
 149
 150 /* ------------------------------------------------------------------------ */
 151
 152 /* macro to `unsign' a character */
 153 #define uchar(c)        ((unsigned char)(c))
 154
 155 #define CAP_UNFINISHED  (-1)
 156 #define CAP_POSITION    (-2)
 157
 158 typedef struct MatchState {
 159   const char *src_init;  /* init of source string */
 160   const char *src_end;  /* end (`\0') of source string */
 161   lua_State *L;
 162   int level;  /* total number of captures (finished or unfinished) */
 163   int depth;
 164   struct {
 165     const char *init;
 166     ptrdiff_t len;
 167   } capture[LUA_MAXCAPTURES];
 168 } MatchState;
 169
 170 #define L_ESC           '%'
 171
 172 static int check_capture(MatchState *ms, int l)
 173 {
 174   l -= '1';
 175   if (l < 0 || l >= ms->level || ms->capture[l].len == CAP_UNFINISHED)
 176     lj_err_caller(ms->L, LJ_ERR_STRCAPI);
 177   return l;
 178 }
 179
 180 static int capture_to_close(MatchState *ms)
 181 {
 182   int level = ms->level;
 183   for (level--; level>=0; level--)
 184     if (ms->capture[level].len == CAP_UNFINISHED) return level;
 185   lj_err_caller(ms->L, LJ_ERR_STRPATC);
 186   return 0;  /* unreachable */
 187 }
 188
 189 static const char *classend(MatchState *ms, const char *p)
 190 {
 191   switch (*p++) {
 192   case L_ESC:
 193     if (*p == '\0')
 194       lj_err_caller(ms->L, LJ_ERR_STRPATE);
 195     return p+1;
 196   case '[':
 197     if (*p == '^') p++;
 198     do {  /* look for a `]' */
 199       if (*p == '\0')
 200         lj_err_caller(ms->L, LJ_ERR_STRPATM);
 201       if (*(p++) == L_ESC && *p != '\0')
 202         p++;  /* skip escapes (e.g. `%]') */
 203     } while (*p != ']');
 204     return p+1;
 205   default:
 206     return p;
 207   }
 208 }
 209
 210 static const unsigned char match_class_map[32] = {
 211   0,LJ_CHAR_ALPHA,0,LJ_CHAR_CNTRL,LJ_CHAR_DIGIT,0,0,LJ_CHAR_GRAPH,0,0,0,0,
 212   LJ_CHAR_LOWER,0,0,0,LJ_CHAR_PUNCT,0,0,LJ_CHAR_SPACE,0,
 213   LJ_CHAR_UPPER,0,LJ_CHAR_ALNUM,LJ_CHAR_XDIGIT,0,0,0,0,0,0,0
 214 };
 215
 216 static int match_class(int c, int cl)
 217 {
 218   if ((cl & 0xc0) == 0x40) {
 219     int t = match_class_map[(cl&0x1f)];
 220     if (t) {
 221       t = lj_char_isa(c, t);
 222       return (cl & 0x20) ? t : !t;
 223     }
 224     if (cl == 'z') return c == 0;
 225     if (cl == 'Z') return c != 0;
 226   }
 227   return (cl == c);
 228 }
 229
 230 static int matchbracketclass(int c, const char *p, const char *ec)
 231 {
 232   int sig = 1;
 233   if (*(p+1) == '^') {
 234     sig = 0;
 235     p++;  /* skip the `^' */
 236   }
 237   while (++p < ec) {
 238     if (*p == L_ESC) {
 239       p++;
 240       if (match_class(c, uchar(*p)))
 241         return sig;
 242     }
 243     else if ((*(p+1) == '-') && (p+2 < ec)) {
 244       p+=2;
 245       if (uchar(*(p-2)) <= c && c <= uchar(*p))
 246         return sig;
 247     }
 248     else if (uchar(*p) == c) return sig;
 249   }
 250   return !sig;
 251 }
 252
 253 static int singlematch(int c, const char *p, const char *ep)
 254 {
 255   switch (*p) {
 256   case '.': return 1;  /* matches any char */
 257   case L_ESC: return match_class(c, uchar(*(p+1)));
 258   case '[': return matchbracketclass(c, p, ep-1);
 259   default:  return (uchar(*p) == c);
 260   }
 261 }
 262
 263 static const char *match(MatchState *ms, const char *s, const char *p);
 264
 265 static const char *matchbalance(MatchState *ms, const char *s, const char *p)
