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lauxlib.c (35966B)


      1 /*
      2 ** $Id: lauxlib.c $
      3 ** Auxiliary functions for building Lua libraries
      4 ** See Copyright Notice in lua.h
      5 */
      6 
      7 #define lauxlib_c
      8 #define LUA_LIB
      9 
     10 #include "lprefix.h"
     11 
     12 
     13 #include <errno.h>
     14 #include <stdarg.h>
     15 #include <stdio.h>
     16 #include <stdlib.h>
     17 #include <string.h>
     18 
     19 
     20 /*
     21 ** This file uses only the official API of Lua.
     22 ** Any function declared here could be written as an application function.
     23 */
     24 
     25 #include "lua.h"
     26 
     27 #include "lauxlib.h"
     28 #include "llimits.h"
     29 
     30 
     31 /*
     32 ** {======================================================
     33 ** Traceback
     34 ** =======================================================
     35 */
     36 
     37 
     38 #define LEVELS1	10	/* size of the first part of the stack */
     39 #define LEVELS2	11	/* size of the second part of the stack */
     40 
     41 
     42 
     43 /*
     44 ** Search for 'objidx' in table at index -1. ('objidx' must be an
     45 ** absolute index.) Return 1 + string at top if it found a good name.
     46 */
     47 static int findfield (lua_State *L, int objidx, int level) {
     48   if (level == 0 || !lua_istable(L, -1))
     49     return 0;  /* not found */
     50   lua_pushnil(L);  /* start 'next' loop */
     51   while (lua_next(L, -2)) {  /* for each pair in table */
     52     if (lua_type(L, -2) == LUA_TSTRING) {  /* ignore non-string keys */
     53       if (lua_rawequal(L, objidx, -1)) {  /* found object? */
     54         lua_pop(L, 1);  /* remove value (but keep name) */
     55         return 1;
     56       }
     57       else if (findfield(L, objidx, level - 1)) {  /* try recursively */
     58         /* stack: lib_name, lib_table, field_name (top) */
     59         lua_pushliteral(L, ".");  /* place '.' between the two names */
     60         lua_replace(L, -3);  /* (in the slot occupied by table) */
     61         lua_concat(L, 3);  /* lib_name.field_name */
     62         return 1;
     63       }
     64     }
     65     lua_pop(L, 1);  /* remove value */
     66   }
     67   return 0;  /* not found */
     68 }
     69 
     70 
     71 /*
     72 ** Search for a name for a function in all loaded modules
     73 */
     74 static int pushglobalfuncname (lua_State *L, lua_Debug *ar) {
     75   int top = lua_gettop(L);
     76   lua_getinfo(L, "f", ar);  /* push function */
     77   lua_getfield(L, LUA_REGISTRYINDEX, LUA_LOADED_TABLE);
     78   luaL_checkstack(L, 6, "not enough stack");  /* slots for 'findfield' */
     79   if (findfield(L, top + 1, 2)) {
     80     const char *name = lua_tostring(L, -1);
     81     if (strncmp(name, LUA_GNAME ".", 3) == 0) {  /* name start with '_G.'? */
     82       lua_pushstring(L, name + 3);  /* push name without prefix */
     83       lua_remove(L, -2);  /* remove original name */
     84     }
     85     lua_copy(L, -1, top + 1);  /* copy name to proper place */
     86     lua_settop(L, top + 1);  /* remove table "loaded" and name copy */
     87     return 1;
     88   }
     89   else {
     90     lua_settop(L, top);  /* remove function and global table */
     91     return 0;
     92   }
     93 }
     94 
     95 
     96 static void pushfuncname (lua_State *L, lua_Debug *ar) {
     97   if (pushglobalfuncname(L, ar)) {  /* try first a global name */
     98     lua_pushfstring(L, "function '%s'", lua_tostring(L, -1));
     99     lua_remove(L, -2);  /* remove name */
    100   }
    101   else if (*ar->namewhat != '\0')  /* is there a name from code? */
    102     lua_pushfstring(L, "%s '%s'", ar->namewhat, ar->name);  /* use it */
    103   else if (*ar->what == 'm')  /* main? */
    104       lua_pushliteral(L, "main chunk");
    105   else if (*ar->what != 'C')  /* for Lua functions, use <file:line> */
    106     lua_pushfstring(L, "function <%s:%d>", ar->short_src, ar->linedefined);
    107   else  /* nothing left... */
    108     lua_pushliteral(L, "?");
    109 }
    110 
    111 
    112 static int lastlevel (lua_State *L) {
    113   lua_Debug ar;
    114   int li = 1, le = 1;
    115   /* find an upper bound */
    116   while (lua_getstack(L, le, &ar)) { li = le; le *= 2; }
    117   /* do a binary search */
    118   while (li < le) {
    119     int m = (li + le)/2;
    120     if (lua_getstack(L, m, &ar)) li = m + 1;
    121     else le = m;
    122   }
    123   return le - 1;
    124 }
    125 
    126 
    127 LUALIB_API void luaL_traceback (lua_State *L, lua_State *L1,
    128                                 const char *msg, int level) {
    129   luaL_Buffer b;
    130   lua_Debug ar;
    131   int last = lastlevel(L1);
    132   int limit2show = (last - level > LEVELS1 + LEVELS2) ? LEVELS1 : -1;
    133   luaL_buffinit(L, &b);
    134   if (msg) {
    135     luaL_addstring(&b, msg);
    136     luaL_addchar(&b, '\n');
    137   }
    138   luaL_addstring(&b, "stack traceback:");
    139   while (lua_getstack(L1, level++, &ar)) {
    140     if (limit2show-- == 0) {  /* too many levels? */
    141       int n = last - level - LEVELS2 + 1;  /* number of levels to skip */
    142       lua_pushfstring(L, "\n\t...\t(skipping %d levels)", n);
    143       luaL_addvalue(&b);  /* add warning about skip */
    144       level += n;  /* and skip to last levels */
    145     }
    146     else {
    147       lua_getinfo(L1, "Slnt", &ar);
    148       if (ar.currentline <= 0)
    149         lua_pushfstring(L, "\n\t%s: in ", ar.short_src);
    150       else
    151         lua_pushfstring(L, "\n\t%s:%d: in ", ar.short_src, ar.currentline);
    152       luaL_addvalue(&b);
    153       pushfuncname(L, &ar);
    154       luaL_addvalue(&b);
    155       if (ar.istailcall)
