lua

lauxlib.c (35966B)

---

 /*
 ** $Id: lauxlib.c $
 ** Auxiliary functions for building Lua libraries
 ** See Copyright Notice in lua.h
 */
 
 #define lauxlib_c
 #define LUA_LIB
 
 #include "lprefix.h"
 
 
 #include <errno.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 
 /*
 ** This file uses only the official API of Lua.
 ** Any function declared here could be written as an application function.
 */
 
 #include "lua.h"
 
 #include "lauxlib.h"
 #include "llimits.h"
 
 
 /*
 ** {======================================================
 ** Traceback
 ** =======================================================
 */
 
 
 #define LEVELS1	10	/* size of the first part of the stack */
 #define LEVELS2	11	/* size of the second part of the stack */
 
 
 
 /*
 ** Search for 'objidx' in table at index -1. ('objidx' must be an
 ** absolute index.) Return 1 + string at top if it found a good name.
 */
 static int findfield (lua_State *L, int objidx, int level) {
   if (level == 0 || !lua_istable(L, -1))
     return 0;  /* not found */
   lua_pushnil(L);  /* start 'next' loop */
   while (lua_next(L, -2)) {  /* for each pair in table */
     if (lua_type(L, -2) == LUA_TSTRING) {  /* ignore non-string keys */
       if (lua_rawequal(L, objidx, -1)) {  /* found object? */
         lua_pop(L, 1);  /* remove value (but keep name) */
         return 1;
       }
       else if (findfield(L, objidx, level - 1)) {  /* try recursively */
         /* stack: lib_name, lib_table, field_name (top) */
         lua_pushliteral(L, ".");  /* place '.' between the two names */
         lua_replace(L, -3);  /* (in the slot occupied by table) */
         lua_concat(L, 3);  /* lib_name.field_name */
         return 1;
       }
     }
     lua_pop(L, 1);  /* remove value */
   }
   return 0;  /* not found */
 }
 
 
 /*
 ** Search for a name for a function in all loaded modules
 */
 static int pushglobalfuncname (lua_State *L, lua_Debug *ar) {
   int top = lua_gettop(L);
   lua_getinfo(L, "f", ar);  /* push function */
   lua_getfield(L, LUA_REGISTRYINDEX, LUA_LOADED_TABLE);
   luaL_checkstack(L, 6, "not enough stack");  /* slots for 'findfield' */
   if (findfield(L, top + 1, 2)) {
     const char *name = lua_tostring(L, -1);
     if (strncmp(name, LUA_GNAME ".", 3) == 0) {  /* name start with '_G.'? */
       lua_pushstring(L, name + 3);  /* push name without prefix */
       lua_remove(L, -2);  /* remove original name */
     }
     lua_copy(L, -1, top + 1);  /* copy name to proper place */
     lua_settop(L, top + 1);  /* remove table "loaded" and name copy */
     return 1;
   }
   else {
     lua_settop(L, top);  /* remove function and global table */
     return 0;
   }
 }
 
 
 static void pushfuncname (lua_State *L, lua_Debug *ar) {
   if (pushglobalfuncname(L, ar)) {  /* try first a global name */
     lua_pushfstring(L, "function '%s'", lua_tostring(L, -1));
     lua_remove(L, -2);  /* remove name */
   }
   else if (*ar->namewhat != '\0')  /* is there a name from code? */
     lua_pushfstring(L, "%s '%s'", ar->namewhat, ar->name);  /* use it */
   else if (*ar->what == 'm')  /* main? */
       lua_pushliteral(L, "main chunk");
   else if (*ar->what != 'C')  /* for Lua functions, use <file:line> */
     lua_pushfstring(L, "function <%s:%d>", ar->short_src, ar->linedefined);
   else  /* nothing left... */
     lua_pushliteral(L, "?");
 }
 
 
 static int lastlevel (lua_State *L) {
   lua_Debug ar;
   int li = 1, le = 1;
   /* find an upper bound */
   while (lua_getstack(L, le, &ar)) { li = le; le *= 2; }
   /* do a binary search */
   while (li < le) {
     int m = (li + le)/2;
     if (lua_getstack(L, m, &ar)) li = m + 1;
     else le = m;
   }
   return le - 1;
 }
 
 
 LUALIB_API void luaL_traceback (lua_State *L, lua_State *L1,
                                 const char *msg, int level) {
   luaL_Buffer b;
   lua_Debug ar;
   int last = lastlevel(L1);
   int limit2show = (last - level > LEVELS1 + LEVELS2) ? LEVELS1 : -1;
   luaL_buffinit(L, &b);
   if (msg) {
     luaL_addstring(&b, msg);
     luaL_addchar(&b, '\n');
   }
   luaL_addstring(&b, "stack traceback:");
   while (lua_getstack(L1, level++, &ar)) {
     if (limit2show-- == 0) {  /* too many levels? */
       int n = last - level - LEVELS2 + 1;  /* number of levels to skip */
       lua_pushfstring(L, "\n\t...\t(skipping %d levels)", n);
       luaL_addvalue(&b);  /* add warning about skip */
       level += n;  /* and skip to last levels */
     }
     else {
       lua_getinfo(L1, "Slnt", &ar);
       if (ar.currentline <= 0)
         lua_pushfstring(L, "\n\t%s: in ", ar.short_src);
       else
         lua_pushfstring(L, "\n\t%s:%d: in ", ar.short_src, ar.currentline);
       luaL_addvalue(&b);
       pushfuncname(L, &ar);
       luaL_addvalue(&b);
       if (ar.istailcall)
         luaL_addstring(&b, "\n\t(...tail calls...)");
     }
   }
   luaL_pushresult(&b);
 }
 
