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lstrlib.c (57546B)


      1 /*
      2 ** $Id: lstrlib.c $
      3 ** Standard library for string operations and pattern-matching
      4 ** See Copyright Notice in lua.h
      5 */
      6 
      7 #define lstrlib_c
      8 #define LUA_LIB
      9 
     10 #include "lprefix.h"
     11 
     12 
     13 #include <ctype.h>
     14 #include <float.h>
     15 #include <limits.h>
     16 #include <locale.h>
     17 #include <math.h>
     18 #include <stddef.h>
     19 #include <stdio.h>
     20 #include <stdlib.h>
     21 #include <string.h>
     22 
     23 #include "lua.h"
     24 
     25 #include "lauxlib.h"
     26 #include "lualib.h"
     27 #include "llimits.h"
     28 
     29 
     30 /*
     31 ** maximum number of captures that a pattern can do during
     32 ** pattern-matching. This limit is arbitrary, but must fit in
     33 ** an unsigned char.
     34 */
     35 #if !defined(LUA_MAXCAPTURES)
     36 #define LUA_MAXCAPTURES		32
     37 #endif
     38 
     39 
     40 static int str_len (lua_State *L) {
     41   size_t l;
     42   luaL_checklstring(L, 1, &l);
     43   lua_pushinteger(L, (lua_Integer)l);
     44   return 1;
     45 }
     46 
     47 
     48 /*
     49 ** translate a relative initial string position
     50 ** (negative means back from end): clip result to [1, inf).
     51 ** The length of any string in Lua must fit in a lua_Integer,
     52 ** so there are no overflows in the casts.
     53 ** The inverted comparison avoids a possible overflow
     54 ** computing '-pos'.
     55 */
     56 static size_t posrelatI (lua_Integer pos, size_t len) {
     57   if (pos > 0)
     58     return (size_t)pos;
     59   else if (pos == 0)
     60     return 1;
     61   else if (pos < -(lua_Integer)len)  /* inverted comparison */
     62     return 1;  /* clip to 1 */
     63   else return len + (size_t)pos + 1;
     64 }
     65 
     66 
     67 /*
     68 ** Gets an optional ending string position from argument 'arg',
     69 ** with default value 'def'.
     70 ** Negative means back from end: clip result to [0, len]
     71 */
     72 static size_t getendpos (lua_State *L, int arg, lua_Integer def,
     73                          size_t len) {
     74   lua_Integer pos = luaL_optinteger(L, arg, def);
     75   if (pos > (lua_Integer)len)
     76     return len;
     77   else if (pos >= 0)
     78     return (size_t)pos;
     79   else if (pos < -(lua_Integer)len)
     80     return 0;
     81   else return len + (size_t)pos + 1;
     82 }
     83 
     84 
     85 static int str_sub (lua_State *L) {
     86   size_t l;
     87   const char *s = luaL_checklstring(L, 1, &l);
     88   size_t start = posrelatI(luaL_checkinteger(L, 2), l);
     89   size_t end = getendpos(L, 3, -1, l);
     90   if (start <= end)
     91     lua_pushlstring(L, s + start - 1, (end - start) + 1);
     92   else lua_pushliteral(L, "");
     93   return 1;
     94 }
     95 
     96 
     97 static int str_reverse (lua_State *L) {
     98   size_t l, i;
     99   luaL_Buffer b;
    100   const char *s = luaL_checklstring(L, 1, &l);
    101   char *p = luaL_buffinitsize(L, &b, l);
    102   for (i = 0; i < l; i++)
    103     p[i] = s[l - i - 1];
    104   luaL_pushresultsize(&b, l);
    105   return 1;
    106 }
    107 
    108 
    109 static int str_lower (lua_State *L) {
    110   size_t l;
    111   size_t i;
    112   luaL_Buffer b;
    113   const char *s = luaL_checklstring(L, 1, &l);
    114   char *p = luaL_buffinitsize(L, &b, l);
    115   for (i=0; i<l; i++)
    116     p[i] = cast_char(tolower(cast_uchar(s[i])));
    117   luaL_pushresultsize(&b, l);
    118   return 1;
    119 }
    120 
    121 
    122 static int str_upper (lua_State *L) {
    123   size_t l;
    124   size_t i;
    125   luaL_Buffer b;
    126   const char *s = luaL_checklstring(L, 1, &l);
    127   char *p = luaL_buffinitsize(L, &b, l);
    128   for (i=0; i<l; i++)
    129     p[i] = cast_char(toupper(cast_uchar(s[i])));
    130   luaL_pushresultsize(&b, l);
    131   return 1;
    132 }
    133 
    134 
    135 static int str_rep (lua_State *L) {
    136   size_t l, lsep;
    137   const char *s = luaL_checklstring(L, 1, &l);
    138   lua_Integer n = luaL_checkinteger(L, 2);
    139   const char *sep = luaL_optlstring(L, 3, "", &lsep);
    140   if (n <= 0)
    141     lua_pushliteral(L, "");
    142   else if (l_unlikely(l + lsep < l || l + lsep > MAX_SIZE / cast_sizet(n)))
    143     return luaL_error(L, "resulting string too large");
    144   else {
    145     size_t totallen = ((size_t)n * (l + lsep)) - lsep;
    146     luaL_Buffer b;
    147     char *p = luaL_buffinitsize(L, &b, totallen);
    148     while (n-- > 1) {  /* first n-1 copies (followed by separator) */
    149       memcpy(p, s, l * sizeof(char)); p += l;
    150       if (lsep > 0) {  /* empty 'memcpy' is not that cheap */
    151         memcpy(p, sep, lsep * sizeof(char));
    152         p += lsep;
    153       }
    154     }
    155     memcpy(p, s, l * sizeof(char));  /* last copy (not followed by separator) */
    156     luaL_pushresultsize(&b, totallen);
    157   }
    158   return 1;
    159 }
    160 
    161 
    162 static int str_byte (lua_State *L) {
    163   size_t l;
    164   const char *s = luaL_checklstring(L, 1, &l);
    165   lua_Integer pi = luaL_optinteger(L, 2, 1);
    166   size_t posi = posrelatI(pi, l);
    167   size_t pose = getendpos(L, 3, pi, l);
    168   int n, i;
    169   if (posi > pose) return 0;  /* empty interval; return no values */
    170   if (l_unlikely(pose - posi >= (size_t)INT_MAX))  /* arithmetic overflow? */
    171     return luaL_error(L, "string slice too long");
    172   n = (int)(pose -  posi) + 1;
    173   luaL_checkstack(L, n, "string slice too long");
    174   for (i=0; i<n; i++)
    175     lua_pushinteger(L, cast_uchar(s[posi + cast_uint(i) - 1]));
    176   return n;
    177 }
    178 
    179 
    180 static int str_char (lua_State *L) {
    181   int n = lua_gettop(L);  /* number of arguments */
    182   int i;
    183   luaL_Buffer b;
    184   char *p = luaL_buffinitsize(L, &b, cast_uint(n));
    185   for (i=1; i<=n; i++) {
    186     lua_Unsigned c = (lua_Unsigned)luaL_checkinteger(L, i);
    187     luaL_argcheck(L, c <= (lua_Unsigned)UCHAR_MAX, i, "value out of range");
    188     p[i - 1] = cast_char(cast_uchar(c));
    189   }
    190   luaL_pushresultsize(&b, cast_uint(n));
    191   return 1;
    192 }
    193 
    194 
    195 /*
    196 ** Buffer to store the result of 'string.dump'. It must be initialized
    197 ** after the call to 'lua_dump', to ensure that the function is on the
    198 ** top of the stack when 'lua_dump' is called. ('luaL_buffinit' might
    199 ** push stuff.)