    156         luaL_addstring(&b, "\n\t(...tail calls...)");
    157     }
    158   }
    159   luaL_pushresult(&b);
    160 }
    161 
    162 /* }====================================================== */
    163 
    164 
    165 /*
    166 ** {======================================================
    167 ** Error-report functions
    168 ** =======================================================
    169 */
    170 
    171 LUALIB_API int luaL_argerror (lua_State *L, int arg, const char *extramsg) {
    172   lua_Debug ar;
    173   const char *argword;
    174   if (!lua_getstack(L, 0, &ar))  /* no stack frame? */
    175     return luaL_error(L, "bad argument #%d (%s)", arg, extramsg);
    176   lua_getinfo(L, "nt", &ar);
    177   if (arg <= ar.extraargs)  /* error in an extra argument? */
    178     argword =  "extra argument";
    179   else {
    180     arg -= ar.extraargs;  /* do not count extra arguments */
    181     if (strcmp(ar.namewhat, "method") == 0) {  /* colon syntax? */
    182       arg--;  /* do not count (extra) self argument */
    183       if (arg == 0)  /* error in self argument? */
    184         return luaL_error(L, "calling '%s' on bad self (%s)",
    185                                ar.name, extramsg);
    186       /* else go through; error in a regular argument */
    187     }
    188     argword = "argument";
    189   }
    190   if (ar.name == NULL)
    191     ar.name = (pushglobalfuncname(L, &ar)) ? lua_tostring(L, -1) : "?";
    192   return luaL_error(L, "bad %s #%d to '%s' (%s)",
    193                        argword, arg, ar.name, extramsg);
    194 }
    195 
    196 
    197 LUALIB_API int luaL_typeerror (lua_State *L, int arg, const char *tname) {
    198   const char *msg;
    199   const char *typearg;  /* name for the type of the actual argument */
    200   if (luaL_getmetafield(L, arg, "__name") == LUA_TSTRING)
    201     typearg = lua_tostring(L, -1);  /* use the given type name */
    202   else if (lua_type(L, arg) == LUA_TLIGHTUSERDATA)
    203     typearg = "light userdata";  /* special name for messages */
    204   else
    205     typearg = luaL_typename(L, arg);  /* standard name */
    206   msg = lua_pushfstring(L, "%s expected, got %s", tname, typearg);
    207   return luaL_argerror(L, arg, msg);
    208 }
    209 
    210 
    211 static void tag_error (lua_State *L, int arg, int tag) {
    212   luaL_typeerror(L, arg, lua_typename(L, tag));
    213 }
    214 
    215 
    216 /*
    217 ** The use of 'lua_pushfstring' ensures this function does not
    218 ** need reserved stack space when called.
    219 */
    220 LUALIB_API void luaL_where (lua_State *L, int level) {
    221   lua_Debug ar;
    222   if (lua_getstack(L, level, &ar)) {  /* check function at level */
    223     lua_getinfo(L, "Sl", &ar);  /* get info about it */
    224     if (ar.currentline > 0) {  /* is there info? */
    225       lua_pushfstring(L, "%s:%d: ", ar.short_src, ar.currentline);
    226       return;
    227     }
    228   }
    229   lua_pushfstring(L, "");  /* else, no information available... */
    230 }
    231 
    232 
    233 /*
    234 ** Again, the use of 'lua_pushvfstring' ensures this function does
    235 ** not need reserved stack space when called. (At worst, it generates
    236 ** a memory error instead of the given message.)
    237 */
    238 LUALIB_API int luaL_error (lua_State *L, const char *fmt, ...) {
    239   va_list argp;
    240   va_start(argp, fmt);
    241   luaL_where(L, 1);
    242   lua_pushvfstring(L, fmt, argp);
    243   va_end(argp);
    244   lua_concat(L, 2);
    245   return lua_error(L);
    246 }
    247 
    248 
    249 LUALIB_API int luaL_fileresult (lua_State *L, int stat, const char *fname) {
    250   int en = errno;  /* calls to Lua API may change this value */
    251   if (stat) {
    252     lua_pushboolean(L, 1);
    253     return 1;
    254   }
    255   else {
    256     const char *msg;
    257     luaL_pushfail(L);
    258     msg = (en != 0) ? strerror(en) : "(no extra info)";
    259     if (fname)
    260       lua_pushfstring(L, "%s: %s", fname, msg);
    261     else
    262       lua_pushstring(L, msg);
    263     lua_pushinteger(L, en);
    264     return 3;
    265   }
    266 }
    267 
    268 
    269 #if !defined(l_inspectstat)	/* { */
    270 
    271 #if defined(LUA_USE_POSIX)
    272 
    273 #include <sys/wait.h>
    274 
    275 /*
    276 ** use appropriate macros to interpret 'pclose' return status
    277 */
    278 #define l_inspectstat(stat,what)  \
    279    if (WIFEXITED(stat)) { stat = WEXITSTATUS(stat); } \
    280    else if (WIFSIGNALED(stat)) { stat = WTERMSIG(stat); what = "signal"; }
    281 
    282 #else
    283 
    284 #define l_inspectstat(stat,what)  /* no op */
    285 
    286 #endif
    287 
    288 #endif				/* } */
    289 
    290 
    291 LUALIB_API int luaL_execresult (lua_State *L, int stat) {
    292   if (stat != 0 && errno != 0)  /* error with an 'errno'? */
    293     return luaL_fileresult(L, 0, NULL);
    294   else {
    295     const char *what = "exit";  /* type of termination */
    296     l_inspectstat(stat, what);  /* interpret result */
    297     if (*what == 'e' && stat == 0)  /* successful termination? */
    298       lua_pushboolean(L, 1);
    299     else
    300       luaL_pushfail(L);
    301     lua_pushstring(L, what);
    302     lua_pushinteger(L, stat);
    303     return 3;  /* return true/fail,what,code */
    304   }
    305 }
    306 
    307 /* }====================================================== */
    308 
    309 
    310 
    311 /*
    312 ** {======================================================
    313 ** Userdata's metatable manipulation
    314 ** =======================================================
    315 */
    316 
    317 LUALIB_API int luaL_newmetatable (lua_State *L, const char *tname) {
    318   if (luaL_getmetatable(L, tname) != LUA_TNIL)  /* name already in use? */