 /* }====================================================== */
 
 
 /*
 ** {======================================================
 ** Error-report functions
 ** =======================================================
 */
 
 LUALIB_API int luaL_argerror (lua_State *L, int arg, const char *extramsg) {
   lua_Debug ar;
   const char *argword;
   if (!lua_getstack(L, 0, &ar))  /* no stack frame? */
     return luaL_error(L, "bad argument #%d (%s)", arg, extramsg);
   lua_getinfo(L, "nt", &ar);
   if (arg <= ar.extraargs)  /* error in an extra argument? */
     argword =  "extra argument";
   else {
     arg -= ar.extraargs;  /* do not count extra arguments */
     if (strcmp(ar.namewhat, "method") == 0) {  /* colon syntax? */
       arg--;  /* do not count (extra) self argument */
       if (arg == 0)  /* error in self argument? */
         return luaL_error(L, "calling '%s' on bad self (%s)",
                                ar.name, extramsg);
       /* else go through; error in a regular argument */
     }
     argword = "argument";
   }
   if (ar.name == NULL)
     ar.name = (pushglobalfuncname(L, &ar)) ? lua_tostring(L, -1) : "?";
   return luaL_error(L, "bad %s #%d to '%s' (%s)",
                        argword, arg, ar.name, extramsg);
 }
 
 
 LUALIB_API int luaL_typeerror (lua_State *L, int arg, const char *tname) {
   const char *msg;
   const char *typearg;  /* name for the type of the actual argument */
   if (luaL_getmetafield(L, arg, "__name") == LUA_TSTRING)
     typearg = lua_tostring(L, -1);  /* use the given type name */
   else if (lua_type(L, arg) == LUA_TLIGHTUSERDATA)
     typearg = "light userdata";  /* special name for messages */
   else
     typearg = luaL_typename(L, arg);  /* standard name */
   msg = lua_pushfstring(L, "%s expected, got %s", tname, typearg);
   return luaL_argerror(L, arg, msg);
 }
 
 
 static void tag_error (lua_State *L, int arg, int tag) {
   luaL_typeerror(L, arg, lua_typename(L, tag));
 }
 
 
 /*
 ** The use of 'lua_pushfstring' ensures this function does not
 ** need reserved stack space when called.
 */
 LUALIB_API void luaL_where (lua_State *L, int level) {
   lua_Debug ar;
   if (lua_getstack(L, level, &ar)) {  /* check function at level */
     lua_getinfo(L, "Sl", &ar);  /* get info about it */
     if (ar.currentline > 0) {  /* is there info? */
       lua_pushfstring(L, "%s:%d: ", ar.short_src, ar.currentline);
       return;
     }
   }
   lua_pushfstring(L, "");  /* else, no information available... */
 }
 
 
 /*
 ** Again, the use of 'lua_pushvfstring' ensures this function does
 ** not need reserved stack space when called. (At worst, it generates
 ** a memory error instead of the given message.)
 */
 LUALIB_API int luaL_error (lua_State *L, const char *fmt, ...) {
   va_list argp;
   va_start(argp, fmt);
   luaL_where(L, 1);
   lua_pushvfstring(L, fmt, argp);
   va_end(argp);
   lua_concat(L, 2);
   return lua_error(L);
 }
 
 
 LUALIB_API int luaL_fileresult (lua_State *L, int stat, const char *fname) {
   int en = errno;  /* calls to Lua API may change this value */
   if (stat) {
     lua_pushboolean(L, 1);
     return 1;
   }
   else {
     const char *msg;
     luaL_pushfail(L);
     msg = (en != 0) ? strerror(en) : "(no extra info)";
     if (fname)
       lua_pushfstring(L, "%s: %s", fname, msg);
     else
       lua_pushstring(L, msg);
     lua_pushinteger(L, en);
     return 3;
   }
 }
 
 
 #if !defined(l_inspectstat)	/* { */
 
 #if defined(LUA_USE_POSIX)
 
 #include <sys/wait.h>
 
 /*
 ** use appropriate macros to interpret 'pclose' return status
 */
 #define l_inspectstat(stat,what)  \
    if (WIFEXITED(stat)) { stat = WEXITSTATUS(stat); } \
    else if (WIFSIGNALED(stat)) { stat = WTERMSIG(stat); what = "signal"; }
 
 #else
 
 #define l_inspectstat(stat,what)  /* no op */
 
 #endif
 
 #endif				/* } */
 
 
 LUALIB_API int luaL_execresult (lua_State *L, int stat) {
   if (stat != 0 && errno != 0)  /* error with an 'errno'? */
     return luaL_fileresult(L, 0, NULL);
   else {
     const char *what = "exit";  /* type of termination */
     l_inspectstat(stat, what);  /* interpret result */
     if (*what == 'e' && stat == 0)  /* successful termination? */
       lua_pushboolean(L, 1);
     else
       luaL_pushfail(L);
     lua_pushstring(L, what);
     lua_pushinteger(L, stat);
     return 3;  /* return true/fail,what,code */
   }
 }
 