    200 */
    201 struct str_Writer {
    202   int init;  /* true iff buffer has been initialized */
    203   luaL_Buffer B;
    204 };
    205 
    206 
    207 static int writer (lua_State *L, const void *b, size_t size, void *ud) {
    208   struct str_Writer *state = (struct str_Writer *)ud;
    209   if (!state->init) {
    210     state->init = 1;
    211     luaL_buffinit(L, &state->B);
    212   }
    213   if (b == NULL) {  /* finishing dump? */
    214     luaL_pushresult(&state->B);  /* push result */
    215     lua_replace(L, 1);  /* move it to reserved slot */
    216   }
    217   else
    218     luaL_addlstring(&state->B, (const char *)b, size);
    219   return 0;
    220 }
    221 
    222 
    223 static int str_dump (lua_State *L) {
    224   struct str_Writer state;
    225   int strip = lua_toboolean(L, 2);
    226   luaL_argcheck(L, lua_type(L, 1) == LUA_TFUNCTION && !lua_iscfunction(L, 1),
    227                    1, "Lua function expected");
    228   /* ensure function is on the top of the stack and vacate slot 1 */
    229   lua_pushvalue(L, 1);
    230   state.init = 0;
    231   lua_dump(L, writer, &state, strip);
    232   lua_settop(L, 1);  /* leave final result on top */
    233   return 1;
    234 }
    235 
    236 
    237 
    238 /*
    239 ** {======================================================
    240 ** METAMETHODS
    241 ** =======================================================
    242 */
    243 
    244 #if defined(LUA_NOCVTS2N)	/* { */
    245 
    246 /* no coercion from strings to numbers */
    247 
    248 static const luaL_Reg stringmetamethods[] = {
    249   {"__index", NULL},  /* placeholder */
    250   {NULL, NULL}
    251 };
    252 
    253 #else		/* }{ */
    254 
    255 static int tonum (lua_State *L, int arg) {
    256   if (lua_type(L, arg) == LUA_TNUMBER) {  /* already a number? */
    257     lua_pushvalue(L, arg);
    258     return 1;
    259   }
    260   else {  /* check whether it is a numerical string */
    261     size_t len;
    262     const char *s = lua_tolstring(L, arg, &len);
    263     return (s != NULL && lua_stringtonumber(L, s) == len + 1);
    264   }
    265 }
    266 
    267 
    268 static void trymt (lua_State *L, const char *mtname) {
    269   lua_settop(L, 2);  /* back to the original arguments */
    270   if (l_unlikely(lua_type(L, 2) == LUA_TSTRING ||
    271                  !luaL_getmetafield(L, 2, mtname)))
    272     luaL_error(L, "attempt to %s a '%s' with a '%s'", mtname + 2,
    273                   luaL_typename(L, -2), luaL_typename(L, -1));
    274   lua_insert(L, -3);  /* put metamethod before arguments */
    275   lua_call(L, 2, 1);  /* call metamethod */
    276 }
    277 
    278 
    279 static int arith (lua_State *L, int op, const char *mtname) {
    280   if (tonum(L, 1) && tonum(L, 2))
    281     lua_arith(L, op);  /* result will be on the top */
    282   else
    283     trymt(L, mtname);
    284   return 1;
    285 }
    286 
    287 
    288 static int arith_add (lua_State *L) {
    289   return arith(L, LUA_OPADD, "__add");
    290 }
    291 
    292 static int arith_sub (lua_State *L) {
    293   return arith(L, LUA_OPSUB, "__sub");
    294 }
    295 
    296 static int arith_mul (lua_State *L) {
    297   return arith(L, LUA_OPMUL, "__mul");
    298 }
    299 
    300 static int arith_mod (lua_State *L) {
    301   return arith(L, LUA_OPMOD, "__mod");
    302 }
    303 
    304 static int arith_pow (lua_State *L) {
    305   return arith(L, LUA_OPPOW, "__pow");
    306 }
    307 
    308 static int arith_div (lua_State *L) {
    309   return arith(L, LUA_OPDIV, "__div");
    310 }
    311 
    312 static int arith_idiv (lua_State *L) {
    313   return arith(L, LUA_OPIDIV, "__idiv");
    314 }
    315 
    316 static int arith_unm (lua_State *L) {
    317   return arith(L, LUA_OPUNM, "__unm");
    318 }
    319 
    320 
    321 static const luaL_Reg stringmetamethods[] = {
    322   {"__add", arith_add},
    323   {"__sub", arith_sub},
    324   {"__mul", arith_mul},
    325   {"__mod", arith_mod},
    326   {"__pow", arith_pow},
    327   {"__div", arith_div},
    328   {"__idiv", arith_idiv},
    329   {"__unm", arith_unm},
    330   {"__index", NULL},  /* placeholder */
    331   {NULL, NULL}
    332 };
    333 
    334 #endif		/* } */
    335 
    336 /* }====================================================== */
    337 
    338 /*
    339 ** {======================================================
    340 ** PATTERN MATCHING
    341 ** =======================================================
    342 */
    343 
    344 
    345 #define CAP_UNFINISHED	(-1)
    346 #define CAP_POSITION	(-2)
    347 
    348 
    349 typedef struct MatchState {
    350   const char *src_init;  /* init of source string */
    351   const char *src_end;  /* end ('\0') of source string */
    352   const char *p_end;  /* end ('\0') of pattern */
    353   lua_State *L;
    354   int matchdepth;  /* control for recursive depth (to avoid C stack overflow) */
    355   int level;  /* total number of captures (finished or unfinished) */
    356   struct {
    357     const char *init;
    358     ptrdiff_t len;  /* length or special value (CAP_*) */
    359   } capture[LUA_MAXCAPTURES];
    360 } MatchState;
    361 
    362 
    363 /* recursive function */
    364 static const char *match (MatchState *ms, const char *s, const char *p);
    365 
    366 
    367 /* maximum recursion depth for 'match' */
    368 #if !defined(MAXCCALLS)
    369 #define MAXCCALLS	200
    370 #endif
    371 
    372 
    373 #define L_ESC		'%'
    374 #define SPECIALS	"^$*+?.([%-"
    375 
    376 
    377 static int check_capture (MatchState *ms, int l) {
    378   l -= '1';
    379   if (l_unlikely(l < 0 || l >= ms->level ||
    380                  ms->capture[l].len == CAP_UNFINISHED))
    381     return luaL_error(ms->L, "invalid capture index %%%d", l + 1);
    382   return l;
    383 }
    384 
    385 
    386 static int capture_to_close (MatchState *ms) {
    387   int level = ms->level;
    388   for (level--; level>=0; level--)
    389     if (ms->capture[level].len == CAP_UNFINISHED) return level;
    390   return luaL_error(ms->L, "invalid pattern capture");
    391 }
    392 
    393 
    394 static const char *classend (MatchState *ms, const char *p) {
    395   switch (*p++) {
    396     case L_ESC: {
    397       if (l_unlikely(p == ms->p_end))
    398         luaL_error(ms->L, "malformed pattern (ends with '%%')");
    399       return p+1;
    400     }
    401     case '[': {
    402       if (*p == '^') p++;
    403       do {  /* look for a ']' */
    404         if (l_unlikely(p == ms->p_end))
    405           luaL_error(ms->L, "malformed pattern (missing ']')");
    406         if (*(p++) == L_ESC && p < ms->p_end)
    407           p++;  /* skip escapes (e.g. '%]') */
    408       } while (*p != ']');
    409       return p+1;
    410     }
    411     default: {
    412       return p;
    413     }
    414   }
    415 }
    416 
    417 
    418 static int match_class (int c, int cl) {
    419   int res;
    420   switch (tolower(cl)) {
    421     case 'a' : res = isalpha(c); break;
    422     case 'c' : res = iscntrl(c); break;
    423     case 'd' : res = isdigit(c); break;
    424     case 'g' : res = isgraph(c); break;
    425     case 'l' : res = islower(c); break;
    426     case 'p' : res = ispunct(c); break;
    427     case 's' : res = isspace(c); break;
    428     case 'u' : res = isupper(c); break;
    429     case 'w' : res = isalnum(c); break;
    430     case 'x' : res = isxdigit(c); break;
    431     case 'z' : res = (c == 0); break;  /* deprecated option */
    432     default: return (cl == c);
    433   }
    434   return (islower(cl) ? res : !res);
    435 }
    436 
    437 
    438 static int matchbracketclass (int c, const char *p, const char *ec) {
    439   int sig = 1;
    440   if (*(p+1) == '^') {
    441     sig = 0;
    442     p++;  /* skip the '^' */
    443   }
    444   while (++p < ec) {
    445     if (*p == L_ESC) {
    446       p++;
    447       if (match_class(c, cast_uchar(*p)))
    448         return sig;
    449     }
    450     else if ((*(p+1) == '-') && (p+2 < ec)) {
    451       p+=2;
    452       if (cast_uchar(*(p-2)) <= c && c <= cast_uchar(*p))
    453         return sig;
    454     }
    455     else if (cast_uchar(*p) == c) return sig;
    456   }
    457   return !sig;
    458 }
    459 
    460 
    461 static int singlematch (MatchState *ms, const char *s, const char *p,
    462                         const char *ep) {
    463   if (s >= ms->src_end)
    464     return 0;
    465   else {
    466     int c = cast_uchar(*s);
    467     switch (*p) {
    468       case '.': return 1;  /* matches any char */
    469       case L_ESC: return match_class(c, cast_uchar(*(p+1)));
    470       case '[': return matchbracketclass(c, p, ep-1);
    471       default:  return (cast_uchar(*p) == c);
    472     }
    473   }
    474 }
    475 
    476 
    477 static const char *matchbalance (MatchState *ms, const char *s,
    478                                    const char *p) {
    479   if (l_unlikely(p >= ms->p_end - 1))
    480     luaL_error(ms->L, "malformed pattern (missing arguments to '%%b')");
    481   if (*s != *p) return NULL;
    482   else {
    483     int b = *p;
    484     int e = *(p+1);