    319     return 0;  /* leave previous value on top, but return 0 */
    320   lua_pop(L, 1);
    321   lua_createtable(L, 0, 2);  /* create metatable */
    322   lua_pushstring(L, tname);
    323   lua_setfield(L, -2, "__name");  /* metatable.__name = tname */
    324   lua_pushvalue(L, -1);
    325   lua_setfield(L, LUA_REGISTRYINDEX, tname);  /* registry.name = metatable */
    326   return 1;
    327 }
    328 
    329 
    330 LUALIB_API void luaL_setmetatable (lua_State *L, const char *tname) {
    331   luaL_getmetatable(L, tname);
    332   lua_setmetatable(L, -2);
    333 }
    334 
    335 
    336 LUALIB_API void *luaL_testudata (lua_State *L, int ud, const char *tname) {
    337   void *p = lua_touserdata(L, ud);
    338   if (p != NULL) {  /* value is a userdata? */
    339     if (lua_getmetatable(L, ud)) {  /* does it have a metatable? */
    340       luaL_getmetatable(L, tname);  /* get correct metatable */
    341       if (!lua_rawequal(L, -1, -2))  /* not the same? */
    342         p = NULL;  /* value is a userdata with wrong metatable */
    343       lua_pop(L, 2);  /* remove both metatables */
    344       return p;
    345     }
    346   }
    347   return NULL;  /* value is not a userdata with a metatable */
    348 }
    349 
    350 
    351 LUALIB_API void *luaL_checkudata (lua_State *L, int ud, const char *tname) {
    352   void *p = luaL_testudata(L, ud, tname);
    353   luaL_argexpected(L, p != NULL, ud, tname);
    354   return p;
    355 }
    356 
    357 /* }====================================================== */
    358 
    359 
    360 /*
    361 ** {======================================================
    362 ** Argument check functions
    363 ** =======================================================
    364 */
    365 
    366 LUALIB_API int luaL_checkoption (lua_State *L, int arg, const char *def,
    367                                  const char *const lst[]) {
    368   const char *name = (def) ? luaL_optstring(L, arg, def) :
    369                              luaL_checkstring(L, arg);
    370   int i;
    371   for (i=0; lst[i]; i++)
    372     if (strcmp(lst[i], name) == 0)
    373       return i;
    374   return luaL_argerror(L, arg,
    375                        lua_pushfstring(L, "invalid option '%s'", name));
    376 }
    377 
    378 
    379 /*
    380 ** Ensures the stack has at least 'space' extra slots, raising an error
    381 ** if it cannot fulfill the request. (The error handling needs a few
    382 ** extra slots to format the error message. In case of an error without
    383 ** this extra space, Lua will generate the same 'stack overflow' error,
    384 ** but without 'msg'.)
    385 */
    386 LUALIB_API void luaL_checkstack (lua_State *L, int space, const char *msg) {
    387   if (l_unlikely(!lua_checkstack(L, space))) {
    388     if (msg)
    389       luaL_error(L, "stack overflow (%s)", msg);
    390     else
    391       luaL_error(L, "stack overflow");
    392   }
    393 }
    394 
    395 
    396 LUALIB_API void luaL_checktype (lua_State *L, int arg, int t) {
    397   if (l_unlikely(lua_type(L, arg) != t))
    398     tag_error(L, arg, t);
    399 }
    400 
    401 
    402 LUALIB_API void luaL_checkany (lua_State *L, int arg) {
    403   if (l_unlikely(lua_type(L, arg) == LUA_TNONE))
    404     luaL_argerror(L, arg, "value expected");
    405 }
    406 
    407 
    408 LUALIB_API const char *luaL_checklstring (lua_State *L, int arg, size_t *len) {
    409   const char *s = lua_tolstring(L, arg, len);
    410   if (l_unlikely(!s)) tag_error(L, arg, LUA_TSTRING);
    411   return s;
    412 }
    413 
    414 
    415 LUALIB_API const char *luaL_optlstring (lua_State *L, int arg,
    416                                         const char *def, size_t *len) {
    417   if (lua_isnoneornil(L, arg)) {
    418     if (len)
    419       *len = (def ? strlen(def) : 0);
    420     return def;
    421   }
    422   else return luaL_checklstring(L, arg, len);
    423 }
    424 
    425 
    426 LUALIB_API lua_Number luaL_checknumber (lua_State *L, int arg) {
    427   int isnum;
    428   lua_Number d = lua_tonumberx(L, arg, &isnum);
    429   if (l_unlikely(!isnum))
    430     tag_error(L, arg, LUA_TNUMBER);
    431   return d;
    432 }
    433 
    434 
    435 LUALIB_API lua_Number luaL_optnumber (lua_State *L, int arg, lua_Number def) {
    436   return luaL_opt(L, luaL_checknumber, arg, def);
    437 }
    438 
    439 
    440 static void interror (lua_State *L, int arg) {
    441   if (lua_isnumber(L, arg))
    442     luaL_argerror(L, arg, "number has no integer representation");
    443   else
    444     tag_error(L, arg, LUA_TNUMBER);
    445 }
    446 
    447 
    448 LUALIB_API lua_Integer luaL_checkinteger (lua_State *L, int arg) {
    449   int isnum;
    450   lua_Integer d = lua_tointegerx(L, arg, &isnum);
    451   if (l_unlikely(!isnum)) {
    452     interror(L, arg);
    453   }
    454   return d;
    455 }
    456 
    457 
    458 LUALIB_API lua_Integer luaL_optinteger (lua_State *L, int arg,
    459                                                       lua_Integer def) {
    460   return luaL_opt(L, luaL_checkinteger, arg, def);
    461 }
    462 
    463 /* }====================================================== */
    464 
    465 
    466 /*
    467 ** {======================================================
    468 ** Generic Buffer manipulation
    469 ** =======================================================
    470 */
    471 
    472 /* userdata to box arbitrary data */
    473 typedef struct UBox {
    474   void *box;
    475   size_t bsize;
    476 } UBox;
    477 
    478 
    479 /* Resize the buffer used by a box. Optimize for the common case of
    480 ** resizing to the old size. (For instance, __gc will resize the box
    481 ** to 0 even after it was closed. 'pushresult' may also resize it to a
    482 ** final size that is equal to the one set when the buffer was created.)