 266 {
 267   if (*p == 0 || *(p+1) == 0)
 268     lj_err_caller(ms->L, LJ_ERR_STRPATU);
 269   if (*s != *p) {
 270     return NULL;
 271   } else {
 272     int b = *p;
 273     int e = *(p+1);
 274     int cont = 1;
 275     while (++s < ms->src_end) {
 276       if (*s == e) {
 277         if (--cont == 0) return s+1;
 278       } else if (*s == b) {
 279         cont++;
 280       }
 281     }
 282   }
 283   return NULL;  /* string ends out of balance */
 284 }
 285
 286 static const char *max_expand(MatchState *ms, const char *s,
 287                               const char *p, const char *ep)
 288 {
 289   ptrdiff_t i = 0;  /* counts maximum expand for item */
 290   while ((s+i)<ms->src_end && singlematch(uchar(*(s+i)), p, ep))
 291     i++;
 292   /* keeps trying to match with the maximum repetitions */
 293   while (i>=0) {
 294     const char *res = match(ms, (s+i), ep+1);
 295     if (res) return res;
 296     i--;  /* else didn't match; reduce 1 repetition to try again */
 297   }
 298   return NULL;
 299 }
 300
 301 static const char *min_expand(MatchState *ms, const char *s,
 302                               const char *p, const char *ep)
 303 {
 304   for (;;) {
 305     const char *res = match(ms, s, ep+1);
 306     if (res != NULL)
 307       return res;
 308     else if (s<ms->src_end && singlematch(uchar(*s), p, ep))
 309       s++;  /* try with one more repetition */
 310     else
 311       return NULL;
 312   }
 313 }
 314
 315 static const char *start_capture(MatchState *ms, const char *s,
 316                                  const char *p, int what)
 317 {
 318   const char *res;
 319   int level = ms->level;
 320   if (level >= LUA_MAXCAPTURES) lj_err_caller(ms->L, LJ_ERR_STRCAPN);
 321   ms->capture[level].init = s;
 322   ms->capture[level].len = what;
 323   ms->level = level+1;
 324   if ((res=match(ms, s, p)) == NULL)  /* match failed? */
 325     ms->level--;  /* undo capture */
 326   return res;
 327 }
 328
 329 static const char *end_capture(MatchState *ms, const char *s,
 330                                const char *p)
 331 {
 332   int l = capture_to_close(ms);
 333   const char *res;
 334   ms->capture[l].len = s - ms->capture[l].init;  /* close capture */
 335   if ((res = match(ms, s, p)) == NULL)  /* match failed? */
 336     ms->capture[l].len = CAP_UNFINISHED;  /* undo capture */
 337   return res;
 338 }
 339
 340 static const char *match_capture(MatchState *ms, const char *s, int l)
 341 {
 342   size_t len;
 343   l = check_capture(ms, l);
 344   len = (size_t)ms->capture[l].len;
 345   if ((size_t)(ms->src_end-s) >= len &&
 346       memcmp(ms->capture[l].init, s, len) == 0)
 347     return s+len;
 348   else
 349     return NULL;
 350 }
 351
 352 static const char *match(MatchState *ms, const char *s, const char *p)
 353 {
 354   if (++ms->depth > LJ_MAX_XLEVEL)
 355     lj_err_caller(ms->L, LJ_ERR_STRPATX);
 356   init: /* using goto's to optimize tail recursion */
 357   switch (*p) {
 358   case '(':  /* start capture */
 359     if (*(p+1) == ')')  /* position capture? */
 360       s = start_capture(ms, s, p+2, CAP_POSITION);
 361     else
 362       s = start_capture(ms, s, p+1, CAP_UNFINISHED);
 363     break;
 364   case ')':  /* end capture */
 365     s = end_capture(ms, s, p+1);
 366     break;
 367   case L_ESC:
 368     switch (*(p+1)) {
 369     case 'b':  /* balanced string? */
 370       s = matchbalance(ms, s, p+2);