    485     int cont = 1;
    486     while (++s < ms->src_end) {
    487       if (*s == e) {
    488         if (--cont == 0) return s+1;
    489       }
    490       else if (*s == b) cont++;
    491     }
    492   }
    493   return NULL;  /* string ends out of balance */
    494 }
    495 
    496 
    497 static const char *max_expand (MatchState *ms, const char *s,
    498                                  const char *p, const char *ep) {
    499   ptrdiff_t i = 0;  /* counts maximum expand for item */
    500   while (singlematch(ms, s + i, p, ep))
    501     i++;
    502   /* keeps trying to match with the maximum repetitions */
    503   while (i>=0) {
    504     const char *res = match(ms, (s+i), ep+1);
    505     if (res) return res;
    506     i--;  /* else didn't match; reduce 1 repetition to try again */
    507   }
    508   return NULL;
    509 }
    510 
    511 
    512 static const char *min_expand (MatchState *ms, const char *s,
    513                                  const char *p, const char *ep) {
    514   for (;;) {
    515     const char *res = match(ms, s, ep+1);
    516     if (res != NULL)
    517       return res;
    518     else if (singlematch(ms, s, p, ep))
    519       s++;  /* try with one more repetition */
    520     else return NULL;
    521   }
    522 }
    523 
    524 
    525 static const char *start_capture (MatchState *ms, const char *s,
    526                                     const char *p, int what) {
    527   const char *res;
    528   int level = ms->level;
    529   if (level >= LUA_MAXCAPTURES) luaL_error(ms->L, "too many captures");
    530   ms->capture[level].init = s;
    531   ms->capture[level].len = what;
    532   ms->level = level+1;
    533   if ((res=match(ms, s, p)) == NULL)  /* match failed? */
    534     ms->level--;  /* undo capture */
    535   return res;
    536 }
    537 
    538 
    539 static const char *end_capture (MatchState *ms, const char *s,
    540                                   const char *p) {
    541   int l = capture_to_close(ms);
    542   const char *res;
    543   ms->capture[l].len = s - ms->capture[l].init;  /* close capture */
    544   if ((res = match(ms, s, p)) == NULL)  /* match failed? */
    545     ms->capture[l].len = CAP_UNFINISHED;  /* undo capture */
    546   return res;
    547 }
    548 
    549 
    550 static const char *match_capture (MatchState *ms, const char *s, int l) {
    551   size_t len;
    552   l = check_capture(ms, l);
    553   len = cast_sizet(ms->capture[l].len);
    554   if ((size_t)(ms->src_end-s) >= len &&
    555       memcmp(ms->capture[l].init, s, len) == 0)
    556     return s+len;
    557   else return NULL;
    558 }
    559 
    560 
    561 static const char *match (MatchState *ms, const char *s, const char *p) {
    562   if (l_unlikely(ms->matchdepth-- == 0))
    563     luaL_error(ms->L, "pattern too complex");
    564   init: /* using goto to optimize tail recursion */
    565   if (p != ms->p_end) {  /* end of pattern? */
    566     switch (*p) {
    567       case '(': {  /* start capture */
    568         if (*(p + 1) == ')')  /* position capture? */
    569           s = start_capture(ms, s, p + 2, CAP_POSITION);
    570         else
    571           s = start_capture(ms, s, p + 1, CAP_UNFINISHED);
    572         break;
    573       }
    574       case ')': {  /* end capture */
    575         s = end_capture(ms, s, p + 1);
    576         break;
    577       }
    578       case '$': {
    579         if ((p + 1) != ms->p_end)  /* is the '$' the last char in pattern? */
    580           goto dflt;  /* no; go to default */
    581         s = (s == ms->src_end) ? s : NULL;  /* check end of string */
    582         break;
    583       }
    584       case L_ESC: {  /* escaped sequences not in the format class[*+?-]? */
    585         switch (*(p + 1)) {
    586           case 'b': {  /* balanced string? */
    587             s = matchbalance(ms, s, p + 2);
    588             if (s != NULL) {
    589               p += 4; goto init;  /* return match(ms, s, p + 4); */
    590             }  /* else fail (s == NULL) */
    591             break;
    592           }
    593           case 'f': {  /* frontier? */
    594             const char *ep; char previous;
    595             p += 2;
    596             if (l_unlikely(*p != '['))
    597               luaL_error(ms->L, "missing '[' after '%%f' in pattern");
    598             ep = classend(ms, p);  /* points to what is next */
    599             previous = (s == ms->src_init) ? '\0' : *(s - 1);
    600             if (!matchbracketclass(cast_uchar(previous), p, ep - 1) &&
    601                matchbracketclass(cast_uchar(*s), p, ep - 1)) {
    602               p = ep; goto init;  /* return match(ms, s, ep); */
    603             }
    604             s = NULL;  /* match failed */
    605             break;
    606           }
    607           case '0': case '1': case '2': case '3':
    608           case '4': case '5': case '6': case '7':
    609           case '8': case '9': {  /* capture results (%0-%9)? */
    610             s = match_capture(ms, s, cast_uchar(*(p + 1)));
    611             if (s != NULL) {
    612               p += 2; goto init;  /* return match(ms, s, p + 2) */
    613             }
    614             break;
    615           }
    616           default: goto dflt;
    617         }
    618         break;
    619       }
    620       default: dflt: {  /* pattern class plus optional suffix */
    621         const char *ep = classend(ms, p);  /* points to optional suffix */
    622         /* does not match at least once? */
    623         if (!singlematch(ms, s, p, ep)) {
    624           if (*ep == '*' || *ep == '?' || *ep == '-') {  /* accept empty? */
    625             p = ep + 1; goto init;  /* return match(ms, s, ep + 1); */
    626           }
    627           else  /* '+' or no suffix */
    628             s = NULL;  /* fail */
    629         }
    630         else {  /* matched once */
    631           switch (*ep) {  /* handle optional suffix */
    632             case '?': {  /* optional */
    633               const char *res;
    634               if ((res = match(ms, s + 1, ep + 1)) != NULL)
    635                 s = res;
    636               else {
    637                 p = ep + 1; goto init;  /* else return match(ms, s, ep + 1); */
    638               }
    639               break;
    640             }
    641             case '+':  /* 1 or more repetitions */
    642               s++;  /* 1 match already done */
    643               /* FALLTHROUGH */
    644             case '*':  /* 0 or more repetitions */
    645               s = max_expand(ms, s, p, ep);
    646               break;
    647             case '-':  /* 0 or more repetitions (minimum) */
    648               s = min_expand(ms, s, p, ep);
    649               break;
    650             default:  /* no suffix */
    651               s++; p = ep; goto init;  /* return match(ms, s + 1, ep); */
    652           }
    653         }
    654         break;
    655       }
    656     }
    657   }
    658   ms->matchdepth++;
    659   return s;
    660 }
    661 
    662 
    663 
    664 static const char *lmemfind (const char *s1, size_t l1,
    665                                const char *s2, size_t l2) {
    666   if (l2 == 0) return s1;  /* empty strings are everywhere */
    667   else if (l2 > l1) return NULL;  /* avoids a negative 'l1' */
    668   else {
    669     const char *init;  /* to search for a '*s2' inside 's1' */
    670     l2--;  /* 1st char will be checked by 'memchr' */
    671     l1 = l1-l2;  /* 's2' cannot be found after that */
    672     while (l1 > 0 && (init = (const char *)memchr(s1, *s2, l1)) != NULL) {
    673       init++;   /* 1st char is already checked */
    674       if (memcmp(init, s2+1, l2) == 0)
    675         return init-1;
    676       else {  /* correct 'l1' and 's1' to try again */
    677         l1 -= ct_diff2sz(init - s1);
    678         s1 = init;
    679       }
    680     }
    681     return NULL;  /* not found */
    682   }
    683 }
    684 
    685 
    686 /*
    687 ** get information about the i-th capture. If there are no captures
    688 ** and 'i==0', return information about the whole match, which
    689 ** is the range 's'..'e'. If the capture is a string, return
    690 ** its length and put its address in '*cap'. If it is an integer
    691 ** (a position), push it on the stack and return CAP_POSITION.
    692 */
    693 static ptrdiff_t get_onecapture (MatchState *ms, int i, const char *s,
    694                               const char *e, const char **cap) {
    695   if (i >= ms->level) {
    696     if (l_unlikely(i != 0))
    697       luaL_error(ms->L, "invalid capture index %%%d", i + 1);
    698     *cap = s;
    699     return (e - s);
    700   }
    701   else {
    702     ptrdiff_t capl = ms->capture[i].len;
    703     *cap = ms->capture[i].init;
    704     if (l_unlikely(capl == CAP_UNFINISHED))
    705       luaL_error(ms->L, "unfinished capture");
    706     else if (capl == CAP_POSITION)
    707       lua_pushinteger(ms->L,
    708           ct_diff2S(ms->capture[i].init - ms->src_init) + 1);
    709     return capl;
    710   }
    711 }
    712 
    713 
    714 /*
    715 ** Push the i-th capture on the stack.
