liblua/lmem.c

   1 /*
   2 ** $Id: lmem.c,v 1.84 2012/05/23 15:41:53 roberto Exp $
   3 ** Interface to Memory Manager
   4 ** See Copyright Notice in lua.h
   5 */
   6
   7
   8 #include <stddef.h>
   9
  10 #define lmem_c
  11 #define LUA_CORE
  12
  13 #include "lua.h"
  14
  15 #include "ldebug.h"
  16 #include "ldo.h"
  17 #include "lgc.h"
  18 #include "lmem.h"
  19 #include "lobject.h"
  20 #include "lstate.h"
  21
  22
  23
  24 /*
  25 ** About the realloc function:
  26 ** void * frealloc (void *ud, void *ptr, size_t osize, size_t nsize);
  27 ** (`osize' is the old size, `nsize' is the new size)
  28 **
  29 ** * frealloc(ud, NULL, x, s) creates a new block of size `s' (no
  30 ** matter 'x').
  31 **
  32 ** * frealloc(ud, p, x, 0) frees the block `p'
  33 ** (in this specific case, frealloc must return NULL);
  34 ** particularly, frealloc(ud, NULL, 0, 0) does nothing
  35 ** (which is equivalent to free(NULL) in ANSI C)
  36 **
  37 ** frealloc returns NULL if it cannot create or reallocate the area
  38 ** (any reallocation to an equal or smaller size cannot fail!)
  39 */
  40
  41
  42
  43 #define MINSIZEARRAY    4
  44
  45
  46 void *luaM_growaux_ (lua_State *L, void *block, int *size, size_t size_elems,
  47                      int limit, const char *what) {
  48   void *newblock;
  49   int newsize;
  50   if (*size >= limit/2) {  /* cannot double it? */
  51     if (*size >= limit)  /* cannot grow even a little? */
  52       luaG_runerror(L, "too many %s (limit is %d)", what, limit);
  53     newsize = limit;  /* still have at least one free place */
  54   }
  55   else {
  56     newsize = (*size)*2;
  57     if (newsize < MINSIZEARRAY)
  58       newsize = MINSIZEARRAY;  /* minimum size */
  59   }
  60   newblock = luaM_reallocv(L, block, *size, newsize, size_elems);
  61   *size = newsize;  /* update only when everything else is OK */
  62   return newblock;
  63 }
  64
  65
  66 l_noret luaM_toobig (lua_State *L) {
  67   luaG_runerror(L, "memory allocation error: block too big");
  68 }
  69
  70
  71
  72 /*
  73 ** generic allocation routine.
  74 */
  75 void *luaM_realloc_ (lua_State *L, void *block, size_t osize, size_t nsize) {
  76   void *newblock;
  77   global_State *g = G(L);
  78   size_t realosize = (block) ? osize : 0;
  79   lua_assert((realosize == 0) == (block == NULL));
  80 #if defined(HARDMEMTESTS)
  81   if (nsize > realosize && g->gcrunning)
  82     luaC_fullgc(L, 1);  /* force a GC whenever possible */
  83 #endif
  84   newblock = (*g->frealloc)(g->ud, block, osize, nsize);
  85   if (newblock == NULL && nsize > 0) {
  86     api_check(L, nsize > realosize,
  87                  "realloc cannot fail when shrinking a block");
  88     if (g->gcrunning) {
  89       luaC_fullgc(L, 1);  /* try to free some memory... */
  90       newblock = (*g->frealloc)(g->ud, block, osize, nsize);  /* try again */
  91     }
  92     if (newblock == NULL)
  93       luaD_throw(L, LUA_ERRMEM);
  94   }
  95   lua_assert((nsize == 0) == (newblock == NULL));
  96   g->GCdebt = (g->GCdebt + nsize) - realosize;
  97   return newblock;
  98 }
  99