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Tricks of the Windows Gam…ming Gurus (2nd Edition)
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Disc2.iso
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vc98
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crt
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src
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realloc.c
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C/C++ Source or Header
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1998-06-17
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18KB
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525 lines
/***
*realloc.c - Reallocate a block of memory in the heap
*
* Copyright (c) 1989-1997, Microsoft Corporation. All rights reserved.
*
*Purpose:
* Defines the realloc() and _expand() functions.
*
*******************************************************************************/
#ifdef WINHEAP
#include <cruntime.h>
#include <malloc.h>
#include <stdlib.h>
#include <string.h>
#include <winheap.h>
#include <windows.h>
#include <internal.h>
#include <mtdll.h>
#include <dbgint.h>
/***
*void *realloc(pblock, newsize) - reallocate a block of memory in the heap
*
*Purpose:
* Reallocates a block in the heap to newsize bytes. newsize may be
* either greater or less than the original size of the block. The
* reallocation may result in moving the block as well as changing
* the size. If the block is moved, the contents of the original block
* are copied over.
*
* Special ANSI Requirements:
*
* (1) realloc(NULL, newsize) is equivalent to malloc(newsize)
*
* (2) realloc(pblock, 0) is equivalent to free(pblock) (except that
* NULL is returned)
*
* (3) if the realloc() fails, the object pointed to by pblock is left
* unchanged
*
*Entry:
* void *pblock - pointer to block in the heap previously allocated
* by a call to malloc(), realloc() or _expand().
*
* size_t newsize - requested size for the re-allocated block
*
*Exit:
* Success: Pointer to the re-allocated memory block
* Failure: NULL
*
*Uses:
*
*Exceptions:
* If pblock does not point to a valid allocation block in the heap,
* realloc() will behave unpredictably and probably corrupt the heap.
*
*******************************************************************************/
void * __cdecl _realloc_base (void * pBlock, size_t newsize)
{
PHEADER pHeader;
void * pvReturn;
size_t oldsize;
// if ptr is NULL, call malloc
if (pBlock == NULL)
return(_malloc_base(newsize));
// if ptr is nonNULL and size is zero, call free and return NULL
if (newsize == 0)
{
_free_base(pBlock);
return(NULL);
}
for (;;) {
pvReturn = NULL;
if (newsize <= _HEAP_MAXREQ)
{
_mlock(_HEAP_LOCK);
// test if current block is in the small-block heap
if ((pHeader = __sbh_find_block(pBlock)) != NULL)
{
// if the new size is not over __sbh_threshold, attempt
// to reallocate within the small-block heap
if (newsize <= __sbh_threshold)
{
if (__sbh_resize_block(pHeader, pBlock, newsize))
pvReturn = pBlock;
else if ((pvReturn = __sbh_alloc_block(newsize)) != NULL)
{
oldsize = ((PENTRY)((char *)pBlock -
sizeof(int)))->sizeFront - 1;
memcpy(pvReturn, pBlock, __min(oldsize, newsize));
__sbh_free_block(pHeader, pBlock);
}
}
// If the reallocation has not been (successfully)
// performed in the small-block heap, try to allocate
// a new block with HeapAlloc.