    716 */
    717 static void push_onecapture (MatchState *ms, int i, const char *s,
    718                                                     const char *e) {
    719   const char *cap;
    720   ptrdiff_t l = get_onecapture(ms, i, s, e, &cap);
    721   if (l != CAP_POSITION)
    722     lua_pushlstring(ms->L, cap, cast_sizet(l));
    723   /* else position was already pushed */
    724 }
    725 
    726 
    727 static int push_captures (MatchState *ms, const char *s, const char *e) {
    728   int i;
    729   int nlevels = (ms->level == 0 && s) ? 1 : ms->level;
    730   luaL_checkstack(ms->L, nlevels, "too many captures");
    731   for (i = 0; i < nlevels; i++)
    732     push_onecapture(ms, i, s, e);
    733   return nlevels;  /* number of strings pushed */
    734 }
    735 
    736 
    737 /* check whether pattern has no special characters */
    738 static int nospecials (const char *p, size_t l) {
    739   size_t upto = 0;
    740   do {
    741     if (strpbrk(p + upto, SPECIALS))
    742       return 0;  /* pattern has a special character */
    743     upto += strlen(p + upto) + 1;  /* may have more after \0 */
    744   } while (upto <= l);
    745   return 1;  /* no special chars found */
    746 }
    747 
    748 
    749 static void prepstate (MatchState *ms, lua_State *L,
    750                        const char *s, size_t ls, const char *p, size_t lp) {
    751   ms->L = L;
    752   ms->matchdepth = MAXCCALLS;
    753   ms->src_init = s;
    754   ms->src_end = s + ls;
    755   ms->p_end = p + lp;
    756 }
    757 
    758 
    759 static void reprepstate (MatchState *ms) {
    760   ms->level = 0;
    761   lua_assert(ms->matchdepth == MAXCCALLS);
    762 }
    763 
    764 
    765 static int str_find_aux (lua_State *L, int find) {
    766   size_t ls, lp;
    767   const char *s = luaL_checklstring(L, 1, &ls);
    768   const char *p = luaL_checklstring(L, 2, &lp);
    769   size_t init = posrelatI(luaL_optinteger(L, 3, 1), ls) - 1;
    770   if (init > ls) {  /* start after string's end? */
    771     luaL_pushfail(L);  /* cannot find anything */
    772     return 1;
    773   }
    774   /* explicit request or no special characters? */
    775   if (find && (lua_toboolean(L, 4) || nospecials(p, lp))) {
    776     /* do a plain search */
    777     const char *s2 = lmemfind(s + init, ls - init, p, lp);
    778     if (s2) {
    779       lua_pushinteger(L, ct_diff2S(s2 - s) + 1);
    780       lua_pushinteger(L, cast_st2S(ct_diff2sz(s2 - s) + lp));
    781       return 2;
    782     }
    783   }
    784   else {
    785     MatchState ms;
    786     const char *s1 = s + init;
    787     int anchor = (*p == '^');
    788     if (anchor) {
    789       p++; lp--;  /* skip anchor character */
    790     }
    791     prepstate(&ms, L, s, ls, p, lp);
    792     do {
    793       const char *res;
    794       reprepstate(&ms);
    795       if ((res=match(&ms, s1, p)) != NULL) {
    796         if (find) {
    797           lua_pushinteger(L, ct_diff2S(s1 - s) + 1);  /* start */
    798           lua_pushinteger(L, ct_diff2S(res - s));   /* end */
    799           return push_captures(&ms, NULL, 0) + 2;
    800         }
    801         else
    802           return push_captures(&ms, s1, res);
    803       }
    804     } while (s1++ < ms.src_end && !anchor);
    805   }
    806   luaL_pushfail(L);  /* not found */
    807   return 1;
    808 }
    809 
    810 
    811 static int str_find (lua_State *L) {
    812   return str_find_aux(L, 1);
    813 }
    814 
    815 
    816 static int str_match (lua_State *L) {
    817   return str_find_aux(L, 0);
    818 }
    819 
    820 
    821 /* state for 'gmatch' */
    822 typedef struct GMatchState {
    823   const char *src;  /* current position */
    824   const char *p;  /* pattern */
    825   const char *lastmatch;  /* end of last match */
    826   MatchState ms;  /* match state */
    827 } GMatchState;
    828 
    829 
    830 static int gmatch_aux (lua_State *L) {
    831   GMatchState *gm = (GMatchState *)lua_touserdata(L, lua_upvalueindex(3));
    832   const char *src;
    833   gm->ms.L = L;
    834   for (src = gm->src; src <= gm->ms.src_end; src++) {
    835     const char *e;
    836     reprepstate(&gm->ms);
    837     if ((e = match(&gm->ms, src, gm->p)) != NULL && e != gm->lastmatch) {
    838       gm->src = gm->lastmatch = e;
    839       return push_captures(&gm->ms, src, e);
    840     }
    841   }
    842   return 0;  /* not found */
    843 }
    844 
    845 
    846 static int gmatch (lua_State *L) {
    847   size_t ls, lp;
    848   const char *s = luaL_checklstring(L, 1, &ls);
    849   const char *p = luaL_checklstring(L, 2, &lp);
    850   size_t init = posrelatI(luaL_optinteger(L, 3, 1), ls) - 1;
    851   GMatchState *gm;
    852   lua_settop(L, 2);  /* keep strings on closure to avoid being collected */
    853   gm = (GMatchState *)lua_newuserdatauv(L, sizeof(GMatchState), 0);
    854   if (init > ls)  /* start after string's end? */
    855     init = ls + 1;  /* avoid overflows in 's + init' */
    856   prepstate(&gm->ms, L, s, ls, p, lp);
    857   gm->src = s + init; gm->p = p; gm->lastmatch = NULL;
    858   lua_pushcclosure(L, gmatch_aux, 3);
    859   return 1;
    860 }
    861 
    862 
    863 static void add_s (MatchState *ms, luaL_Buffer *b, const char *s,
    864                                                    const char *e) {
    865   size_t l;
    866   lua_State *L = ms->L;
    867   const char *news = lua_tolstring(L, 3, &l);
    868   const char *p;
    869   while ((p = (char *)memchr(news, L_ESC, l)) != NULL) {
    870     luaL_addlstring(b, news, ct_diff2sz(p - news));
    871     p++;  /* skip ESC */
    872     if (*p == L_ESC)  /* '%%' */
    873       luaL_addchar(b, *p);
    874     else if (*p == '0')  /* '%0' */
    875         luaL_addlstring(b, s, ct_diff2sz(e - s));
    876     else if (isdigit(cast_uchar(*p))) {  /* '%n' */
    877       const char *cap;
    878       ptrdiff_t resl = get_onecapture(ms, *p - '1', s, e, &cap);
    879       if (resl == CAP_POSITION)
    880         luaL_addvalue(b);  /* add position to accumulated result */
    881       else
    882         luaL_addlstring(b, cap, cast_sizet(resl));
    883     }
    884     else
    885       luaL_error(L, "invalid use of '%c' in replacement string", L_ESC);
    886     l -= ct_diff2sz(p + 1 - news);
    887     news = p + 1;
    888   }
    889   luaL_addlstring(b, news, l);
    890 }
    891 
    892 
    893 /*
    894 ** Add the replacement value to the string buffer 'b'.
    895 ** Return true if the original string was changed. (Function calls and
    896 ** table indexing resulting in nil or false do not change the subject.)
    897 */
    898 static int add_value (MatchState *ms, luaL_Buffer *b, const char *s,
    899                                       const char *e, int tr) {
    900   lua_State *L = ms->L;
    901   switch (tr) {
    902     case LUA_TFUNCTION: {  /* call the function */
    903       int n;
    904       lua_pushvalue(L, 3);  /* push the function */
    905       n = push_captures(ms, s, e);  /* all captures as arguments */
    906       lua_call(L, n, 1);  /* call it */
    907       break;
    908     }
    909     case LUA_TTABLE: {  /* index the table */
    910       push_onecapture(ms, 0, s, e);  /* first capture is the index */
    911       lua_gettable(L, 3);
    912       break;
    913     }
    914     default: {  /* LUA_TNUMBER or LUA_TSTRING */
    915       add_s(ms, b, s, e);  /* add value to the buffer */
    916       return 1;  /* something changed */
    917     }
    918   }
    919   if (!lua_toboolean(L, -1)) {  /* nil or false? */
    920     lua_pop(L, 1);  /* remove value */
    921     luaL_addlstring(b, s, ct_diff2sz(e - s));  /* keep original text */
    922     return 0;  /* no changes */
    923   }
    924   else if (l_unlikely(!lua_isstring(L, -1)))
    925     return luaL_error(L, "invalid replacement value (a %s)",
    926                          luaL_typename(L, -1));
    927   else {
    928     luaL_addvalue(b);  /* add result to accumulator */
    929     return 1;  /* something changed */
    930   }
    931 }
    932 
    933 
    934 static int str_gsub (lua_State *L) {
    935   size_t srcl, lp;
    936   const char *src = luaL_checklstring(L, 1, &srcl);  /* subject */
    937   const char *p = luaL_checklstring(L, 2, &lp);  /* pattern */
    938   const char *lastmatch = NULL;  /* end of last match */
    939   int tr = lua_type(L, 3);  /* replacement type */
    940   /* max replacements */
    941   lua_Integer max_s = luaL_optinteger(L, 4, cast_st2S(srcl) + 1);
    942   int anchor = (*p == '^');
    943   lua_Integer n = 0;  /* replacement count */
    944   int changed = 0;  /* change flag */
    945   MatchState ms;
    946   luaL_Buffer b;
    947   luaL_argexpected(L, tr == LUA_TNUMBER || tr == LUA_TSTRING ||
    948                    tr == LUA_TFUNCTION || tr == LUA_TTABLE, 3,
    949                       "string/function/table");
    950   luaL_buffinit(L, &b);
    951   if (anchor) {
    952     p++; lp--;  /* skip anchor character */
    953   }
    954   prepstate(&ms, L, src, srcl, p, lp);
    955   while (n < max_s) {
    956     const char *e;
    957     reprepstate(&ms);  /* (re)prepare state for new match */
    958     if ((e = match(&ms, src, p)) != NULL && e != lastmatch) {  /* match? */
    959       n++;
    960       changed = add_value(&ms, &b, src, e, tr) | changed;
    961       src = lastmatch = e;
    962     }
    963     else if (src < ms.src_end)  /* otherwise, skip one character */
    964       luaL_addchar(&b, *src++);
    965     else break;  /* end of subject */
    966     if (anchor) break;
    967   }
    968   if (!changed)  /* no changes? */
    969     lua_pushvalue(L, 1);  /* return original string */
    970   else {  /* something changed */
    971     luaL_addlstring(&b, src, ct_diff2sz(ms.src_end - src));
    972     luaL_pushresult(&b);  /* create and return new string */
    973   }
    974   lua_pushinteger(L, n);  /* number of substitutions */
    975   return 2;
    976 }
    977 
    978 /* }====================================================== */
    979 
    980 
    981 
    982 /*
    983 ** {======================================================
    984 ** STRING FORMAT
    985 ** =======================================================
    986 */
    987 
    988 #if !defined(lua_number2strx)	/* { */
    989 
    990 /*
    991 ** Hexadecimal floating-point formatter
    992 */
    993 
    994 #define SIZELENMOD	(sizeof(LUA_NUMBER_FRMLEN)/sizeof(char))
    995 
    996 
    997 /*
    998 ** Number of bits that goes into the first digit. It can be any value
    999 ** between 1 and 4; the following definition tries to align the number
   1000 ** to nibble boundaries by making what is left after that first digit a
   1001 ** multiple of 4.