 /* }====================================================== */
 
 
 
 /*
 ** {======================================================
 ** Userdata's metatable manipulation
 ** =======================================================
 */
 
 LUALIB_API int luaL_newmetatable (lua_State *L, const char *tname) {
   if (luaL_getmetatable(L, tname) != LUA_TNIL)  /* name already in use? */
     return 0;  /* leave previous value on top, but return 0 */
   lua_pop(L, 1);
   lua_createtable(L, 0, 2);  /* create metatable */
   lua_pushstring(L, tname);
   lua_setfield(L, -2, "__name");  /* metatable.__name = tname */
   lua_pushvalue(L, -1);
   lua_setfield(L, LUA_REGISTRYINDEX, tname);  /* registry.name = metatable */
   return 1;
 }
 
 
 LUALIB_API void luaL_setmetatable (lua_State *L, const char *tname) {
   luaL_getmetatable(L, tname);
   lua_setmetatable(L, -2);
 }
 
 
 LUALIB_API void *luaL_testudata (lua_State *L, int ud, const char *tname) {
   void *p = lua_touserdata(L, ud);
   if (p != NULL) {  /* value is a userdata? */
     if (lua_getmetatable(L, ud)) {  /* does it have a metatable? */
       luaL_getmetatable(L, tname);  /* get correct metatable */
       if (!lua_rawequal(L, -1, -2))  /* not the same? */
         p = NULL;  /* value is a userdata with wrong metatable */
       lua_pop(L, 2);  /* remove both metatables */
       return p;
     }
   }
   return NULL;  /* value is not a userdata with a metatable */
 }
 
 
 LUALIB_API void *luaL_checkudata (lua_State *L, int ud, const char *tname) {
   void *p = luaL_testudata(L, ud, tname);
   luaL_argexpected(L, p != NULL, ud, tname);
   return p;
 }
 
 /* }====================================================== */
 
 
 /*
 ** {======================================================
 ** Argument check functions
 ** =======================================================
 */
 
 LUALIB_API int luaL_checkoption (lua_State *L, int arg, const char *def,
                                  const char *const lst[]) {
   const char *name = (def) ? luaL_optstring(L, arg, def) :
                              luaL_checkstring(L, arg);
   int i;
   for (i=0; lst[i]; i++)
     if (strcmp(lst[i], name) == 0)
       return i;
   return luaL_argerror(L, arg,
                        lua_pushfstring(L, "invalid option '%s'", name));
 }
 
 
 /*
 ** Ensures the stack has at least 'space' extra slots, raising an error
 ** if it cannot fulfill the request. (The error handling needs a few
 ** extra slots to format the error message. In case of an error without
 ** this extra space, Lua will generate the same 'stack overflow' error,
 ** but without 'msg'.)
 */
 LUALIB_API void luaL_checkstack (lua_State *L, int space, const char *msg) {
   if (l_unlikely(!lua_checkstack(L, space))) {
     if (msg)
       luaL_error(L, "stack overflow (%s)", msg);
     else
       luaL_error(L, "stack overflow");
   }
 }
 
 
 LUALIB_API void luaL_checktype (lua_State *L, int arg, int t) {
   if (l_unlikely(lua_type(L, arg) != t))
     tag_error(L, arg, t);
 }
 
 
 LUALIB_API void luaL_checkany (lua_State *L, int arg) {
   if (l_unlikely(lua_type(L, arg) == LUA_TNONE))
     luaL_argerror(L, arg, "value expected");
 }
 
 
 LUALIB_API const char *luaL_checklstring (lua_State *L, int arg, size_t *len) {
   const char *s = lua_tolstring(L, arg, len);
   if (l_unlikely(!s)) tag_error(L, arg, LUA_TSTRING);
   return s;
 }
 
 
 LUALIB_API const char *luaL_optlstring (lua_State *L, int arg,
                                         const char *def, size_t *len) {
   if (lua_isnoneornil(L, arg)) {
     if (len)
       *len = (def ? strlen(def) : 0);
     return def;
   }
   else return luaL_checklstring(L, arg, len);
 }
 
 
 LUALIB_API lua_Number luaL_checknumber (lua_State *L, int arg) {
   int isnum;
   lua_Number d = lua_tonumberx(L, arg, &isnum);
   if (l_unlikely(!isnum))
     tag_error(L, arg, LUA_TNUMBER);
   return d;
 }
 
 
 LUALIB_API lua_Number luaL_optnumber (lua_State *L, int arg, lua_Number def) {
   return luaL_opt(L, luaL_checknumber, arg, def);
 }
 
 
 static void interror (lua_State *L, int arg) {
   if (lua_isnumber(L, arg))
     luaL_argerror(L, arg, "number has no integer representation");
   else
     tag_error(L, arg, LUA_TNUMBER);
 }
 
 
 LUALIB_API lua_Integer luaL_checkinteger (lua_State *L, int arg) {
   int isnum;
   lua_Integer d = lua_tointegerx(L, arg, &isnum);
   if (l_unlikely(!isnum)) {
     interror(L, arg);
   }
   return d;
 }
 
 
 LUALIB_API lua_Integer luaL_optinteger (lua_State *L, int arg,
                                                       lua_Integer def) {
   return luaL_opt(L, luaL_checkinteger, arg, def);
 }
 
 /* }====================================================== */
 
 
 /*
 ** {======================================================
 ** Generic Buffer manipulation
 ** =======================================================
 */
 