    483 */
    484 static void *resizebox (lua_State *L, int idx, size_t newsize) {
    485   UBox *box = (UBox *)lua_touserdata(L, idx);
    486   if (box->bsize == newsize)  /* not changing size? */
    487     return box->box;  /* keep the buffer */
    488   else {
    489     void *ud;
    490     lua_Alloc allocf = lua_getallocf(L, &ud);
    491     void *temp = allocf(ud, box->box, box->bsize, newsize);
    492     if (l_unlikely(temp == NULL && newsize > 0)) {  /* allocation error? */
    493       lua_pushliteral(L, "not enough memory");
    494       lua_error(L);  /* raise a memory error */
    495     }
    496     box->box = temp;
    497     box->bsize = newsize;
    498     return temp;
    499   }
    500 }
    501 
    502 
    503 static int boxgc (lua_State *L) {
    504   resizebox(L, 1, 0);
    505   return 0;
    506 }
    507 
    508 
    509 static const luaL_Reg boxmt[] = {  /* box metamethods */
    510   {"__gc", boxgc},
    511   {"__close", boxgc},
    512   {NULL, NULL}
    513 };
    514 
    515 
    516 static void newbox (lua_State *L) {
    517   UBox *box = (UBox *)lua_newuserdatauv(L, sizeof(UBox), 0);
    518   box->box = NULL;
    519   box->bsize = 0;
    520   if (luaL_newmetatable(L, "_UBOX*"))  /* creating metatable? */
    521     luaL_setfuncs(L, boxmt, 0);  /* set its metamethods */
    522   lua_setmetatable(L, -2);
    523 }
    524 
    525 
    526 /*
    527 ** check whether buffer is using a userdata on the stack as a temporary
    528 ** buffer
    529 */
    530 #define buffonstack(B)	((B)->b != (B)->init.b)
    531 
    532 
    533 /*
    534 ** Whenever buffer is accessed, slot 'idx' must either be a box (which
    535 ** cannot be NULL) or it is a placeholder for the buffer.
    536 */
    537 #define checkbufferlevel(B,idx)  \
    538   lua_assert(buffonstack(B) ? lua_touserdata(B->L, idx) != NULL  \
    539                             : lua_touserdata(B->L, idx) == (void*)B)
    540 
    541 
    542 /*
    543 ** Compute new size for buffer 'B', enough to accommodate extra 'sz'
    544 ** bytes plus one for a terminating zero. (The test for "not big enough"
    545 ** also gets the case when the computation of 'newsize' overflows.)
    546 */
    547 static size_t newbuffsize (luaL_Buffer *B, size_t sz) {
    548   size_t newsize = (B->size / 2) * 3;  /* buffer size * 1.5 */
    549   if (l_unlikely(sz > MAX_SIZE - B->n - 1))
    550     return cast_sizet(luaL_error(B->L, "resulting string too large"));
    551   if (newsize < B->n + sz + 1 || newsize > MAX_SIZE) {
    552     /* newsize was not big enough or too big */
    553     newsize = B->n + sz + 1;
    554   }
    555   return newsize;
    556 }
    557 
    558 
    559 /*
    560 ** Returns a pointer to a free area with at least 'sz' bytes in buffer
    561 ** 'B'. 'boxidx' is the relative position in the stack where is the
    562 ** buffer's box or its placeholder.
    563 */
    564 static char *prepbuffsize (luaL_Buffer *B, size_t sz, int boxidx) {
    565   checkbufferlevel(B, boxidx);
    566   if (B->size - B->n >= sz)  /* enough space? */
    567     return B->b + B->n;
    568   else {
    569     lua_State *L = B->L;
    570     char *newbuff;
    571     size_t newsize = newbuffsize(B, sz);
    572     /* create larger buffer */
    573     if (buffonstack(B))  /* buffer already has a box? */
    574       newbuff = (char *)resizebox(L, boxidx, newsize);  /* resize it */
    575     else {  /* no box yet */
    576       lua_remove(L, boxidx);  /* remove placeholder */
    577       newbox(L);  /* create a new box */
    578       lua_insert(L, boxidx);  /* move box to its intended position */
    579       lua_toclose(L, boxidx);
    580       newbuff = (char *)resizebox(L, boxidx, newsize);
    581       memcpy(newbuff, B->b, B->n * sizeof(char));  /* copy original content */
    582     }
    583     B->b = newbuff;
    584     B->size = newsize;
    585     return newbuff + B->n;
    586   }
    587 }
    588 
    589 /*
    590 ** returns a pointer to a free area with at least 'sz' bytes
    591 */
    592 LUALIB_API char *luaL_prepbuffsize (luaL_Buffer *B, size_t sz) {
    593   return prepbuffsize(B, sz, -1);
    594 }
    595 
    596 
    597 LUALIB_API void luaL_addlstring (luaL_Buffer *B, const char *s, size_t l) {
    598   if (l > 0) {  /* avoid 'memcpy' when 's' can be NULL */
    599     char *b = prepbuffsize(B, l, -1);
    600     memcpy(b, s, l * sizeof(char));
    601     luaL_addsize(B, l);
    602   }
    603 }
    604 
    605 
    606 LUALIB_API void luaL_addstring (luaL_Buffer *B, const char *s) {
    607   luaL_addlstring(B, s, strlen(s));
    608 }
    609 
    610 
    611 LUALIB_API void luaL_pushresult (luaL_Buffer *B) {
    612   lua_State *L = B->L;
    613   checkbufferlevel(B, -1);
    614   if (!buffonstack(B))  /* using static buffer? */
    615     lua_pushlstring(L, B->b, B->n);  /* save result as regular string */
    616   else {  /* reuse buffer already allocated */
    617     UBox *box = (UBox *)lua_touserdata(L, -1);
    618     void *ud;
    619     lua_Alloc allocf = lua_getallocf(L, &ud);  /* function to free buffer */
    620     size_t len = B->n;  /* final string length */
    621     char *s;
    622     resizebox(L, -1, len + 1);  /* adjust box size to content size */
    623     s = (char*)box->box;  /* final buffer address */
    624     s[len] = '\0';  /* add ending zero */
    625     /* clear box, as Lua will take control of the buffer */
    626     box->bsize = 0;  box->box = NULL;
    627     lua_pushexternalstring(L, s, len, allocf, ud);
    628     lua_closeslot(L, -2);  /* close the box */
    629     lua_gc(L, LUA_GCSTEP, len);
    630   }
    631   lua_remove(L, -2);  /* remove box or placeholder from the stack */
    632 }
    633 
    634 
    635 LUALIB_API void luaL_pushresultsize (luaL_Buffer *B, size_t sz) {
    636   luaL_addsize(B, sz);
    637   luaL_pushresult(B);
    638 }
    639 
    640 
    641 /*
    642 ** 'luaL_addvalue' is the only function in the Buffer system where the
    643 ** box (if existent) is not on the top of the stack. So, instead of
    644 ** calling 'luaL_addlstring', it replicates the code using -2 as the
    645 ** last argument to 'prepbuffsize', signaling that the box is (or will
    646 ** be) below the string being added to the buffer. (Box creation can
    647 ** trigger an emergency GC, so we should not remove the string from the
    648 ** stack before we have the space guaranteed.)
