lua

lmem.c (6245B)

---

 /*
 ** $Id: lmem.c $
 ** Interface to Memory Manager
 ** See Copyright Notice in lua.h
 */
 
 #define lmem_c
 #define LUA_CORE
 
 #include "lprefix.h"
 
 
 #include <stddef.h>
 
 #include "lua.h"
 
 #include "ldebug.h"
 #include "ldo.h"
 #include "lgc.h"
 #include "lmem.h"
 #include "lobject.h"
 #include "lstate.h"
 
 
 
 /*
 ** About the realloc function:
 ** void *frealloc (void *ud, void *ptr, size_t osize, size_t nsize);
 ** ('osize' is the old size, 'nsize' is the new size)
 **
 ** - frealloc(ud, p, x, 0) frees the block 'p' and returns NULL.
 ** Particularly, frealloc(ud, NULL, 0, 0) does nothing,
 ** which is equivalent to free(NULL) in ISO C.
 **
 ** - frealloc(ud, NULL, x, s) creates a new block of size 's'
 ** (no matter 'x'). Returns NULL if it cannot create the new block.
 **
 ** - otherwise, frealloc(ud, b, x, y) reallocates the block 'b' from
 ** size 'x' to size 'y'. Returns NULL if it cannot reallocate the
 ** block to the new size.
 */
 
 
 /*
 ** Macro to call the allocation function.
 */
 #define callfrealloc(g,block,os,ns)    ((*g->frealloc)(g->ud, block, os, ns))
 
 
 /*
 ** When an allocation fails, it will try again after an emergency
 ** collection, except when it cannot run a collection.  The GC should
 ** not be called while the state is not fully built, as the collector
 ** is not yet fully initialized. Also, it should not be called when
 ** 'gcstopem' is true, because then the interpreter is in the middle of
 ** a collection step.
 */
 #define cantryagain(g)	(completestate(g) && !g->gcstopem)
 
 
 
 
 #if defined(EMERGENCYGCTESTS)
 /*
 ** First allocation will fail except when freeing a block (frees never
 ** fail) and when it cannot try again; this fail will trigger 'tryagain'
 ** and a full GC cycle at every allocation.
 */
 static void *firsttry (global_State *g, void *block, size_t os, size_t ns) {
   if (ns > 0 && cantryagain(g))
     return NULL;  /* fail */
   else  /* normal allocation */
     return callfrealloc(g, block, os, ns);
 }
 #else
 #define firsttry(g,block,os,ns)    callfrealloc(g, block, os, ns)
 #endif
 
 
 
 
 
 /*
 ** {==================================================================
 ** Functions to allocate/deallocate arrays for the Parser
 ** ===================================================================
 */
 
 /*
 ** Minimum size for arrays during parsing, to avoid overhead of
 ** reallocating to size 1, then 2, and then 4. All these arrays
 ** will be reallocated to exact sizes or erased when parsing ends.
 */
 #define MINSIZEARRAY	4
 
 
 void *luaM_growaux_ (lua_State *L, void *block, int nelems, int *psize,
                      unsigned size_elems, int limit, const char *what) {
   void *newblock;
   int size = *psize;
   if (nelems + 1 <= size)  /* does one extra element still fit? */
     return block;  /* nothing to be done */
   if (size >= limit / 2) {  /* cannot double it? */
     if (l_unlikely(size >= limit))  /* cannot grow even a little? */
       luaG_runerror(L, "too many %s (limit is %d)", what, limit);
     size = limit;  /* still have at least one free place */
   }
   else {
     size *= 2;
     if (size < MINSIZEARRAY)
       size = MINSIZEARRAY;  /* minimum size */
   }
   lua_assert(nelems + 1 <= size && size <= limit);
   /* 'limit' ensures that multiplication will not overflow */
   newblock = luaM_saferealloc_(L, block, cast_sizet(*psize) * size_elems,
                                          cast_sizet(size) * size_elems);
   *psize = size;  /* update only when everything else is OK */
   return newblock;
 }
 
 
 /*
 ** In prototypes, the size of the array is also its number of
 ** elements (to save memory). So, if it cannot shrink an array
 ** to its number of elements, the only option is to raise an
 ** error.
 */
 void *luaM_shrinkvector_ (lua_State *L, void *block, int *size,
                           int final_n, unsigned size_elem) {
   void *newblock;
   size_t oldsize = cast_sizet(*size) * size_elem;
   size_t newsize = cast_sizet(final_n) * size_elem;
   lua_assert(newsize <= oldsize);
   newblock = luaM_saferealloc_(L, block, oldsize, newsize);
   *size = final_n;
   return newblock;
 }
 
 /* }================================================================== */
 
 
 l_noret luaM_toobig (lua_State *L) {
   luaG_runerror(L, "memory allocation error: block too big");
 }
 
 
 /*
 ** Free memory
 */
 void luaM_free_ (lua_State *L, void *block, size_t osize) {
   global_State *g = G(L);
   lua_assert((osize == 0) == (block == NULL));
   callfrealloc(g, block, osize, 0);
   g->GCdebt += cast(l_mem, osize);
 }
 
 
 /*
 ** In case of allocation fail, this function will do an emergency
 ** collection to free some memory and then try the allocation again.
 */
 static void *tryagain (lua_State *L, void *block,
                        size_t osize, size_t nsize) {
   global_State *g = G(L);
   if (cantryagain(g)) {
     luaC_fullgc(L, 1);  /* try to free some memory... */
     return callfrealloc(g, block, osize, nsize);  /* try again */
   }
   else return NULL;  /* cannot run an emergency collection */
 }
 
 
 /*
 ** Generic allocation routine.
 */
 void *luaM_realloc_ (lua_State *L, void *block, size_t osize, size_t nsize) {
   void *newblock;
   global_State *g = G(L);
   lua_assert((osize == 0) == (block == NULL));
   newblock = firsttry(g, block, osize, nsize);
   if (l_unlikely(newblock == NULL && nsize > 0)) {
     newblock = tryagain(L, block, osize, nsize);
     if (newblock == NULL)  /* still no memory? */
       return NULL;  /* do not update 'GCdebt' */
   }
   lua_assert((nsize == 0) == (newblock == NULL));
   g->GCdebt -= cast(l_mem, nsize) - cast(l_mem, osize);
   return newblock;
 }
 
 
 void *luaM_saferealloc_ (lua_State *L, void *block, size_t osize,
                                                     size_t nsize) {
   void *newblock = luaM_realloc_(L, block, osize, nsize);
   if (l_unlikely(newblock == NULL && nsize > 0))  /* allocation failed? */
     luaM_error(L);
   return newblock;
 }
 
 
 void *luaM_malloc_ (lua_State *L, size_t size, int tag) {
   if (size == 0)
     return NULL;  /* that's all */
   else {
     global_State *g = G(L);
     void *newblock = firsttry(g, NULL, cast_sizet(tag), size);
     if (l_unlikely(newblock == NULL)) {
       newblock = tryagain(L, NULL, cast_sizet(tag), size);
       if (newblock == NULL)
         luaM_error(L);
     }
     g->GCdebt -= cast(l_mem, size);
     return newblock;
   }
 }