if (pvReturn == NULL)
{
if (newsize == 0)
newsize = 1;
newsize = (newsize + BYTES_PER_PARA - 1) &
~(BYTES_PER_PARA - 1);
if ((pvReturn = HeapAlloc(_crtheap, 0, newsize)) != NULL)
{
oldsize = ((PENTRY)((char *)pBlock -
sizeof(int)))->sizeFront - 1;
memcpy(pvReturn, pBlock, __min(oldsize, newsize));
__sbh_free_block(pHeader, pBlock);
}
}
_munlock(_HEAP_LOCK);
}
else
{
_munlock(_HEAP_LOCK);
if (newsize == 0)
newsize = 1;
newsize = (newsize + BYTES_PER_PARA - 1) &
~(BYTES_PER_PARA - 1);
pvReturn = HeapReAlloc(_crtheap, 0, pBlock, newsize);
}
}
if ( pvReturn || _newmode == 0)
return pvReturn;
// call installed new handler
if (!_callnewh(newsize))
return NULL;
// new handler was successful -- try to allocate again
}
}
#else /* WINHEAP */
#include <cruntime.h>
#include <heap.h>
#include <malloc.h>
#include <mtdll.h>
#include <stddef.h>
#include <string.h>
#include <dbgint.h>
#if defined (_M_MPPC) || defined (_M_M68K)
#include <macos\memory.h> // Mac OS interface header
#endif /* defined (_M_MPPC) || defined (_M_M68K) */
/* useful macro to compute the size of an allocation block given both a
* pointer to the descriptor and a pointer to the user area of the block
* (more efficient variant of _BLKSIZE macro, given the extra information)
*/
#define BLKSZ(pdesc_m,pblock_m) ((unsigned)_ADDRESS((pdesc_m)->pnextdesc) - \
(unsigned)(pblock_m))
/* expand an allocation block, in place, up to or beyond a specified size
* by coalescing it with subsequent free blocks (if possible)
*/
static int __cdecl _heap_expand_block(_PBLKDESC, size_t *, size_t);
#if defined (_M_MPPC) || defined (_M_M68K)
extern Handle hHeapRegions;
extern int _heap_region_table_cur;
#endif /* defined (_M_MPPC) || defined (_M_M68K) */
/***
*void *realloc(void *pblock, size_t newsize) - reallocate a block of memory in
* the heap
*
*Purpose:
* Re-allocates a block in the heap to newsize bytes. newsize may be
* either greater or less than the original size of the block. The
* re-allocation may result in moving the block as well as changing
* the size. If the block is moved, the contents of the original block
* are copied over.
*
* Special ANSI Requirements:
*
* (1) realloc(NULL, newsize) is equivalent to malloc(newsize)
*
* (2) realloc(pblock, 0) is equivalent to free(pblock) (except that
* NULL is returned)
*
* (3) if the realloc() fails, the object pointed to by pblock is left
* unchanged
*
* Special Notes For Multi-thread: The heap is locked immediately prior
* to assigning pdesc. This is after special cases (1) and (2), listed
* above, are taken care of. The lock is released immediately prior to
* the final return statement.
*
*Entry:
* void *pblock - pointer to block in the heap previously allocated
* by a call to malloc(), realloc() or _expand().
*
* size_t newsize - requested size for the re-allocated block
*
*Exit:
* Success: Pointer to the re-allocated memory block
* Failure: NULL
*
*Uses:
*
*Exceptions:
* If pblock does not point to a valid allocation block in the heap,
* realloc() will behave unpredictably and probably corrupt the heap.
*
*******************************************************************************/
void * __cdecl _realloc_base (
REG1 void *pblock,
size_t newsize
)
{
REG2 _PBLKDESC pdesc;
_PBLKDESC pdesc2;
void *retp;
size_t oldsize;
size_t currsize;
/* special cases, handling mandated by ANSI
*/
if ( pblock == NULL )
/* just do a malloc of newsize bytes and return a pointer to
* the new block
*/
return( _malloc_base(newsize) );
if ( newsize == 0 ) {
/* free the block and return NULL
*/
_free_base(pblock);
return( NULL );
}
/* make newsize a valid allocation block size (i.e., round up to the
* nearest whole number of dwords)
*/
newsize = _ROUND2(newsize, _GRANULARITY);
/* if multi-thread support enabled, lock the heap here
*/
_mlock(_HEAP_LOCK);
/* set pdesc to point to the descriptor for *pblock
*/
pdesc = _BACKPTR(pblock);
if ( _ADDRESS(pdesc) != ((char *)pblock - _HDRSIZE) )
_heap_abort();
/* see if pblock is big enough already, or can be expanded (in place)
* to be big enough.
*/
if ( ((oldsize = currsize = BLKSZ(pdesc, pblock)) > newsize) ||
(_heap_expand_block(pdesc, &currsize, newsize) == 0) ) {
/* if necessary, mark pdesc as inuse
*/
if ( _IS_FREE(pdesc) ) {
_SET_INUSE(pdesc);
}
/* trim pdesc down to be exactly newsize bytes, if necessary
*/
if ( (currsize > newsize) &&
((pdesc2 = _heap_split_block(pdesc, newsize)) != NULL) )
{
_SET_FREE(pdesc2);
}
retp = pblock;
goto realloc_done;
}
/* try malloc-ing a new block of the requested size. if successful,
* copy over the data from the original block and free it.