    649 */
    650 LUALIB_API void luaL_addvalue (luaL_Buffer *B) {
    651   lua_State *L = B->L;
    652   size_t len;
    653   const char *s = lua_tolstring(L, -1, &len);
    654   char *b = prepbuffsize(B, len, -2);
    655   memcpy(b, s, len * sizeof(char));
    656   luaL_addsize(B, len);
    657   lua_pop(L, 1);  /* pop string */
    658 }
    659 
    660 
    661 LUALIB_API void luaL_buffinit (lua_State *L, luaL_Buffer *B) {
    662   B->L = L;
    663   B->b = B->init.b;
    664   B->n = 0;
    665   B->size = LUAL_BUFFERSIZE;
    666   lua_pushlightuserdata(L, (void*)B);  /* push placeholder */
    667 }
    668 
    669 
    670 LUALIB_API char *luaL_buffinitsize (lua_State *L, luaL_Buffer *B, size_t sz) {
    671   luaL_buffinit(L, B);
    672   return prepbuffsize(B, sz, -1);
    673 }
    674 
    675 /* }====================================================== */
    676 
    677 
    678 /*
    679 ** {======================================================
    680 ** Reference system
    681 ** =======================================================
    682 */
    683 
    684 /*
    685 ** The previously freed references form a linked list: t[1] is the index
    686 ** of a first free index, t[t[1]] is the index of the second element,
    687 ** etc. A zero signals the end of the list.
    688 */
    689 LUALIB_API int luaL_ref (lua_State *L, int t) {
    690   int ref;
    691   if (lua_isnil(L, -1)) {
    692     lua_pop(L, 1);  /* remove from stack */
    693     return LUA_REFNIL;  /* 'nil' has a unique fixed reference */
    694   }
    695   t = lua_absindex(L, t);
    696   if (lua_rawgeti(L, t, 1) == LUA_TNUMBER)  /* already initialized? */
    697     ref = (int)lua_tointeger(L, -1);  /* ref = t[1] */
    698   else {  /* first access */
    699     lua_assert(!lua_toboolean(L, -1));  /* must be nil or false */
    700     ref = 0;  /* list is empty */
    701     lua_pushinteger(L, 0);  /* initialize as an empty list */
    702     lua_rawseti(L, t, 1);  /* ref = t[1] = 0 */
    703   }
    704   lua_pop(L, 1);  /* remove element from stack */
    705   if (ref != 0) {  /* any free element? */
    706     lua_rawgeti(L, t, ref);  /* remove it from list */
    707     lua_rawseti(L, t, 1);  /* (t[1] = t[ref]) */
    708   }
    709   else  /* no free elements */
    710     ref = (int)lua_rawlen(L, t) + 1;  /* get a new reference */
    711   lua_rawseti(L, t, ref);
    712   return ref;
    713 }
    714 
    715 
    716 LUALIB_API void luaL_unref (lua_State *L, int t, int ref) {
    717   if (ref >= 0) {
    718     t = lua_absindex(L, t);
    719     lua_rawgeti(L, t, 1);
    720     lua_assert(lua_isinteger(L, -1));
    721     lua_rawseti(L, t, ref);  /* t[ref] = t[1] */
    722     lua_pushinteger(L, ref);
    723     lua_rawseti(L, t, 1);  /* t[1] = ref */
    724   }
    725 }
    726 
    727 /* }====================================================== */
    728 
    729 
    730 /*
    731 ** {======================================================
    732 ** Load functions
    733 ** =======================================================
    734 */
    735 
    736 typedef struct LoadF {
    737   unsigned n;  /* number of pre-read characters */
    738   FILE *f;  /* file being read */
    739   char buff[BUFSIZ];  /* area for reading file */
    740 } LoadF;
    741 
    742 
    743 static const char *getF (lua_State *L, void *ud, size_t *size) {
    744   LoadF *lf = (LoadF *)ud;
    745   (void)L;  /* not used */
    746   if (lf->n > 0) {  /* are there pre-read characters to be read? */
    747     *size = lf->n;  /* return them (chars already in buffer) */
    748     lf->n = 0;  /* no more pre-read characters */
    749   }
    750   else {  /* read a block from file */
    751     /* 'fread' can return > 0 *and* set the EOF flag. If next call to
    752        'getF' called 'fread', it might still wait for user input.