 371       if (s == NULL) break;
 372       p+=4;
 373       goto init;  /* else s = match(ms, s, p+4); */
 374     case 'f': {  /* frontier? */
 375       const char *ep; char previous;
 376       p += 2;
 377       if (*p != '[')
 378         lj_err_caller(ms->L, LJ_ERR_STRPATB);
 379       ep = classend(ms, p);  /* points to what is next */
 380       previous = (s == ms->src_init) ? '\0' : *(s-1);
 381       if (matchbracketclass(uchar(previous), p, ep-1) ||
 382          !matchbracketclass(uchar(*s), p, ep-1)) { s = NULL; break; }
 383       p=ep;
 384       goto init;  /* else s = match(ms, s, ep); */
 385       }
 386     default:
 387       if (lj_char_isdigit(uchar(*(p+1)))) {  /* capture results (%0-%9)? */
 388         s = match_capture(ms, s, uchar(*(p+1)));
 389         if (s == NULL) break;
 390         p+=2;
 391         goto init;  /* else s = match(ms, s, p+2) */
 392       }
 393       goto dflt;  /* case default */
 394     }
 395     break;
 396   case '\0':  /* end of pattern */
 397     break;  /* match succeeded */
 398   case '$':
 399     /* is the `$' the last char in pattern? */
 400     if (*(p+1) != '\0') goto dflt;
 401     if (s != ms->src_end) s = NULL;  /* check end of string */
 402     break;
 403   default: dflt: {  /* it is a pattern item */
 404     const char *ep = classend(ms, p);  /* points to what is next */
 405     int m = s<ms->src_end && singlematch(uchar(*s), p, ep);
 406     switch (*ep) {
 407     case '?': {  /* optional */
 408       const char *res;
 409       if (m && ((res=match(ms, s+1, ep+1)) != NULL)) {
 410         s = res;
 411         break;
 412       }
 413       p=ep+1;
 414       goto init;  /* else s = match(ms, s, ep+1); */
 415       }
 416     case '*':  /* 0 or more repetitions */
 417       s = max_expand(ms, s, p, ep);
 418       break;
 419     case '+':  /* 1 or more repetitions */
 420       s = (m ? max_expand(ms, s+1, p, ep) : NULL);
 421       break;
 422     case '-':  /* 0 or more repetitions (minimum) */
 423       s = min_expand(ms, s, p, ep);
 424       break;
 425     default:
 426       if (m) { s++; p=ep; goto init; }  /* else s = match(ms, s+1, ep); */
 427       s = NULL;
 428       break;
 429     }
 430     break;
 431     }
 432   }
 433   ms->depth--;
 434   return s;
 435 }
 436
 437 static void push_onecapture(MatchState *ms, int i, const char *s, const char *e)
 438 {
 439   if (i >= ms->level) {
 440     if (i == 0)  /* ms->level == 0, too */
 441       lua_pushlstring(ms->L, s, (size_t)(e - s));  /* add whole match */
 442     else
 443       lj_err_caller(ms->L, LJ_ERR_STRCAPI);
 444   } else {
 445     ptrdiff_t l = ms->capture[i].len;
 446     if (l == CAP_UNFINISHED) lj_err_caller(ms->L, LJ_ERR_STRCAPU);
 447     if (l == CAP_POSITION)
 448       lua_pushinteger(ms->L, ms->capture[i].init - ms->src_init + 1);
 449     else
 450       lua_pushlstring(ms->L, ms->capture[i].init, (size_t)l);
 451   }
 452 }
 453
 454 static int push_captures(MatchState *ms, const char *s, const char *e)
 455 {
 456   int i;
 457   int nlevels = (ms->level == 0 && s) ? 1 : ms->level;
 458   luaL_checkstack(ms->L, nlevels, "too many captures");
 459   for (i = 0; i < nlevels; i++)
 460     push_onecapture(ms, i, s, e);
 461   return nlevels;  /* number of strings pushed */
 462 }
 463
 464 static int str_find_aux(lua_State *L, int find)
 465 {
 466   GCstr *s = lj_lib_checkstr(L, 1);
 467   GCstr *p = lj_lib_checkstr(L, 2);