 /* userdata to box arbitrary data */
 typedef struct UBox {
   void *box;
   size_t bsize;
 } UBox;
 
 
 /* Resize the buffer used by a box. Optimize for the common case of
 ** resizing to the old size. (For instance, __gc will resize the box
 ** to 0 even after it was closed. 'pushresult' may also resize it to a
 ** final size that is equal to the one set when the buffer was created.)
 */
 static void *resizebox (lua_State *L, int idx, size_t newsize) {
   UBox *box = (UBox *)lua_touserdata(L, idx);
   if (box->bsize == newsize)  /* not changing size? */
     return box->box;  /* keep the buffer */
   else {
     void *ud;
     lua_Alloc allocf = lua_getallocf(L, &ud);
     void *temp = allocf(ud, box->box, box->bsize, newsize);
     if (l_unlikely(temp == NULL && newsize > 0)) {  /* allocation error? */
       lua_pushliteral(L, "not enough memory");
       lua_error(L);  /* raise a memory error */
     }
     box->box = temp;
     box->bsize = newsize;
     return temp;
   }
 }
 
 
 static int boxgc (lua_State *L) {
   resizebox(L, 1, 0);
   return 0;
 }
 
 
 static const luaL_Reg boxmt[] = {  /* box metamethods */
   {"__gc", boxgc},
   {"__close", boxgc},
   {NULL, NULL}
 };
 
 
 static void newbox (lua_State *L) {
   UBox *box = (UBox *)lua_newuserdatauv(L, sizeof(UBox), 0);
   box->box = NULL;
   box->bsize = 0;
   if (luaL_newmetatable(L, "_UBOX*"))  /* creating metatable? */
     luaL_setfuncs(L, boxmt, 0);  /* set its metamethods */
   lua_setmetatable(L, -2);
 }
 
 
 /*
 ** check whether buffer is using a userdata on the stack as a temporary
 ** buffer
 */
 #define buffonstack(B)	((B)->b != (B)->init.b)
 
 
 /*
 ** Whenever buffer is accessed, slot 'idx' must either be a box (which
 ** cannot be NULL) or it is a placeholder for the buffer.
 */
 #define checkbufferlevel(B,idx)  \
   lua_assert(buffonstack(B) ? lua_touserdata(B->L, idx) != NULL  \
                             : lua_touserdata(B->L, idx) == (void*)B)
 
 
 /*
 ** Compute new size for buffer 'B', enough to accommodate extra 'sz'
 ** bytes plus one for a terminating zero. (The test for "not big enough"
 ** also gets the case when the computation of 'newsize' overflows.)
 */
 static size_t newbuffsize (luaL_Buffer *B, size_t sz) {
   size_t newsize = (B->size / 2) * 3;  /* buffer size * 1.5 */
   if (l_unlikely(sz > MAX_SIZE - B->n - 1))
     return cast_sizet(luaL_error(B->L, "resulting string too large"));
   if (newsize < B->n + sz + 1 || newsize > MAX_SIZE) {
     /* newsize was not big enough or too big */
     newsize = B->n + sz + 1;
   }
   return newsize;
 }
 
 
 /*
 ** Returns a pointer to a free area with at least 'sz' bytes in buffer
 ** 'B'. 'boxidx' is the relative position in the stack where is the
 ** buffer's box or its placeholder.
 */
 static char *prepbuffsize (luaL_Buffer *B, size_t sz, int boxidx) {
   checkbufferlevel(B, boxidx);
   if (B->size - B->n >= sz)  /* enough space? */
     return B->b + B->n;
   else {
     lua_State *L = B->L;
     char *newbuff;
     size_t newsize = newbuffsize(B, sz);
     /* create larger buffer */
     if (buffonstack(B))  /* buffer already has a box? */
       newbuff = (char *)resizebox(L, boxidx, newsize);  /* resize it */
     else {  /* no box yet */
       lua_remove(L, boxidx);  /* remove placeholder */
       newbox(L);  /* create a new box */
       lua_insert(L, boxidx);  /* move box to its intended position */
       lua_toclose(L, boxidx);
       newbuff = (char *)resizebox(L, boxidx, newsize);
       memcpy(newbuff, B->b, B->n * sizeof(char));  /* copy original content */
     }
     B->b = newbuff;
     B->size = newsize;
     return newbuff + B->n;
   }
 }
 
 /*
 ** returns a pointer to a free area with at least 'sz' bytes
 */
 LUALIB_API char *luaL_prepbuffsize (luaL_Buffer *B, size_t sz) {
   return prepbuffsize(B, sz, -1);
 }
 
 
 LUALIB_API void luaL_addlstring (luaL_Buffer *B, const char *s, size_t l) {
   if (l > 0) {  /* avoid 'memcpy' when 's' can be NULL */
     char *b = prepbuffsize(B, l, -1);
     memcpy(b, s, l * sizeof(char));
     luaL_addsize(B, l);
   }
 }
 
 
 LUALIB_API void luaL_addstring (luaL_Buffer *B, const char *s) {
   luaL_addlstring(B, s, strlen(s));
 }
 