    753        The next check avoids this problem. */
    754     if (feof(lf->f)) return NULL;
    755     *size = fread(lf->buff, 1, sizeof(lf->buff), lf->f);  /* read block */
    756   }
    757   return lf->buff;
    758 }
    759 
    760 
    761 static int errfile (lua_State *L, const char *what, int fnameindex) {
    762   int err = errno;
    763   const char *filename = lua_tostring(L, fnameindex) + 1;
    764   if (err != 0)
    765     lua_pushfstring(L, "cannot %s %s: %s", what, filename, strerror(err));
    766   else
    767     lua_pushfstring(L, "cannot %s %s", what, filename);
    768   lua_remove(L, fnameindex);
    769   return LUA_ERRFILE;
    770 }
    771 
    772 
    773 /*
    774 ** Skip an optional BOM at the start of a stream. If there is an
    775 ** incomplete BOM (the first character is correct but the rest is
    776 ** not), returns the first character anyway to force an error
    777 ** (as no chunk can start with 0xEF).
    778 */
    779 static int skipBOM (FILE *f) {
    780   int c = getc(f);  /* read first character */
    781   if (c == 0xEF && getc(f) == 0xBB && getc(f) == 0xBF)  /* correct BOM? */
    782     return getc(f);  /* ignore BOM and return next char */
    783   else  /* no (valid) BOM */
    784     return c;  /* return first character */
    785 }
    786 
    787 
    788 /*
    789 ** reads the first character of file 'f' and skips an optional BOM mark
    790 ** in its beginning plus its first line if it starts with '#'. Returns
    791 ** true if it skipped the first line.  In any case, '*cp' has the
    792 ** first "valid" character of the file (after the optional BOM and
    793 ** a first-line comment).
    794 */
    795 static int skipcomment (FILE *f, int *cp) {
    796   int c = *cp = skipBOM(f);
    797   if (c == '#') {  /* first line is a comment (Unix exec. file)? */
    798     do {  /* skip first line */
    799       c = getc(f);
    800     } while (c != EOF && c != '\n');
    801     *cp = getc(f);  /* next character after comment, if present */
    802     return 1;  /* there was a comment */
    803   }
    804   else return 0;  /* no comment */
    805 }
    806 
    807 
    808 LUALIB_API int luaL_loadfilex (lua_State *L, const char *filename,
    809                                              const char *mode) {
    810   LoadF lf;
    811   int status, readstatus;
    812   int c;
    813   int fnameindex = lua_gettop(L) + 1;  /* index of filename on the stack */
    814   if (filename == NULL) {
    815     lua_pushliteral(L, "=stdin");
    816     lf.f = stdin;
    817   }
    818   else {
    819     lua_pushfstring(L, "@%s", filename);
    820     errno = 0;
    821     lf.f = fopen(filename, "r");
    822     if (lf.f == NULL) return errfile(L, "open", fnameindex);
    823   }
    824   lf.n = 0;
    825   if (skipcomment(lf.f, &c))  /* read initial portion */
    826     lf.buff[lf.n++] = '\n';  /* add newline to correct line numbers */
    827   if (c == LUA_SIGNATURE[0]) {  /* binary file? */
    828     lf.n = 0;  /* remove possible newline */
    829     if (filename) {  /* "real" file? */
    830       errno = 0;
    831       lf.f = freopen(filename, "rb", lf.f);  /* reopen in binary mode */
    832       if (lf.f == NULL) return errfile(L, "reopen", fnameindex);
    833       skipcomment(lf.f, &c);  /* re-read initial portion */
    834     }
    835   }
    836   if (c != EOF)
    837     lf.buff[lf.n++] = cast_char(c);  /* 'c' is the first character */
    838   status = lua_load(L, getF, &lf, lua_tostring(L, -1), mode);
    839   readstatus = ferror(lf.f);
    840   errno = 0;  /* no useful error number until here */
    841   if (filename) fclose(lf.f);  /* close file (even in case of errors) */
    842   if (readstatus) {
    843     lua_settop(L, fnameindex);  /* ignore results from 'lua_load' */
    844     return errfile(L, "read", fnameindex);
    845   }
    846   lua_remove(L, fnameindex);
    847   return status;
    848 }
    849 
    850 
    851 typedef struct LoadS {
    852   const char *s;
    853   size_t size;
    854 } LoadS;
    855 
    856 
    857 static const char *getS (lua_State *L, void *ud, size_t *size) {
    858   LoadS *ls = (LoadS *)ud;
    859   (void)L;  /* not used */
    860   if (ls->size == 0) return NULL;
    861   *size = ls->size;
    862   ls->size = 0;
    863   return ls->s;
    864 }
    865 
    866 
    867 LUALIB_API int luaL_loadbufferx (lua_State *L, const char *buff, size_t size,
    868                                  const char *name, const char *mode) {
    869   LoadS ls;
    870   ls.s = buff;
    871   ls.size = size;
    872   return lua_load(L, getS, &ls, name, mode);
    873 }
    874 
    875 
    876 LUALIB_API int luaL_loadstring (lua_State *L, const char *s) {
    877   return luaL_loadbuffer(L, s, strlen(s), s);
    878 }
    879 
    880 /* }====================================================== */
    881 
    882 
    883 
    884 LUALIB_API int luaL_getmetafield (lua_State *L, int obj, const char *event) {
    885   if (!lua_getmetatable(L, obj))  /* no metatable? */
    886     return LUA_TNIL;
    887   else {
    888     int tt;
    889     lua_pushstring(L, event);
    890     tt = lua_rawget(L, -2);
    891     if (tt == LUA_TNIL)  /* is metafield nil? */
    892       lua_pop(L, 2);  /* remove metatable and metafield */
    893     else
    894       lua_remove(L, -2);  /* remove only metatable */
    895     return tt;  /* return metafield type */
    896   }
    897 }
    898 
    899 
    900 LUALIB_API int luaL_callmeta (lua_State *L, int obj, const char *event) {
    901   obj = lua_absindex(L, obj);
    902   if (luaL_getmetafield(L, obj, event) == LUA_TNIL)  /* no metafield? */
    903     return 0;
    904   lua_pushvalue(L, obj);
    905   lua_call(L, 1, 1);
    906   return 1;
    907 }
    908 
    909 
    910 LUALIB_API lua_Integer luaL_len (lua_State *L, int idx) {
    911   lua_Integer l;