   1002 */
   1003 #define L_NBFD		((l_floatatt(MANT_DIG) - 1)%4 + 1)
   1004 
   1005 
   1006 /*
   1007 ** Add integer part of 'x' to buffer and return new 'x'
   1008 */
   1009 static lua_Number adddigit (char *buff, unsigned n, lua_Number x) {
   1010   lua_Number dd = l_mathop(floor)(x);  /* get integer part from 'x' */
   1011   int d = (int)dd;
   1012   buff[n] = cast_char(d < 10 ? d + '0' : d - 10 + 'a');  /* add to buffer */
   1013   return x - dd;  /* return what is left */
   1014 }
   1015 
   1016 
   1017 static int num2straux (char *buff, unsigned sz, lua_Number x) {
   1018   /* if 'inf' or 'NaN', format it like '%g' */
   1019   if (x != x || x == (lua_Number)HUGE_VAL || x == -(lua_Number)HUGE_VAL)
   1020     return l_sprintf(buff, sz, LUA_NUMBER_FMT, (LUAI_UACNUMBER)x);
   1021   else if (x == 0) {  /* can be -0... */
   1022     /* create "0" or "-0" followed by exponent */
   1023     return l_sprintf(buff, sz, LUA_NUMBER_FMT "x0p+0", (LUAI_UACNUMBER)x);
   1024   }
   1025   else {
   1026     int e;
   1027     lua_Number m = l_mathop(frexp)(x, &e);  /* 'x' fraction and exponent */
   1028     unsigned n = 0;  /* character count */
   1029     if (m < 0) {  /* is number negative? */
   1030       buff[n++] = '-';  /* add sign */
   1031       m = -m;  /* make it positive */
   1032     }
   1033     buff[n++] = '0'; buff[n++] = 'x';  /* add "0x" */
   1034     m = adddigit(buff, n++, m * (1 << L_NBFD));  /* add first digit */
   1035     e -= L_NBFD;  /* this digit goes before the radix point */
   1036     if (m > 0) {  /* more digits? */
   1037       buff[n++] = lua_getlocaledecpoint();  /* add radix point */
   1038       do {  /* add as many digits as needed */
   1039         m = adddigit(buff, n++, m * 16);
   1040       } while (m > 0);
   1041     }
   1042     n += cast_uint(l_sprintf(buff + n, sz - n, "p%+d", e));  /* add exponent */
   1043     lua_assert(n < sz);
   1044     return cast_int(n);
   1045   }
   1046 }
   1047 
   1048 
   1049 static int lua_number2strx (lua_State *L, char *buff, unsigned sz,
   1050                             const char *fmt, lua_Number x) {
   1051   int n = num2straux(buff, sz, x);
   1052   if (fmt[SIZELENMOD] == 'A') {
   1053     int i;
   1054     for (i = 0; i < n; i++)
   1055       buff[i] = cast_char(toupper(cast_uchar(buff[i])));
   1056   }
   1057   else if (l_unlikely(fmt[SIZELENMOD] != 'a'))
   1058     return luaL_error(L, "modifiers for format '%%a'/'%%A' not implemented");
   1059   return n;
   1060 }
   1061 
   1062 #endif				/* } */
   1063 
   1064 
   1065 /*
   1066 ** Maximum size for items formatted with '%f'. This size is produced
   1067 ** by format('%.99f', -maxfloat), and is equal to 99 + 3 ('-', '.',
   1068 ** and '\0') + number of decimal digits to represent maxfloat (which
   1069 ** is maximum exponent + 1). (99+3+1, adding some extra, 110)
   1070 */
   1071 #define MAX_ITEMF	(110 + l_floatatt(MAX_10_EXP))
   1072 
   1073 
   1074 /*
   1075 ** All formats except '%f' do not need that large limit.  The other
   1076 ** float formats use exponents, so that they fit in the 99 limit for
   1077 ** significant digits; 's' for large strings and 'q' add items directly
   1078 ** to the buffer; all integer formats also fit in the 99 limit.  The
   1079 ** worst case are floats: they may need 99 significant digits, plus
   1080 ** '0x', '-', '.', 'e+XXXX', and '\0'. Adding some extra, 120.
   1081 */
   1082 #define MAX_ITEM	120
   1083 
   1084 
   1085 /* valid flags in a format specification */
   1086 #if !defined(L_FMTFLAGSF)
   1087 
   1088 /* valid flags for a, A, e, E, f, F, g, and G conversions */
   1089 #define L_FMTFLAGSF	"-+#0 "
   1090 
   1091 /* valid flags for o, x, and X conversions */
   1092 #define L_FMTFLAGSX	"-#0"
   1093 
   1094 /* valid flags for d and i conversions */
   1095 #define L_FMTFLAGSI	"-+0 "
   1096 
   1097 /* valid flags for u conversions */
   1098 #define L_FMTFLAGSU	"-0"
   1099 
   1100 /* valid flags for c, p, and s conversions */
   1101 #define L_FMTFLAGSC	"-"
   1102 
   1103 #endif
   1104 
   1105 
   1106 /*
   1107 ** Maximum size of each format specification (such as "%-099.99d"):
   1108 ** Initial '%', flags (up to 5), width (2), period, precision (2),
   1109 ** length modifier (8), conversion specifier, and final '\0', plus some
   1110 ** extra.
   1111 */
   1112 #define MAX_FORMAT	32
   1113 
   1114 
   1115 static void addquoted (luaL_Buffer *b, const char *s, size_t len) {
   1116   luaL_addchar(b, '"');
   1117   while (len--) {
   1118     if (*s == '"' || *s == '\\' || *s == '\n') {
   1119       luaL_addchar(b, '\\');
   1120       luaL_addchar(b, *s);
   1121     }
   1122     else if (iscntrl(cast_uchar(*s))) {
   1123       char buff[10];
   1124       if (!isdigit(cast_uchar(*(s+1))))
   1125         l_sprintf(buff, sizeof(buff), "\\%d", (int)cast_uchar(*s));
   1126       else
   1127         l_sprintf(buff, sizeof(buff), "\\%03d", (int)cast_uchar(*s));
   1128       luaL_addstring(b, buff);
   1129     }
   1130     else
   1131       luaL_addchar(b, *s);
   1132     s++;
   1133   }
   1134   luaL_addchar(b, '"');
   1135 }
   1136 
   1137 
   1138 /*
   1139 ** Serialize a floating-point number in such a way that it can be
   1140 ** scanned back by Lua. Use hexadecimal format for "common" numbers
   1141 ** (to preserve precision); inf, -inf, and NaN are handled separately.
   1142 ** (NaN cannot be expressed as a numeral, so we write '(0/0)' for it.)
   1143 */
   1144 static int quotefloat (lua_State *L, char *buff, lua_Number n) {
   1145   const char *s;  /* for the fixed representations */
   1146   if (n == (lua_Number)HUGE_VAL)  /* inf? */
   1147     s = "1e9999";
   1148   else if (n == -(lua_Number)HUGE_VAL)  /* -inf? */
   1149     s = "-1e9999";
   1150   else if (n != n)  /* NaN? */
   1151     s = "(0/0)";
   1152   else {  /* format number as hexadecimal */
   1153     int  nb = lua_number2strx(L, buff, MAX_ITEM,
   1154                                  "%" LUA_NUMBER_FRMLEN "a", n);
   1155     /* ensures that 'buff' string uses a dot as the radix character */
   1156     if (memchr(buff, '.', cast_uint(nb)) == NULL) {  /* no dot? */
   1157       char point = lua_getlocaledecpoint();  /* try locale point */
   1158       char *ppoint = (char *)memchr(buff, point, cast_uint(nb));
   1159       if (ppoint) *ppoint = '.';  /* change it to a dot */
   1160     }
   1161     return nb;
   1162   }
   1163   /* for the fixed representations */
   1164   return l_sprintf(buff, MAX_ITEM, "%s", s);
   1165 }
   1166 
   1167 
   1168 static void addliteral (lua_State *L, luaL_Buffer *b, int arg) {
   1169   switch (lua_type(L, arg)) {
   1170     case LUA_TSTRING: {
   1171       size_t len;
   1172       const char *s = lua_tolstring(L, arg, &len);
   1173       addquoted(b, s, len);
   1174       break;
   1175     }
   1176     case LUA_TNUMBER: {
   1177       char *buff = luaL_prepbuffsize(b, MAX_ITEM);
   1178       int nb;
   1179       if (!lua_isinteger(L, arg))  /* float? */
   1180         nb = quotefloat(L, buff, lua_tonumber(L, arg));
   1181       else {  /* integers */
   1182         lua_Integer n = lua_tointeger(L, arg);
   1183         const char *format = (n == LUA_MININTEGER)  /* corner case? */
   1184                            ? "0x%" LUA_INTEGER_FRMLEN "x"  /* use hex */
   1185                            : LUA_INTEGER_FMT;  /* else use default format */
   1186         nb = l_sprintf(buff, MAX_ITEM, format, (LUAI_UACINT)n);
   1187       }
   1188       luaL_addsize(b, cast_uint(nb));
   1189       break;
   1190     }
   1191     case LUA_TNIL: case LUA_TBOOLEAN: {
   1192       luaL_tolstring(L, arg, NULL);
   1193       luaL_addvalue(b);
   1194       break;
   1195     }
   1196     default: {
   1197       luaL_argerror(L, arg, "value has no literal form");
   1198     }
   1199   }
   1200 }
   1201 
   1202 
   1203 static const char *get2digits (const char *s) {
   1204   if (isdigit(cast_uchar(*s))) {
   1205     s++;
   1206     if (isdigit(cast_uchar(*s))) s++;  /* (2 digits at most) */
   1207   }
   1208   return s;
   1209 }
   1210 
   1211 
   1212 /*
   1213 ** Check whether a conversion specification is valid. When called,
   1214 ** first character in 'form' must be '%' and last character must
   1215 ** be a valid conversion specifier. 'flags' are the accepted flags;
   1216 ** 'precision' signals whether to accept a precision.