 
 LUALIB_API void luaL_pushresult (luaL_Buffer *B) {
   lua_State *L = B->L;
   checkbufferlevel(B, -1);
   if (!buffonstack(B))  /* using static buffer? */
     lua_pushlstring(L, B->b, B->n);  /* save result as regular string */
   else {  /* reuse buffer already allocated */
     UBox *box = (UBox *)lua_touserdata(L, -1);
     void *ud;
     lua_Alloc allocf = lua_getallocf(L, &ud);  /* function to free buffer */
     size_t len = B->n;  /* final string length */
     char *s;
     resizebox(L, -1, len + 1);  /* adjust box size to content size */
     s = (char*)box->box;  /* final buffer address */
     s[len] = '\0';  /* add ending zero */
     /* clear box, as Lua will take control of the buffer */
     box->bsize = 0;  box->box = NULL;
     lua_pushexternalstring(L, s, len, allocf, ud);
     lua_closeslot(L, -2);  /* close the box */
     lua_gc(L, LUA_GCSTEP, len);
   }
   lua_remove(L, -2);  /* remove box or placeholder from the stack */
 }
 
 
 LUALIB_API void luaL_pushresultsize (luaL_Buffer *B, size_t sz) {
   luaL_addsize(B, sz);
   luaL_pushresult(B);
 }
 
 
 /*
 ** 'luaL_addvalue' is the only function in the Buffer system where the
 ** box (if existent) is not on the top of the stack. So, instead of
 ** calling 'luaL_addlstring', it replicates the code using -2 as the
 ** last argument to 'prepbuffsize', signaling that the box is (or will
 ** be) below the string being added to the buffer. (Box creation can
 ** trigger an emergency GC, so we should not remove the string from the
 ** stack before we have the space guaranteed.)
 */
 LUALIB_API void luaL_addvalue (luaL_Buffer *B) {
   lua_State *L = B->L;
   size_t len;
   const char *s = lua_tolstring(L, -1, &len);
   char *b = prepbuffsize(B, len, -2);
   memcpy(b, s, len * sizeof(char));
   luaL_addsize(B, len);
   lua_pop(L, 1);  /* pop string */
 }
 
 
 LUALIB_API void luaL_buffinit (lua_State *L, luaL_Buffer *B) {
   B->L = L;
   B->b = B->init.b;
   B->n = 0;
   B->size = LUAL_BUFFERSIZE;
   lua_pushlightuserdata(L, (void*)B);  /* push placeholder */
 }
 
 
 LUALIB_API char *luaL_buffinitsize (lua_State *L, luaL_Buffer *B, size_t sz) {
   luaL_buffinit(L, B);
   return prepbuffsize(B, sz, -1);
 }
 
 /* }====================================================== */
 
 
 /*
 ** {======================================================
 ** Reference system
 ** =======================================================
 */
 
 /*
 ** The previously freed references form a linked list: t[1] is the index
 ** of a first free index, t[t[1]] is the index of the second element,
 ** etc. A zero signals the end of the list.
 */
 LUALIB_API int luaL_ref (lua_State *L, int t) {
   int ref;
   if (lua_isnil(L, -1)) {
     lua_pop(L, 1);  /* remove from stack */
     return LUA_REFNIL;  /* 'nil' has a unique fixed reference */
   }
   t = lua_absindex(L, t);
   if (lua_rawgeti(L, t, 1) == LUA_TNUMBER)  /* already initialized? */
     ref = (int)lua_tointeger(L, -1);  /* ref = t[1] */
   else {  /* first access */
     lua_assert(!lua_toboolean(L, -1));  /* must be nil or false */
     ref = 0;  /* list is empty */
     lua_pushinteger(L, 0);  /* initialize as an empty list */
     lua_rawseti(L, t, 1);  /* ref = t[1] = 0 */
   }
   lua_pop(L, 1);  /* remove element from stack */
   if (ref != 0) {  /* any free element? */
     lua_rawgeti(L, t, ref);  /* remove it from list */
     lua_rawseti(L, t, 1);  /* (t[1] = t[ref]) */
   }
   else  /* no free elements */
     ref = (int)lua_rawlen(L, t) + 1;  /* get a new reference */
   lua_rawseti(L, t, ref);
   return ref;
 }
 
 
 LUALIB_API void luaL_unref (lua_State *L, int t, int ref) {
   if (ref >= 0) {
     t = lua_absindex(L, t);
     lua_rawgeti(L, t, 1);
     lua_assert(lua_isinteger(L, -1));
     lua_rawseti(L, t, ref);  /* t[ref] = t[1] */
     lua_pushinteger(L, ref);
     lua_rawseti(L, t, 1);  /* t[1] = ref */
   }
 }
 
 /* }====================================================== */
 
 
 /*
 ** {======================================================
 ** Load functions
 ** =======================================================
 */
 
 typedef struct LoadF {
   unsigned n;  /* number of pre-read characters */
   FILE *f;  /* file being read */
   char buff[BUFSIZ];  /* area for reading file */
 } LoadF;
 
 
 static const char *getF (lua_State *L, void *ud, size_t *size) {
   LoadF *lf = (LoadF *)ud;
   (void)L;  /* not used */
   if (lf->n > 0) {  /* are there pre-read characters to be read? */
     *size = lf->n;  /* return them (chars already in buffer) */
     lf->n = 0;  /* no more pre-read characters */
   }
   else {  /* read a block from file */
     /* 'fread' can return > 0 *and* set the EOF flag. If next call to
        'getF' called 'fread', it might still wait for user input.
        The next check avoids this problem. */
     if (feof(lf->f)) return NULL;
     *size = fread(lf->buff, 1, sizeof(lf->buff), lf->f);  /* read block */
   }
   return lf->buff;
 }
 
 
 static int errfile (lua_State *L, const char *what, int fnameindex) {
   int err = errno;
   const char *filename = lua_tostring(L, fnameindex) + 1;
   if (err != 0)
     lua_pushfstring(L, "cannot %s %s: %s", what, filename, strerror(err));
   else
     lua_pushfstring(L, "cannot %s %s", what, filename);
   lua_remove(L, fnameindex);
   return LUA_ERRFILE;
 }
 