    912   int isnum;
    913   lua_len(L, idx);
    914   l = lua_tointegerx(L, -1, &isnum);
    915   if (l_unlikely(!isnum))
    916     luaL_error(L, "object length is not an integer");
    917   lua_pop(L, 1);  /* remove object */
    918   return l;
    919 }
    920 
    921 
    922 LUALIB_API const char *luaL_tolstring (lua_State *L, int idx, size_t *len) {
    923   idx = lua_absindex(L,idx);
    924   if (luaL_callmeta(L, idx, "__tostring")) {  /* metafield? */
    925     if (!lua_isstring(L, -1))
    926       luaL_error(L, "'__tostring' must return a string");
    927   }
    928   else {
    929     switch (lua_type(L, idx)) {
    930       case LUA_TNUMBER: {
    931         char buff[LUA_N2SBUFFSZ];
    932         lua_numbertocstring(L, idx, buff);
    933         lua_pushstring(L, buff);
    934         break;
    935       }
    936       case LUA_TSTRING:
    937         lua_pushvalue(L, idx);
    938         break;
    939       case LUA_TBOOLEAN:
    940         lua_pushstring(L, (lua_toboolean(L, idx) ? "true" : "false"));
    941         break;
    942       case LUA_TNIL:
    943         lua_pushliteral(L, "nil");
    944         break;
    945       default: {
    946         int tt = luaL_getmetafield(L, idx, "__name");  /* try name */
    947         const char *kind = (tt == LUA_TSTRING) ? lua_tostring(L, -1) :
    948                                                  luaL_typename(L, idx);
    949         lua_pushfstring(L, "%s: %p", kind, lua_topointer(L, idx));
    950         if (tt != LUA_TNIL)
    951           lua_remove(L, -2);  /* remove '__name' */
    952         break;
    953       }
    954     }
    955   }
    956   return lua_tolstring(L, -1, len);
    957 }
    958 
    959 
    960 /*
    961 ** set functions from list 'l' into table at top - 'nup'; each
    962 ** function gets the 'nup' elements at the top as upvalues.
    963 ** Returns with only the table at the stack.
    964 */
    965 LUALIB_API void luaL_setfuncs (lua_State *L, const luaL_Reg *l, int nup) {
    966   luaL_checkstack(L, nup, "too many upvalues");
    967   for (; l->name != NULL; l++) {  /* fill the table with given functions */
    968     if (l->func == NULL)  /* placeholder? */
    969       lua_pushboolean(L, 0);
    970     else {
    971       int i;
    972       for (i = 0; i < nup; i++)  /* copy upvalues to the top */
    973         lua_pushvalue(L, -nup);
    974       lua_pushcclosure(L, l->func, nup);  /* closure with those upvalues */
    975     }
    976     lua_setfield(L, -(nup + 2), l->name);
    977   }
    978   lua_pop(L, nup);  /* remove upvalues */
    979 }
    980 
    981 
    982 /*
    983 ** ensure that stack[idx][fname] has a table and push that table
    984 ** into the stack
    985 */
    986 LUALIB_API int luaL_getsubtable (lua_State *L, int idx, const char *fname) {
    987   if (lua_getfield(L, idx, fname) == LUA_TTABLE)
    988     return 1;  /* table already there */
    989   else {
    990     lua_pop(L, 1);  /* remove previous result */
    991     idx = lua_absindex(L, idx);
    992     lua_newtable(L);
    993     lua_pushvalue(L, -1);  /* copy to be left at top */
    994     lua_setfield(L, idx, fname);  /* assign new table to field */
    995     return 0;  /* false, because did not find table there */
    996   }
    997 }
    998 
    999 
   1000 /*
   1001 ** Stripped-down 'require': After checking "loaded" table, calls 'openf'
   1002 ** to open a module, registers the result in 'package.loaded' table and,
   1003 ** if 'glb' is true, also registers the result in the global table.
   1004 ** Leaves resulting module on the top.
   1005 */
   1006 LUALIB_API void luaL_requiref (lua_State *L, const char *modname,
   1007                                lua_CFunction openf, int glb) {
   1008   luaL_getsubtable(L, LUA_REGISTRYINDEX, LUA_LOADED_TABLE);
   1009   lua_getfield(L, -1, modname);  /* LOADED[modname] */
   1010   if (!lua_toboolean(L, -1)) {  /* package not already loaded? */
   1011     lua_pop(L, 1);  /* remove field */
   1012     lua_pushcfunction(L, openf);
   1013     lua_pushstring(L, modname);  /* argument to open function */
   1014     lua_call(L, 1, 1);  /* call 'openf' to open module */
   1015     lua_pushvalue(L, -1);  /* make copy of module (call result) */
   1016     lua_setfield(L, -3, modname);  /* LOADED[modname] = module */
   1017   }
   1018   lua_remove(L, -2);  /* remove LOADED table */
   1019   if (glb) {
   1020     lua_pushvalue(L, -1);  /* copy of module */
   1021     lua_setglobal(L, modname);  /* _G[modname] = module */
   1022   }
   1023 }
   1024 
   1025 
   1026 LUALIB_API void luaL_addgsub (luaL_Buffer *b, const char *s,
   1027                                      const char *p, const char *r) {
   1028   const char *wild;
   1029   size_t l = strlen(p);
   1030   while ((wild = strstr(s, p)) != NULL) {
   1031     luaL_addlstring(b, s, ct_diff2sz(wild - s));  /* push prefix */
   1032     luaL_addstring(b, r);  /* push replacement in place of pattern */
   1033     s = wild + l;  /* continue after 'p' */
   1034   }
   1035   luaL_addstring(b, s);  /* push last suffix */
   1036 }
   1037 
   1038 
   1039 LUALIB_API const char *luaL_gsub (lua_State *L, const char *s,
   1040                                   const char *p, const char *r) {
   1041   luaL_Buffer b;
   1042   luaL_buffinit(L, &b);
   1043   luaL_addgsub(&b, s, p, r);
   1044   luaL_pushresult(&b);
   1045   return lua_tostring(L, -1);
   1046 }
   1047 
   1048 
   1049 static void *l_alloc (void *ud, void *ptr, size_t osize, size_t nsize) {
   1050   (void)ud; (void)osize;  /* not used */
   1051   if (nsize == 0) {
   1052     free(ptr);
   1053     return NULL;
   1054   }
   1055   else
   1056     return realloc(ptr, nsize);
   1057 }
   1058 
   1059 
   1060 /*
   1061 ** Standard panic function just prints an error message. The test
   1062 ** with 'lua_type' avoids possible memory errors in 'lua_tostring'.