   1217 */
   1218 static void checkformat (lua_State *L, const char *form, const char *flags,
   1219                                        int precision) {
   1220   const char *spec = form + 1;  /* skip '%' */
   1221   spec += strspn(spec, flags);  /* skip flags */
   1222   if (*spec != '0') {  /* a width cannot start with '0' */
   1223     spec = get2digits(spec);  /* skip width */
   1224     if (*spec == '.' && precision) {
   1225       spec++;
   1226       spec = get2digits(spec);  /* skip precision */
   1227     }
   1228   }
   1229   if (!isalpha(cast_uchar(*spec)))  /* did not go to the end? */
   1230     luaL_error(L, "invalid conversion specification: '%s'", form);
   1231 }
   1232 
   1233 
   1234 /*
   1235 ** Get a conversion specification and copy it to 'form'.
   1236 ** Return the address of its last character.
   1237 */
   1238 static const char *getformat (lua_State *L, const char *strfrmt,
   1239                                             char *form) {
   1240   /* spans flags, width, and precision ('0' is included as a flag) */
   1241   size_t len = strspn(strfrmt, L_FMTFLAGSF "123456789.");
   1242   len++;  /* adds following character (should be the specifier) */
   1243   /* still needs space for '%', '\0', plus a length modifier */
   1244   if (len >= MAX_FORMAT - 10)
   1245     luaL_error(L, "invalid format (too long)");
   1246   *(form++) = '%';
   1247   memcpy(form, strfrmt, len * sizeof(char));
   1248   *(form + len) = '\0';
   1249   return strfrmt + len - 1;
   1250 }
   1251 
   1252 
   1253 /*
   1254 ** add length modifier into formats
   1255 */
   1256 static void addlenmod (char *form, const char *lenmod) {
   1257   size_t l = strlen(form);
   1258   size_t lm = strlen(lenmod);
   1259   char spec = form[l - 1];
   1260   strcpy(form + l - 1, lenmod);
   1261   form[l + lm - 1] = spec;
   1262   form[l + lm] = '\0';
   1263 }
   1264 
   1265 
   1266 static int str_format (lua_State *L) {
   1267   int top = lua_gettop(L);
   1268   int arg = 1;
   1269   size_t sfl;
   1270   const char *strfrmt = luaL_checklstring(L, arg, &sfl);
   1271   const char *strfrmt_end = strfrmt+sfl;
   1272   const char *flags;
   1273   luaL_Buffer b;
   1274   luaL_buffinit(L, &b);
   1275   while (strfrmt < strfrmt_end) {
   1276     if (*strfrmt != L_ESC)
   1277       luaL_addchar(&b, *strfrmt++);
   1278     else if (*++strfrmt == L_ESC)
   1279       luaL_addchar(&b, *strfrmt++);  /* %% */
   1280     else { /* format item */
   1281       char form[MAX_FORMAT];  /* to store the format ('%...') */
   1282       unsigned maxitem = MAX_ITEM;  /* maximum length for the result */
   1283       char *buff = luaL_prepbuffsize(&b, maxitem);  /* to put result */
   1284       int nb = 0;  /* number of bytes in result */
   1285       if (++arg > top)
   1286         return luaL_argerror(L, arg, "no value");
   1287       strfrmt = getformat(L, strfrmt, form);
   1288       switch (*strfrmt++) {
   1289         case 'c': {
   1290           checkformat(L, form, L_FMTFLAGSC, 0);
   1291           nb = l_sprintf(buff, maxitem, form, (int)luaL_checkinteger(L, arg));
   1292           break;
   1293         }
   1294         case 'd': case 'i':
   1295           flags = L_FMTFLAGSI;
   1296           goto intcase;
   1297         case 'u':
   1298           flags = L_FMTFLAGSU;
   1299           goto intcase;
   1300         case 'o': case 'x': case 'X':
   1301           flags = L_FMTFLAGSX;
   1302          intcase: {
   1303           lua_Integer n = luaL_checkinteger(L, arg);
   1304           checkformat(L, form, flags, 1);
   1305           addlenmod(form, LUA_INTEGER_FRMLEN);
   1306           nb = l_sprintf(buff, maxitem, form, (LUAI_UACINT)n);
   1307           break;
   1308         }
   1309         case 'a': case 'A':
   1310           checkformat(L, form, L_FMTFLAGSF, 1);
   1311           addlenmod(form, LUA_NUMBER_FRMLEN);
   1312           nb = lua_number2strx(L, buff, maxitem, form,
   1313                                   luaL_checknumber(L, arg));
   1314           break;
   1315         case 'f':
   1316           maxitem = MAX_ITEMF;  /* extra space for '%f' */
   1317           buff = luaL_prepbuffsize(&b, maxitem);
   1318           /* FALLTHROUGH */
   1319         case 'e': case 'E': case 'g': case 'G': {
   1320           lua_Number n = luaL_checknumber(L, arg);
   1321           checkformat(L, form, L_FMTFLAGSF, 1);
   1322           addlenmod(form, LUA_NUMBER_FRMLEN);
   1323           nb = l_sprintf(buff, maxitem, form, (LUAI_UACNUMBER)n);
   1324           break;
   1325         }
   1326         case 'p': {
   1327           const void *p = lua_topointer(L, arg);
   1328           checkformat(L, form, L_FMTFLAGSC, 0);
   1329           if (p == NULL) {  /* avoid calling 'printf' with argument NULL */
   1330             p = "(null)";  /* result */
   1331             form[strlen(form) - 1] = 's';  /* format it as a string */
   1332           }
   1333           nb = l_sprintf(buff, maxitem, form, p);
   1334           break;
   1335         }
   1336         case 'q': {
   1337           if (form[2] != '\0')  /* modifiers? */
   1338             return luaL_error(L, "specifier '%%q' cannot have modifiers");
   1339           addliteral(L, &b, arg);
   1340           break;
   1341         }
   1342         case 's': {
   1343           size_t l;
   1344           const char *s = luaL_tolstring(L, arg, &l);
   1345           if (form[2] == '\0')  /* no modifiers? */
   1346             luaL_addvalue(&b);  /* keep entire string */
   1347           else {
   1348             luaL_argcheck(L, l == strlen(s), arg, "string contains zeros");
   1349             checkformat(L, form, L_FMTFLAGSC, 1);
   1350             if (strchr(form, '.') == NULL && l >= 100) {
   1351               /* no precision and string is too long to be formatted */
   1352               luaL_addvalue(&b);  /* keep entire string */
   1353             }
   1354             else {  /* format the string into 'buff' */
   1355               nb = l_sprintf(buff, maxitem, form, s);
   1356               lua_pop(L, 1);  /* remove result from 'luaL_tolstring' */
   1357             }
   1358           }
   1359           break;
   1360         }
   1361         default: {  /* also treat cases 'pnLlh' */
   1362           return luaL_error(L, "invalid conversion '%s' to 'format'", form);
   1363         }
   1364       }
   1365       lua_assert(cast_uint(nb) < maxitem);
   1366       luaL_addsize(&b, cast_uint(nb));
   1367     }
   1368   }
   1369   luaL_pushresult(&b);
   1370   return 1;
   1371 }
   1372 
   1373 /* }====================================================== */
   1374 
   1375 
   1376 /*
   1377 ** {======================================================
   1378 ** PACK/UNPACK
   1379 ** =======================================================
   1380 */
   1381 
   1382 
   1383 /* value used for padding */
   1384 #if !defined(LUAL_PACKPADBYTE)
   1385 #define LUAL_PACKPADBYTE		0x00
   1386 #endif
   1387 
   1388 /* maximum size for the binary representation of an integer */
   1389 #define MAXINTSIZE	16
   1390 
   1391 /* number of bits in a character */
   1392 #define NB	CHAR_BIT
   1393 
   1394 /* mask for one character (NB 1's) */
   1395 #define MC	((1 << NB) - 1)
   1396 
   1397 /* size of a lua_Integer */
   1398 #define SZINT	((int)sizeof(lua_Integer))
   1399 
   1400 
   1401 /* dummy union to get native endianness */
   1402 static const union {
   1403   int dummy;
   1404   char little;  /* true iff machine is little endian */
   1405 } nativeendian = {1};
   1406 
   1407 
   1408 /*
   1409 ** information to pack/unpack stuff
   1410 */
   1411 typedef struct Header {
   1412   lua_State *L;
   1413   int islittle;
   1414   unsigned maxalign;
   1415 } Header;
   1416 
   1417 
   1418 /*
   1419 ** options for pack/unpack
   1420 */
   1421 typedef enum KOption {
   1422   Kint,		/* signed integers */
   1423   Kuint,	/* unsigned integers */
   1424   Kfloat,	/* single-precision floating-point numbers */
   1425   Knumber,	/* Lua "native" floating-point numbers */
   1426   Kdouble,	/* double-precision floating-point numbers */
   1427   Kchar,	/* fixed-length strings */
   1428   Kstring,	/* strings with prefixed length */
   1429   Kzstr,	/* zero-terminated strings */
   1430   Kpadding,	/* padding */
   1431   Kpaddalign,	/* padding for alignment */
   1432   Knop		/* no-op (configuration or spaces) */
   1433 } KOption;
   1434 
   1435 
   1436 /*
   1437 ** Read an integer numeral from string 'fmt' or return 'df' if
   1438 ** there is no numeral
   1439 */
   1440 static int digit (int c) { return '0' <= c && c <= '9'; }
   1441 
   1442 static size_t getnum (const char **fmt, size_t df) {
   1443   if (!digit(**fmt))  /* no number? */
   1444     return df;  /* return default value */
   1445   else {
   1446     size_t a = 0;
   1447     do {
   1448       a = a*10 + cast_uint(*((*fmt)++) - '0');
   1449     } while (digit(**fmt) && a <= (MAX_SIZE - 9)/10);
   1450     return a;
   1451   }
   1452 }
   1453 
   1454 
   1455 /*
   1456 ** Read an integer numeral and raises an error if it is larger
   1457 ** than the maximum size of integers.