 
 /*
 ** Skip an optional BOM at the start of a stream. If there is an
 ** incomplete BOM (the first character is correct but the rest is
 ** not), returns the first character anyway to force an error
 ** (as no chunk can start with 0xEF).
 */
 static int skipBOM (FILE *f) {
   int c = getc(f);  /* read first character */
   if (c == 0xEF && getc(f) == 0xBB && getc(f) == 0xBF)  /* correct BOM? */
     return getc(f);  /* ignore BOM and return next char */
   else  /* no (valid) BOM */
     return c;  /* return first character */
 }
 
 
 /*
 ** reads the first character of file 'f' and skips an optional BOM mark
 ** in its beginning plus its first line if it starts with '#'. Returns
 ** true if it skipped the first line.  In any case, '*cp' has the
 ** first "valid" character of the file (after the optional BOM and
 ** a first-line comment).
 */
 static int skipcomment (FILE *f, int *cp) {
   int c = *cp = skipBOM(f);
   if (c == '#') {  /* first line is a comment (Unix exec. file)? */
     do {  /* skip first line */
       c = getc(f);
     } while (c != EOF && c != '\n');
     *cp = getc(f);  /* next character after comment, if present */
     return 1;  /* there was a comment */
   }
   else return 0;  /* no comment */
 }
 
 
 LUALIB_API int luaL_loadfilex (lua_State *L, const char *filename,
                                              const char *mode) {
   LoadF lf;
   int status, readstatus;
   int c;
   int fnameindex = lua_gettop(L) + 1;  /* index of filename on the stack */
   if (filename == NULL) {
     lua_pushliteral(L, "=stdin");
     lf.f = stdin;
   }
   else {
     lua_pushfstring(L, "@%s", filename);
     errno = 0;
     lf.f = fopen(filename, "r");
     if (lf.f == NULL) return errfile(L, "open", fnameindex);
   }
   lf.n = 0;
   if (skipcomment(lf.f, &c))  /* read initial portion */
     lf.buff[lf.n++] = '\n';  /* add newline to correct line numbers */
   if (c == LUA_SIGNATURE[0]) {  /* binary file? */
     lf.n = 0;  /* remove possible newline */
     if (filename) {  /* "real" file? */
       errno = 0;
       lf.f = freopen(filename, "rb", lf.f);  /* reopen in binary mode */
       if (lf.f == NULL) return errfile(L, "reopen", fnameindex);
       skipcomment(lf.f, &c);  /* re-read initial portion */
     }
   }
   if (c != EOF)
     lf.buff[lf.n++] = cast_char(c);  /* 'c' is the first character */
   status = lua_load(L, getF, &lf, lua_tostring(L, -1), mode);
   readstatus = ferror(lf.f);
   errno = 0;  /* no useful error number until here */
   if (filename) fclose(lf.f);  /* close file (even in case of errors) */
   if (readstatus) {
     lua_settop(L, fnameindex);  /* ignore results from 'lua_load' */
     return errfile(L, "read", fnameindex);
   }
   lua_remove(L, fnameindex);
   return status;
 }
 
 
 typedef struct LoadS {
   const char *s;
   size_t size;
 } LoadS;
 
 
 static const char *getS (lua_State *L, void *ud, size_t *size) {
   LoadS *ls = (LoadS *)ud;
   (void)L;  /* not used */
   if (ls->size == 0) return NULL;
   *size = ls->size;
   ls->size = 0;
   return ls->s;
 }
 
 
 LUALIB_API int luaL_loadbufferx (lua_State *L, const char *buff, size_t size,
                                  const char *name, const char *mode) {
   LoadS ls;
   ls.s = buff;
   ls.size = size;
   return lua_load(L, getS, &ls, name, mode);
 }
 
 
 LUALIB_API int luaL_loadstring (lua_State *L, const char *s) {
   return luaL_loadbuffer(L, s, strlen(s), s);
 }
 
 /* }====================================================== */
 
 
 
 LUALIB_API int luaL_getmetafield (lua_State *L, int obj, const char *event) {
   if (!lua_getmetatable(L, obj))  /* no metatable? */
     return LUA_TNIL;
   else {
     int tt;
     lua_pushstring(L, event);
     tt = lua_rawget(L, -2);
     if (tt == LUA_TNIL)  /* is metafield nil? */
       lua_pop(L, 2);  /* remove metatable and metafield */
     else
       lua_remove(L, -2);  /* remove only metatable */
     return tt;  /* return metafield type */
   }
 }
 
 
 LUALIB_API int luaL_callmeta (lua_State *L, int obj, const char *event) {
   obj = lua_absindex(L, obj);
   if (luaL_getmetafield(L, obj, event) == LUA_TNIL)  /* no metafield? */
     return 0;
   lua_pushvalue(L, obj);
   lua_call(L, 1, 1);
   return 1;
 }
 