   1063 */
   1064 static int panic (lua_State *L) {
   1065   const char *msg = (lua_type(L, -1) == LUA_TSTRING)
   1066                   ? lua_tostring(L, -1)
   1067                   : "error object is not a string";
   1068   lua_writestringerror("PANIC: unprotected error in call to Lua API (%s)\n",
   1069                         msg);
   1070   return 0;  /* return to Lua to abort */
   1071 }
   1072 
   1073 
   1074 /*
   1075 ** Warning functions:
   1076 ** warnfoff: warning system is off
   1077 ** warnfon: ready to start a new message
   1078 ** warnfcont: previous message is to be continued
   1079 */
   1080 static void warnfoff (void *ud, const char *message, int tocont);
   1081 static void warnfon (void *ud, const char *message, int tocont);
   1082 static void warnfcont (void *ud, const char *message, int tocont);
   1083 
   1084 
   1085 /*
   1086 ** Check whether message is a control message. If so, execute the
   1087 ** control or ignore it if unknown.
   1088 */
   1089 static int checkcontrol (lua_State *L, const char *message, int tocont) {
   1090   if (tocont || *(message++) != '@')  /* not a control message? */
   1091     return 0;
   1092   else {
   1093     if (strcmp(message, "off") == 0)
   1094       lua_setwarnf(L, warnfoff, L);  /* turn warnings off */
   1095     else if (strcmp(message, "on") == 0)
   1096       lua_setwarnf(L, warnfon, L);   /* turn warnings on */
   1097     return 1;  /* it was a control message */
   1098   }
   1099 }
   1100 
   1101 
   1102 static void warnfoff (void *ud, const char *message, int tocont) {
   1103   checkcontrol((lua_State *)ud, message, tocont);
   1104 }
   1105 
   1106 
   1107 /*
   1108 ** Writes the message and handle 'tocont', finishing the message
   1109 ** if needed and setting the next warn function.
   1110 */
   1111 static void warnfcont (void *ud, const char *message, int tocont) {
   1112   lua_State *L = (lua_State *)ud;
   1113   lua_writestringerror("%s", message);  /* write message */
   1114   if (tocont)  /* not the last part? */
   1115     lua_setwarnf(L, warnfcont, L);  /* to be continued */
   1116   else {  /* last part */
   1117     lua_writestringerror("%s", "\n");  /* finish message with end-of-line */
   1118     lua_setwarnf(L, warnfon, L);  /* next call is a new message */
   1119   }
   1120 }
   1121 
   1122 
   1123 static void warnfon (void *ud, const char *message, int tocont) {
   1124   if (checkcontrol((lua_State *)ud, message, tocont))  /* control message? */
   1125     return;  /* nothing else to be done */
   1126   lua_writestringerror("%s", "Lua warning: ");  /* start a new warning */
   1127   warnfcont(ud, message, tocont);  /* finish processing */
   1128 }
   1129 
   1130 
   1131 
   1132 /*
   1133 ** A function to compute an unsigned int with some level of
   1134 ** randomness. Rely on Address Space Layout Randomization (if present)
   1135 ** and the current time.
   1136 */
   1137 #if !defined(luai_makeseed)
   1138 
   1139 #include <time.h>
   1140 
   1141 
   1142 /* Size for the buffer, in bytes */
   1143 #define BUFSEEDB	(sizeof(void*) + sizeof(time_t))
   1144 
   1145 /* Size for the buffer in int's, rounded up */
   1146 #define BUFSEED		((BUFSEEDB + sizeof(int) - 1) / sizeof(int))
   1147 
   1148 /*
   1149 ** Copy the contents of variable 'v' into the buffer pointed by 'b'.
   1150 ** (The '&b[0]' disguises 'b' to fix an absurd warning from clang.)
   1151 */
   1152 #define addbuff(b,v)	(memcpy(&b[0], &(v), sizeof(v)), b += sizeof(v))
   1153 
   1154 
   1155 static unsigned int luai_makeseed (void) {
   1156   unsigned int buff[BUFSEED];
   1157   unsigned int res;
   1158   unsigned int i;
   1159   time_t t = time(NULL);
   1160   char *b = (char*)buff;
   1161   addbuff(b, b);  /* local variable's address */
   1162   addbuff(b, t);  /* time */
   1163   /* fill (rare but possible) remain of the buffer with zeros */
   1164   memset(b, 0, sizeof(buff) - BUFSEEDB);
   1165   res = buff[0];
   1166   for (i = 1; i < BUFSEED; i++)
   1167     res ^= (res >> 3) + (res << 7) + buff[i];
   1168   return res;
   1169 }
   1170 
   1171 #endif
   1172 
   1173 
   1174 LUALIB_API unsigned int luaL_makeseed (lua_State *L) {
   1175   (void)L;  /* unused */
   1176   return luai_makeseed();
   1177 }
   1178 
   1179 
   1180 LUALIB_API lua_State *luaL_newstate (void) {
   1181   lua_State *L = lua_newstate(l_alloc, NULL, luai_makeseed());
   1182   if (l_likely(L)) {
   1183     lua_atpanic(L, &panic);
   1184     lua_setwarnf(L, warnfoff, L);  /* default is warnings off */
   1185   }
   1186   return L;
   1187 }
   1188 
   1189 
   1190 LUALIB_API void luaL_checkversion_ (lua_State *L, lua_Number ver, size_t sz) {
   1191   lua_Number v = lua_version(L);
   1192   if (sz != LUAL_NUMSIZES)  /* check numeric types */
   1193     luaL_error(L, "core and library have incompatible numeric types");
   1194   else if (v != ver)
   1195     luaL_error(L, "version mismatch: app. needs %f, Lua core provides %f",
   1196                   (LUAI_UACNUMBER)ver, (LUAI_UACNUMBER)v);
   1197 }
   1198