 468   int32_t start = lj_lib_optint(L, 3, 1);
 469   MSize st;
 470   if (start < 0) start += (int32_t)s->len; else start--;
 471   if (start < 0) start = 0;
 472   st = (MSize)start;
 473   if (st > s->len) {
 474 #if LJ_52
 475     setnilV(L->top-1);
 476     return 1;
 477 #else
 478     st = s->len;
 479 #endif
 480   }
 481   if (find && ((L->base+3 < L->top && tvistruecond(L->base+3)) ||
 482                !lj_str_haspattern(p))) {  /* Search for fixed string. */
 483     const char *q = lj_str_find(strdata(s)+st, strdata(p), s->len-st, p->len);
 484     if (q) {
 485       setintV(L->top-2, (int32_t)(q-strdata(s)) + 1);
 486       setintV(L->top-1, (int32_t)(q-strdata(s)) + (int32_t)p->len);
 487       return 2;
 488     }
 489   } else {  /* Search for pattern. */
 490     MatchState ms;
 491     const char *pstr = strdata(p);
 492     const char *sstr = strdata(s) + st;
 493     int anchor = 0;
 494     if (*pstr == '^') { pstr++; anchor = 1; }
 495     ms.L = L;
 496     ms.src_init = strdata(s);
 497     ms.src_end = strdata(s) + s->len;
 498     do {  /* Loop through string and try to match the pattern. */
 499       const char *q;
 500       ms.level = ms.depth = 0;
 501       q = match(&ms, sstr, pstr);
 502       if (q) {
 503         if (find) {
 504           setintV(L->top++, (int32_t)(sstr-(strdata(s)-1)));
 505           setintV(L->top++, (int32_t)(q-strdata(s)));
 506           return push_captures(&ms, NULL, NULL) + 2;
 507         } else {
 508           return push_captures(&ms, sstr, q);
 509         }
 510       }
 511     } while (sstr++ < ms.src_end && !anchor);
 512   }
 513   setnilV(L->top-1);  /* Not found. */
 514   return 1;
 515 }
 516
 517 LJLIB_CF(string_find)           LJLIB_REC(.)
 518 {
 519   return str_find_aux(L, 1);
 520 }
 521
 522 LJLIB_CF(string_match)
 523 {
 524   return str_find_aux(L, 0);
 525 }
 526
 527 LJLIB_NOREG LJLIB_CF(string_gmatch_aux)
 528 {
 529   const char *p = strVdata(lj_lib_upvalue(L, 2));
 530   GCstr *str = strV(lj_lib_upvalue(L, 1));
 531   const char *s = strdata(str);
 532   TValue *tvpos = lj_lib_upvalue(L, 3);
 533   const char *src = s + tvpos->u32.lo;
 534   MatchState ms;
 535   ms.L = L;
 536   ms.src_init = s;
 537   ms.src_end = s + str->len;
 538   for (; src <= ms.src_end; src++) {
 539     const char *e;
 540     ms.level = ms.depth = 0;
 541     if ((e = match(&ms, src, p)) != NULL) {
 542       int32_t pos = (int32_t)(e - s);
 543       if (e == src) pos++;  /* Ensure progress for empty match. */
 544       tvpos->u32.lo = (uint32_t)pos;
 545       return push_captures(&ms, src, e);
 546     }
 547   }
 548   return 0;  /* not found */
 549 }
 550
 551 LJLIB_CF(string_gmatch)
 552 {
 553   lj_lib_checkstr(L, 1);
 554   lj_lib_checkstr(L, 2);
 555   L->top = L->base+3;
 556   (L->top-1)->u64 = 0;
 557   lj_lib_pushcc(L, lj_cf_string_gmatch_aux, FF_string_gmatch_aux, 3);
 558   return 1;
 559 }
 560
 561 static void add_s(MatchState *ms, luaL_Buffer *b, const char *s, const char *e)
 562 {
 563   size_t l, i;
 564   const char *news = lua_tolstring(ms->L, 3, &l);
 565   for (i = 0; i < l; i++) {
 566     if (news[i] != L_ESC) {
 567       luaL_addchar(b, news[i]);
 568     } else {
 569       i++;  /* skip ESC */
 570       if (!lj_char_isdigit(uchar(news[i]))) {
 571         luaL_addchar(b, news[i]);
 572       } else if (news[i] == '0') {
 573         luaL_addlstring(b, s, (size_t)(e - s));
 574       } else {