   1458 */
   1459 static unsigned getnumlimit (Header *h, const char **fmt, size_t df) {
   1460   size_t sz = getnum(fmt, df);
   1461   if (l_unlikely((sz - 1u) >= MAXINTSIZE))
   1462     return cast_uint(luaL_error(h->L,
   1463                "integral size (%d) out of limits [1,%d]", sz, MAXINTSIZE));
   1464   return cast_uint(sz);
   1465 }
   1466 
   1467 
   1468 /*
   1469 ** Initialize Header
   1470 */
   1471 static void initheader (lua_State *L, Header *h) {
   1472   h->L = L;
   1473   h->islittle = nativeendian.little;
   1474   h->maxalign = 1;
   1475 }
   1476 
   1477 
   1478 /*
   1479 ** Read and classify next option. 'size' is filled with option's size.
   1480 */
   1481 static KOption getoption (Header *h, const char **fmt, size_t *size) {
   1482   /* dummy structure to get native alignment requirements */
   1483   struct cD { char c; union { LUAI_MAXALIGN; } u; };
   1484   int opt = *((*fmt)++);
   1485   *size = 0;  /* default */
   1486   switch (opt) {
   1487     case 'b': *size = sizeof(char); return Kint;
   1488     case 'B': *size = sizeof(char); return Kuint;
   1489     case 'h': *size = sizeof(short); return Kint;
   1490     case 'H': *size = sizeof(short); return Kuint;
   1491     case 'l': *size = sizeof(long); return Kint;
   1492     case 'L': *size = sizeof(long); return Kuint;
   1493     case 'j': *size = sizeof(lua_Integer); return Kint;
   1494     case 'J': *size = sizeof(lua_Integer); return Kuint;
   1495     case 'T': *size = sizeof(size_t); return Kuint;
   1496     case 'f': *size = sizeof(float); return Kfloat;
   1497     case 'n': *size = sizeof(lua_Number); return Knumber;
   1498     case 'd': *size = sizeof(double); return Kdouble;
   1499     case 'i': *size = getnumlimit(h, fmt, sizeof(int)); return Kint;
   1500     case 'I': *size = getnumlimit(h, fmt, sizeof(int)); return Kuint;
   1501     case 's': *size = getnumlimit(h, fmt, sizeof(size_t)); return Kstring;
   1502     case 'c':
   1503       *size = getnum(fmt, cast_sizet(-1));
   1504       if (l_unlikely(*size == cast_sizet(-1)))
   1505         luaL_error(h->L, "missing size for format option 'c'");
   1506       return Kchar;
   1507     case 'z': return Kzstr;
   1508     case 'x': *size = 1; return Kpadding;
   1509     case 'X': return Kpaddalign;
   1510     case ' ': break;
   1511     case '<': h->islittle = 1; break;
   1512     case '>': h->islittle = 0; break;
   1513     case '=': h->islittle = nativeendian.little; break;
   1514     case '!': {
   1515       const size_t maxalign = offsetof(struct cD, u);
   1516       h->maxalign = getnumlimit(h, fmt, maxalign);
   1517       break;
   1518     }
   1519     default: luaL_error(h->L, "invalid format option '%c'", opt);
   1520   }
   1521   return Knop;
   1522 }
   1523 
   1524 
   1525 /*
   1526 ** Read, classify, and fill other details about the next option.
   1527 ** 'psize' is filled with option's size, 'notoalign' with its
   1528 ** alignment requirements.
   1529 ** Local variable 'size' gets the size to be aligned. (Kpadal option
   1530 ** always gets its full alignment, other options are limited by
   1531 ** the maximum alignment ('maxalign'). Kchar option needs no alignment
   1532 ** despite its size.
   1533 */
   1534 static KOption getdetails (Header *h, size_t totalsize, const char **fmt,
   1535                            size_t *psize, unsigned *ntoalign) {
   1536   KOption opt = getoption(h, fmt, psize);
   1537   size_t align = *psize;  /* usually, alignment follows size */
   1538   if (opt == Kpaddalign) {  /* 'X' gets alignment from following option */
   1539     if (**fmt == '\0' || getoption(h, fmt, &align) == Kchar || align == 0)
   1540       luaL_argerror(h->L, 1, "invalid next option for option 'X'");
   1541   }
   1542   if (align <= 1 || opt == Kchar)  /* need no alignment? */
   1543     *ntoalign = 0;
   1544   else {
   1545     if (align > h->maxalign)  /* enforce maximum alignment */
   1546       align = h->maxalign;
   1547     if (l_unlikely(!ispow2(align)))  /* not a power of 2? */
   1548       luaL_argerror(h->L, 1, "format asks for alignment not power of 2");
   1549     else {
   1550       /* 'szmoda' = totalsize % align */
   1551       unsigned szmoda = cast_uint(totalsize & (align - 1));
   1552       *ntoalign = cast_uint((align - szmoda) & (align - 1));
   1553     }
   1554   }
   1555   return opt;
   1556 }
   1557 
   1558 
   1559 /*
   1560 ** Pack integer 'n' with 'size' bytes and 'islittle' endianness.
   1561 ** The final 'if' handles the case when 'size' is larger than
   1562 ** the size of a Lua integer, correcting the extra sign-extension
   1563 ** bytes if necessary (by default they would be zeros).
   1564 */
   1565 static void packint (luaL_Buffer *b, lua_Unsigned n,
   1566                      int islittle, unsigned size, int neg) {
   1567   char *buff = luaL_prepbuffsize(b, size);
   1568   unsigned i;
   1569   buff[islittle ? 0 : size - 1] = (char)(n & MC);  /* first byte */
   1570   for (i = 1; i < size; i++) {
   1571     n >>= NB;
   1572     buff[islittle ? i : size - 1 - i] = (char)(n & MC);
   1573   }
   1574   if (neg && size > SZINT) {  /* negative number need sign extension? */
   1575     for (i = SZINT; i < size; i++)  /* correct extra bytes */
   1576       buff[islittle ? i : size - 1 - i] = (char)MC;
   1577   }
   1578   luaL_addsize(b, size);  /* add result to buffer */
   1579 }
   1580 
   1581 
   1582 /*
   1583 ** Copy 'size' bytes from 'src' to 'dest', correcting endianness if
   1584 ** given 'islittle' is different from native endianness.
   1585 */
   1586 static void copywithendian (char *dest, const char *src,
   1587                             unsigned size, int islittle) {
   1588   if (islittle == nativeendian.little)
   1589     memcpy(dest, src, size);
   1590   else {
   1591     dest += size - 1;
   1592     while (size-- != 0)
   1593       *(dest--) = *(src++);
   1594   }
   1595 }
   1596 
   1597 
   1598 static int str_pack (lua_State *L) {
   1599   luaL_Buffer b;
   1600   Header h;
   1601   const char *fmt = luaL_checkstring(L, 1);  /* format string */
   1602   int arg = 1;  /* current argument to pack */
   1603   size_t totalsize = 0;  /* accumulate total size of result */
   1604   initheader(L, &h);
   1605   lua_pushnil(L);  /* mark to separate arguments from string buffer */
   1606   luaL_buffinit(L, &b);
   1607   while (*fmt != '\0') {
   1608     unsigned ntoalign;
   1609     size_t size;
   1610     KOption opt = getdetails(&h, totalsize, &fmt, &size, &ntoalign);
   1611     luaL_argcheck(L, size + ntoalign <= MAX_SIZE - totalsize, arg,
   1612                      "result too long");
   1613     totalsize += ntoalign + size;
   1614     while (ntoalign-- > 0)
   1615      luaL_addchar(&b, LUAL_PACKPADBYTE);  /* fill alignment */
   1616     arg++;
   1617     switch (opt) {
   1618       case Kint: {  /* signed integers */
   1619         lua_Integer n = luaL_checkinteger(L, arg);
   1620         if (size < SZINT) {  /* need overflow check? */
   1621           lua_Integer lim = (lua_Integer)1 << ((size * NB) - 1);
   1622           luaL_argcheck(L, -lim <= n && n < lim, arg, "integer overflow");
   1623         }
   1624         packint(&b, (lua_Unsigned)n, h.islittle, cast_uint(size), (n < 0));
   1625         break;
   1626       }
   1627       case Kuint: {  /* unsigned integers */
   1628         lua_Integer n = luaL_checkinteger(L, arg);
   1629         if (size < SZINT)  /* need overflow check? */
   1630           luaL_argcheck(L, (lua_Unsigned)n < ((lua_Unsigned)1 << (size * NB)),
   1631                            arg, "unsigned overflow");
   1632         packint(&b, (lua_Unsigned)n, h.islittle, cast_uint(size), 0);
   1633         break;
   1634       }
   1635       case Kfloat: {  /* C float */
   1636         float f = (float)luaL_checknumber(L, arg);  /* get argument */
   1637         char *buff = luaL_prepbuffsize(&b, sizeof(f));
   1638         /* move 'f' to final result, correcting endianness if needed */
   1639         copywithendian(buff, (char *)&f, sizeof(f), h.islittle);
   1640         luaL_addsize(&b, size);
   1641         break;
   1642       }
   1643       case Knumber: {  /* Lua float */
   1644         lua_Number f = luaL_checknumber(L, arg);  /* get argument */
   1645         char *buff = luaL_prepbuffsize(&b, sizeof(f));
   1646         /* move 'f' to final result, correcting endianness if needed */
   1647         copywithendian(buff, (char *)&f, sizeof(f), h.islittle);
   1648         luaL_addsize(&b, size);
   1649         break;
   1650       }
   1651       case Kdouble: {  /* C double */
   1652         double f = (double)luaL_checknumber(L, arg);  /* get argument */
   1653         char *buff = luaL_prepbuffsize(&b, sizeof(f));
   1654         /* move 'f' to final result, correcting endianness if needed */
   1655         copywithendian(buff, (char *)&f, sizeof(f), h.islittle);