 
 LUALIB_API lua_Integer luaL_len (lua_State *L, int idx) {
   lua_Integer l;
   int isnum;
   lua_len(L, idx);
   l = lua_tointegerx(L, -1, &isnum);
   if (l_unlikely(!isnum))
     luaL_error(L, "object length is not an integer");
   lua_pop(L, 1);  /* remove object */
   return l;
 }
 
 
 LUALIB_API const char *luaL_tolstring (lua_State *L, int idx, size_t *len) {
   idx = lua_absindex(L,idx);
   if (luaL_callmeta(L, idx, "__tostring")) {  /* metafield? */
     if (!lua_isstring(L, -1))
       luaL_error(L, "'__tostring' must return a string");
   }
   else {
     switch (lua_type(L, idx)) {
       case LUA_TNUMBER: {
         char buff[LUA_N2SBUFFSZ];
         lua_numbertocstring(L, idx, buff);
         lua_pushstring(L, buff);
         break;
       }
       case LUA_TSTRING:
         lua_pushvalue(L, idx);
         break;
       case LUA_TBOOLEAN:
         lua_pushstring(L, (lua_toboolean(L, idx) ? "true" : "false"));
         break;
       case LUA_TNIL:
         lua_pushliteral(L, "nil");
         break;
       default: {
         int tt = luaL_getmetafield(L, idx, "__name");  /* try name */
         const char *kind = (tt == LUA_TSTRING) ? lua_tostring(L, -1) :
                                                  luaL_typename(L, idx);
         lua_pushfstring(L, "%s: %p", kind, lua_topointer(L, idx));
         if (tt != LUA_TNIL)
           lua_remove(L, -2);  /* remove '__name' */
         break;
       }
     }
   }
   return lua_tolstring(L, -1, len);
 }
 
 
 /*
 ** set functions from list 'l' into table at top - 'nup'; each
 ** function gets the 'nup' elements at the top as upvalues.
 ** Returns with only the table at the stack.
 */
 LUALIB_API void luaL_setfuncs (lua_State *L, const luaL_Reg *l, int nup) {
   luaL_checkstack(L, nup, "too many upvalues");
   for (; l->name != NULL; l++) {  /* fill the table with given functions */
     if (l->func == NULL)  /* placeholder? */
       lua_pushboolean(L, 0);
     else {
       int i;
       for (i = 0; i < nup; i++)  /* copy upvalues to the top */
         lua_pushvalue(L, -nup);
       lua_pushcclosure(L, l->func, nup);  /* closure with those upvalues */
     }
     lua_setfield(L, -(nup + 2), l->name);
   }
   lua_pop(L, nup);  /* remove upvalues */
 }
 
 
 /*
 ** ensure that stack[idx][fname] has a table and push that table
 ** into the stack
 */
 LUALIB_API int luaL_getsubtable (lua_State *L, int idx, const char *fname) {
   if (lua_getfield(L, idx, fname) == LUA_TTABLE)
     return 1;  /* table already there */
   else {
     lua_pop(L, 1);  /* remove previous result */
     idx = lua_absindex(L, idx);
     lua_newtable(L);
     lua_pushvalue(L, -1);  /* copy to be left at top */
     lua_setfield(L, idx, fname);  /* assign new table to field */
     return 0;  /* false, because did not find table there */
   }
 }
 
 
 /*
 ** Stripped-down 'require': After checking "loaded" table, calls 'openf'
 ** to open a module, registers the result in 'package.loaded' table and,
 ** if 'glb' is true, also registers the result in the global table.
 ** Leaves resulting module on the top.
 */
 LUALIB_API void luaL_requiref (lua_State *L, const char *modname,
                                lua_CFunction openf, int glb) {
   luaL_getsubtable(L, LUA_REGISTRYINDEX, LUA_LOADED_TABLE);
   lua_getfield(L, -1, modname);  /* LOADED[modname] */
   if (!lua_toboolean(L, -1)) {  /* package not already loaded? */
     lua_pop(L, 1);  /* remove field */
     lua_pushcfunction(L, openf);
     lua_pushstring(L, modname);  /* argument to open function */
     lua_call(L, 1, 1);  /* call 'openf' to open module */
     lua_pushvalue(L, -1);  /* make copy of module (call result) */
     lua_setfield(L, -3, modname);  /* LOADED[modname] = module */
   }
   lua_remove(L, -2);  /* remove LOADED table */
   if (glb) {
     lua_pushvalue(L, -1);  /* copy of module */
     lua_setglobal(L, modname);  /* _G[modname] = module */
   }
 }
 
 
 LUALIB_API void luaL_addgsub (luaL_Buffer *b, const char *s,
                                      const char *p, const char *r) {
   const char *wild;
   size_t l = strlen(p);
   while ((wild = strstr(s, p)) != NULL) {
     luaL_addlstring(b, s, ct_diff2sz(wild - s));  /* push prefix */
     luaL_addstring(b, r);  /* push replacement in place of pattern */
     s = wild + l;  /* continue after 'p' */
   }
   luaL_addstring(b, s);  /* push last suffix */
 }
 