 575         push_onecapture(ms, news[i] - '1', s, e);
 576         luaL_addvalue(b);  /* add capture to accumulated result */
 577       }
 578     }
 579   }
 580 }
 581
 582 static void add_value(MatchState *ms, luaL_Buffer *b,
 583                       const char *s, const char *e)
 584 {
 585   lua_State *L = ms->L;
 586   switch (lua_type(L, 3)) {
 587     case LUA_TNUMBER:
 588     case LUA_TSTRING: {
 589       add_s(ms, b, s, e);
 590       return;
 591     }
 592     case LUA_TFUNCTION: {
 593       int n;
 594       lua_pushvalue(L, 3);
 595       n = push_captures(ms, s, e);
 596       lua_call(L, n, 1);
 597       break;
 598     }
 599     case LUA_TTABLE: {
 600       push_onecapture(ms, 0, s, e);
 601       lua_gettable(L, 3);
 602       break;
 603     }
 604   }
 605   if (!lua_toboolean(L, -1)) {  /* nil or false? */
 606     lua_pop(L, 1);
 607     lua_pushlstring(L, s, (size_t)(e - s));  /* keep original text */
 608   } else if (!lua_isstring(L, -1)) {
 609     lj_err_callerv(L, LJ_ERR_STRGSRV, luaL_typename(L, -1));
 610   }
 611   luaL_addvalue(b);  /* add result to accumulator */
 612 }
 613
 614 LJLIB_CF(string_gsub)
 615 {
 616   size_t srcl;
 617   const char *src = luaL_checklstring(L, 1, &srcl);
 618   const char *p = luaL_checkstring(L, 2);
 619   int  tr = lua_type(L, 3);
 620   int max_s = luaL_optint(L, 4, (int)(srcl+1));
 621   int anchor = (*p == '^') ? (p++, 1) : 0;
 622   int n = 0;
 623   MatchState ms;
 624   luaL_Buffer b;
 625   if (!(tr == LUA_TNUMBER || tr == LUA_TSTRING ||
 626         tr == LUA_TFUNCTION || tr == LUA_TTABLE))
 627     lj_err_arg(L, 3, LJ_ERR_NOSFT);
 628   luaL_buffinit(L, &b);
 629   ms.L = L;
 630   ms.src_init = src;
 631   ms.src_end = src+srcl;
 632   while (n < max_s) {
 633     const char *e;
 634     ms.level = ms.depth = 0;
 635     e = match(&ms, src, p);
 636     if (e) {
 637       n++;
 638       add_value(&ms, &b, src, e);
 639     }
 640     if (e && e>src) /* non empty match? */
 641       src = e;  /* skip it */
 642     else if (src < ms.src_end)
 643       luaL_addchar(&b, *src++);
 644     else
 645       break;
 646     if (anchor)
 647       break;
 648   }
 649   luaL_addlstring(&b, src, (size_t)(ms.src_end-src));
 650   luaL_pushresult(&b);
 651   lua_pushinteger(L, n);  /* number of substitutions */
 652   return 2;
 653 }
 654
 655 /* ------------------------------------------------------------------------ */
 656
 657 LJLIB_CF(string_format)         LJLIB_REC(.)
 658 {
 659   int retry = 0;
 660   SBuf *sb;
 661   do {
 662     sb = lj_buf_tmp_(L);
 663     retry = lj_strfmt_putarg(L, sb, 1, -retry);
 664   } while (retry > 0);
 665   setstrV(L, L->top-1, lj_buf_str(L, sb));
 666   lj_gc_check(L);
 667   return 1;
 668 }
 669
 670 /* ------------------------------------------------------------------------ */
 671
 672 #include "lj_libdef.h"
 673
 674 LUALIB_API int luaopen_string(lua_State *L)
 675 {
 676   GCtab *mt;
 677   global_State *g;
 678   LJ_LIB_REG(L, LUA_STRLIBNAME, string);
 679   mt = lj_tab_new(L, 0, 1);
 680   /* NOBARRIER: basemt is a GC root. */
 681   g = G(L);
 682   setgcref(basemt_it(g, LJ_TSTR), obj2gco(mt));
 683   settabV(L, lj_tab_setstr(L, mt, mmname_str(g, MM_index)), tabV(L->top-1));
 684   mt->nomm = (uint8_t)(~(1u<<MM_index));
 685 #if LJ_HASBUFFER
 686   lj_lib_prereg(L, LUA_STRLIBNAME ".buffer", luaopen_string_buffer, tabV(L->top-1));
 687 #endif
 688   return 1;
 689 }
 690