   1656         luaL_addsize(&b, size);
   1657         break;
   1658       }
   1659       case Kchar: {  /* fixed-size string */
   1660         size_t len;
   1661         const char *s = luaL_checklstring(L, arg, &len);
   1662         luaL_argcheck(L, len <= size, arg, "string longer than given size");
   1663         luaL_addlstring(&b, s, len);  /* add string */
   1664         if (len < size) {  /* does it need padding? */
   1665           size_t psize = size - len;  /* pad size */
   1666           char *buff = luaL_prepbuffsize(&b, psize);
   1667           memset(buff, LUAL_PACKPADBYTE, psize);
   1668           luaL_addsize(&b, psize);
   1669         }
   1670         break;
   1671       }
   1672       case Kstring: {  /* strings with length count */
   1673         size_t len;
   1674         const char *s = luaL_checklstring(L, arg, &len);
   1675         luaL_argcheck(L, size >= sizeof(lua_Unsigned) ||
   1676                          len < ((lua_Unsigned)1 << (size * NB)),
   1677                          arg, "string length does not fit in given size");
   1678         /* pack length */
   1679         packint(&b, (lua_Unsigned)len, h.islittle, cast_uint(size), 0);
   1680         luaL_addlstring(&b, s, len);
   1681         totalsize += len;
   1682         break;
   1683       }
   1684       case Kzstr: {  /* zero-terminated string */
   1685         size_t len;
   1686         const char *s = luaL_checklstring(L, arg, &len);
   1687         luaL_argcheck(L, strlen(s) == len, arg, "string contains zeros");
   1688         luaL_addlstring(&b, s, len);
   1689         luaL_addchar(&b, '\0');  /* add zero at the end */
   1690         totalsize += len + 1;
   1691         break;
   1692       }
   1693       case Kpadding: luaL_addchar(&b, LUAL_PACKPADBYTE);  /* FALLTHROUGH */
   1694       case Kpaddalign: case Knop:
   1695         arg--;  /* undo increment */
   1696         break;
   1697     }
   1698   }
   1699   luaL_pushresult(&b);
   1700   return 1;
   1701 }
   1702 
   1703 
   1704 static int str_packsize (lua_State *L) {
   1705   Header h;
   1706   const char *fmt = luaL_checkstring(L, 1);  /* format string */
   1707   size_t totalsize = 0;  /* accumulate total size of result */
   1708   initheader(L, &h);
   1709   while (*fmt != '\0') {
   1710     unsigned ntoalign;
   1711     size_t size;
   1712     KOption opt = getdetails(&h, totalsize, &fmt, &size, &ntoalign);
   1713     luaL_argcheck(L, opt != Kstring && opt != Kzstr, 1,
   1714                      "variable-length format");
   1715     size += ntoalign;  /* total space used by option */
   1716     luaL_argcheck(L, totalsize <= LUA_MAXINTEGER - size,
   1717                      1, "format result too large");
   1718     totalsize += size;
   1719   }
   1720   lua_pushinteger(L, cast_st2S(totalsize));
   1721   return 1;
   1722 }
   1723 
   1724 
   1725 /*
   1726 ** Unpack an integer with 'size' bytes and 'islittle' endianness.
   1727 ** If size is smaller than the size of a Lua integer and integer
   1728 ** is signed, must do sign extension (propagating the sign to the
   1729 ** higher bits); if size is larger than the size of a Lua integer,
   1730 ** it must check the unread bytes to see whether they do not cause an
   1731 ** overflow.
   1732 */
   1733 static lua_Integer unpackint (lua_State *L, const char *str,
   1734                               int islittle, int size, int issigned) {
   1735   lua_Unsigned res = 0;
   1736   int i;
   1737   int limit = (size  <= SZINT) ? size : SZINT;
   1738   for (i = limit - 1; i >= 0; i--) {
   1739     res <<= NB;
   1740     res |= (lua_Unsigned)(unsigned char)str[islittle ? i : size - 1 - i];
   1741   }
   1742   if (size < SZINT) {  /* real size smaller than lua_Integer? */
   1743     if (issigned) {  /* needs sign extension? */
   1744       lua_Unsigned mask = (lua_Unsigned)1 << (size*NB - 1);
   1745       res = ((res ^ mask) - mask);  /* do sign extension */
   1746     }
   1747   }
   1748   else if (size > SZINT) {  /* must check unread bytes */
   1749     int mask = (!issigned || (lua_Integer)res >= 0) ? 0 : MC;
   1750     for (i = limit; i < size; i++) {
   1751       if (l_unlikely((unsigned char)str[islittle ? i : size - 1 - i] != mask))
   1752         luaL_error(L, "%d-byte integer does not fit into Lua Integer", size);
   1753     }
   1754   }
   1755   return (lua_Integer)res;
   1756 }
   1757 
   1758 
   1759 static int str_unpack (lua_State *L) {
   1760   Header h;
   1761   const char *fmt = luaL_checkstring(L, 1);
   1762   size_t ld;
   1763   const char *data = luaL_checklstring(L, 2, &ld);
   1764   size_t pos = posrelatI(luaL_optinteger(L, 3, 1), ld) - 1;
   1765   int n = 0;  /* number of results */
   1766   luaL_argcheck(L, pos <= ld, 3, "initial position out of string");
   1767   initheader(L, &h);
   1768   while (*fmt != '\0') {
   1769     unsigned ntoalign;
   1770     size_t size;
   1771     KOption opt = getdetails(&h, pos, &fmt, &size, &ntoalign);
   1772     luaL_argcheck(L, ntoalign + size <= ld - pos, 2,
   1773                     "data string too short");
   1774     pos += ntoalign;  /* skip alignment */
   1775     /* stack space for item + next position */
   1776     luaL_checkstack(L, 2, "too many results");
   1777     n++;
   1778     switch (opt) {
   1779       case Kint:
   1780       case Kuint: {
   1781         lua_Integer res = unpackint(L, data + pos, h.islittle,
   1782                                        cast_int(size), (opt == Kint));
   1783         lua_pushinteger(L, res);
   1784         break;
   1785       }
   1786       case Kfloat: {
   1787         float f;
   1788         copywithendian((char *)&f, data + pos, sizeof(f), h.islittle);
   1789         lua_pushnumber(L, (lua_Number)f);
   1790         break;
   1791       }
   1792       case Knumber: {
   1793         lua_Number f;
   1794         copywithendian((char *)&f, data + pos, sizeof(f), h.islittle);
   1795         lua_pushnumber(L, f);
   1796         break;
   1797       }
   1798       case Kdouble: {
   1799         double f;
   1800         copywithendian((char *)&f, data + pos, sizeof(f), h.islittle);
   1801         lua_pushnumber(L, (lua_Number)f);
   1802         break;
   1803       }
   1804       case Kchar: {
   1805         lua_pushlstring(L, data + pos, size);
   1806         break;
   1807       }
   1808       case Kstring: {
   1809         lua_Unsigned len = (lua_Unsigned)unpackint(L, data + pos,
   1810                                           h.islittle, cast_int(size), 0);
   1811         luaL_argcheck(L, len <= ld - pos - size, 2, "data string too short");
   1812         lua_pushlstring(L, data + pos + size, len);
   1813         pos += len;  /* skip string */
   1814         break;
   1815       }
   1816       case Kzstr: {
   1817         size_t len = strlen(data + pos);
   1818         luaL_argcheck(L, pos + len < ld, 2,
   1819                          "unfinished string for format 'z'");
   1820         lua_pushlstring(L, data + pos, len);
   1821         pos += len + 1;  /* skip string plus final '\0' */
   1822         break;
   1823       }
   1824       case Kpaddalign: case Kpadding: case Knop:
   1825         n--;  /* undo increment */
   1826         break;
   1827     }
   1828     pos += size;
   1829   }
   1830   lua_pushinteger(L, cast_st2S(pos) + 1);  /* next position */
   1831   return n + 1;
   1832 }
   1833 
   1834 /* }====================================================== */
   1835 
   1836 
   1837 static const luaL_Reg strlib[] = {
   1838   {"byte", str_byte},
   1839   {"char", str_char},
   1840   {"dump", str_dump},
   1841   {"find", str_find},
   1842   {"format", str_format},
   1843   {"gmatch", gmatch},
   1844   {"gsub", str_gsub},
   1845   {"len", str_len},
   1846   {"lower", str_lower},
   1847   {"match", str_match},
   1848   {"rep", str_rep},
   1849   {"reverse", str_reverse},
   1850   {"sub", str_sub},
   1851   {"upper", str_upper},
   1852   {"pack", str_pack},
   1853   {"packsize", str_packsize},
   1854   {"unpack", str_unpack},
   1855   {NULL, NULL}
   1856 };
   1857 
   1858 
   1859 static void createmetatable (lua_State *L) {
   1860   /* table to be metatable for strings */
   1861   luaL_newlibtable(L, stringmetamethods);
   1862   luaL_setfuncs(L, stringmetamethods, 0);
   1863   lua_pushliteral(L, "");  /* dummy string */
   1864   lua_pushvalue(L, -2);  /* copy table */
   1865   lua_setmetatable(L, -2);  /* set table as metatable for strings */
   1866   lua_pop(L, 1);  /* pop dummy string */
   1867   lua_pushvalue(L, -2);  /* get string library */
   1868   lua_setfield(L, -2, "__index");  /* metatable.__index = string */
   1869   lua_pop(L, 1);  /* pop metatable */
   1870 }
   1871 
   1872 
   1873 /*
   1874 ** Open string library
   1875 */
   1876 LUAMOD_API int luaopen_string (lua_State *L) {
   1877   luaL_newlib(L, strlib);
   1878   createmetatable(L);
   1879   return 1;
   1880 }
   1881