 
 LUALIB_API const char *luaL_gsub (lua_State *L, const char *s,
                                   const char *p, const char *r) {
   luaL_Buffer b;
   luaL_buffinit(L, &b);
   luaL_addgsub(&b, s, p, r);
   luaL_pushresult(&b);
   return lua_tostring(L, -1);
 }
 
 
 static void *l_alloc (void *ud, void *ptr, size_t osize, size_t nsize) {
   (void)ud; (void)osize;  /* not used */
   if (nsize == 0) {
     free(ptr);
     return NULL;
   }
   else
     return realloc(ptr, nsize);
 }
 
 
 /*
 ** Standard panic function just prints an error message. The test
 ** with 'lua_type' avoids possible memory errors in 'lua_tostring'.
 */
 static int panic (lua_State *L) {
   const char *msg = (lua_type(L, -1) == LUA_TSTRING)
                   ? lua_tostring(L, -1)
                   : "error object is not a string";
   lua_writestringerror("PANIC: unprotected error in call to Lua API (%s)\n",
                         msg);
   return 0;  /* return to Lua to abort */
 }
 
 
 /*
 ** Warning functions:
 ** warnfoff: warning system is off
 ** warnfon: ready to start a new message
 ** warnfcont: previous message is to be continued
 */
 static void warnfoff (void *ud, const char *message, int tocont);
 static void warnfon (void *ud, const char *message, int tocont);
 static void warnfcont (void *ud, const char *message, int tocont);
 
 
 /*
 ** Check whether message is a control message. If so, execute the
 ** control or ignore it if unknown.
 */
 static int checkcontrol (lua_State *L, const char *message, int tocont) {
   if (tocont || *(message++) != '@')  /* not a control message? */
     return 0;
   else {
     if (strcmp(message, "off") == 0)
       lua_setwarnf(L, warnfoff, L);  /* turn warnings off */
     else if (strcmp(message, "on") == 0)
       lua_setwarnf(L, warnfon, L);   /* turn warnings on */
     return 1;  /* it was a control message */
   }
 }
 
 
 static void warnfoff (void *ud, const char *message, int tocont) {
   checkcontrol((lua_State *)ud, message, tocont);
 }
 
 
 /*
 ** Writes the message and handle 'tocont', finishing the message
 ** if needed and setting the next warn function.
 */
 static void warnfcont (void *ud, const char *message, int tocont) {
   lua_State *L = (lua_State *)ud;
   lua_writestringerror("%s", message);  /* write message */
   if (tocont)  /* not the last part? */
     lua_setwarnf(L, warnfcont, L);  /* to be continued */
   else {  /* last part */
     lua_writestringerror("%s", "\n");  /* finish message with end-of-line */
     lua_setwarnf(L, warnfon, L);  /* next call is a new message */
   }
 }
 
 
 static void warnfon (void *ud, const char *message, int tocont) {
   if (checkcontrol((lua_State *)ud, message, tocont))  /* control message? */
     return;  /* nothing else to be done */
   lua_writestringerror("%s", "Lua warning: ");  /* start a new warning */
   warnfcont(ud, message, tocont);  /* finish processing */
 }
 
 
 
 /*
 ** A function to compute an unsigned int with some level of
 ** randomness. Rely on Address Space Layout Randomization (if present)
 ** and the current time.
 */
 #if !defined(luai_makeseed)
 
 #include <time.h>
 
 
 /* Size for the buffer, in bytes */
 #define BUFSEEDB	(sizeof(void*) + sizeof(time_t))
 
 /* Size for the buffer in int's, rounded up */
 #define BUFSEED		((BUFSEEDB + sizeof(int) - 1) / sizeof(int))
 
 /*
 ** Copy the contents of variable 'v' into the buffer pointed by 'b'.
 ** (The '&b[0]' disguises 'b' to fix an absurd warning from clang.)
 */
 #define addbuff(b,v)	(memcpy(&b[0], &(v), sizeof(v)), b += sizeof(v))
 
 
 static unsigned int luai_makeseed (void) {
   unsigned int buff[BUFSEED];
   unsigned int res;
   unsigned int i;
   time_t t = time(NULL);
   char *b = (char*)buff;
   addbuff(b, b);  /* local variable's address */
   addbuff(b, t);  /* time */
   /* fill (rare but possible) remain of the buffer with zeros */
   memset(b, 0, sizeof(buff) - BUFSEEDB);
   res = buff[0];
   for (i = 1; i < BUFSEED; i++)
     res ^= (res >> 3) + (res << 7) + buff[i];
   return res;
 }
 
 #endif
 
 
 LUALIB_API unsigned int luaL_makeseed (lua_State *L) {
   (void)L;  /* unused */
   return luai_makeseed();
 }
 
 
 LUALIB_API lua_State *luaL_newstate (void) {
   lua_State *L = lua_newstate(l_alloc, NULL, luai_makeseed());
   if (l_likely(L)) {
     lua_atpanic(L, &panic);
     lua_setwarnf(L, warnfoff, L);  /* default is warnings off */
   }
   return L;
 }
 
 
 LUALIB_API void luaL_checkversion_ (lua_State *L, lua_Number ver, size_t sz) {
   lua_Number v = lua_version(L);
   if (sz != LUAL_NUMSIZES)  /* check numeric types */
     luaL_error(L, "core and library have incompatible numeric types");
   else if (v != ver)
     luaL_error(L, "version mismatch: app. needs %f, Lua core provides %f",
                   (LUAI_UACNUMBER)ver, (LUAI_UACNUMBER)v);
 }