*/
if ( (retp = _malloc_base(newsize)) != NULL ) {
memcpy(retp, pblock, oldsize);
_free_base_lk(pblock);
}
/* else if unsuccessful, return retp (== NULL) */
realloc_done:
/* if multi-thread support is enabled, unlock the heap here
*/
_munlock(_HEAP_LOCK);
return(retp);
}
/***
*void *_expand(void *pblock, size_t newsize) - expand/contract a block of memory
* in the heap
*
*Purpose:
* Resizes a block in the heap to newsize bytes. newsize may be either
* greater (expansion) or less (contraction) than the original size of
* the block. The block is NOT moved. In the case of expansion, if the
* block cannot be expanded to newsize bytes, it is expanded as much as
* possible.
*
* Special Notes For Multi-thread: The heap is locked just before pdesc
* is assigned and unlocked immediately prior to the return statement.
*
*Entry:
* void *pblock - pointer to block in the heap previously allocated
* by a call to malloc(), realloc() or _expand().
*
* size_t newsize - requested size for the resized block
*
*Exit:
* Success: Pointer to the resized memory block (i.e., pblock)
* Failure: NULL
*
*Uses:
*
*Exceptions:
* If pblock does not point to a valid allocation block in the heap,
* _expand() will behave unpredictably and probably corrupt the heap.
*
*******************************************************************************/
void * __cdecl _expand_base (
REG1 void *pblock,
size_t newsize
)
{
REG2 _PBLKDESC pdesc;
_PBLKDESC pdesc2;
void *retp;
size_t oldsize;
size_t currsize;
int index;
#if defined (_M_MPPC) || defined (_M_M68K)
struct _heap_region_ *pHeapRegions;
#endif /* defined (_M_MPPC) || defined (_M_M68K) */
/* make newsize a valid allocation block size (i.e., round up to the
* nearest whole number of dwords)
*/
newsize = _ROUND2(newsize, _GRANULARITY);
retp = pblock;
/* validate size */
if ( newsize > _HEAP_MAXREQ )
newsize = _HEAP_MAXREQ;
/* if multi-thread support enabled, lock the heap here
*/
_mlock(_HEAP_LOCK);
/* set pdesc to point to the descriptor for *pblock
*/
pdesc = _BACKPTR(pblock);
/* see if pblock is big enough already, or can be expanded (in place)
* to be big enough.
*/
if ( ((oldsize = currsize = BLKSZ(pdesc, pblock)) >= newsize) ||
(_heap_expand_block(pdesc, &currsize, newsize) == 0) ) {
/* pblock is (now) big enough. trim it down, if necessary
*/
if ( (currsize > newsize) &&
((pdesc2 = _heap_split_block(pdesc, newsize)) != NULL) )
{
_SET_FREE(pdesc2);
currsize = newsize;
}
goto expand_done;
}
/* if the heap block is at the end of a region, attempt to grow the
* region
*/
if ( (pdesc->pnextdesc == &_heap_desc.sentinel) ||
_IS_DUMMY(pdesc->pnextdesc) ) {
/* look up the region index
*/
#if defined (_M_MPPC) || defined (_M_M68K)
pHeapRegions = (struct _heap_region_ *)(*hHeapRegions);
for ( index = 0 ; index < _heap_region_table_cur ; index++ )
if (((pHeapRegions + index)->_regbase < pblock) &&
(((char *)((pHeapRegions + index)->_regbase) +
(pHeapRegions + index)->_currsize) >= (char *)pblock) )
break;
#else /* defined (_M_MPPC) || defined (_M_M68K) */
for ( index = 0 ; index < _HEAP_REGIONMAX ; index++ )
if ( (_heap_regions[index]._regbase < pblock) &&
(((char *)(_heap_regions[index]._regbase) +
_heap_regions[index]._currsize) >=
(char *)pblock) )
break;
#endif /* defined (_M_MPPC) || defined (_M_M68K) */
/* make sure a valid region index was obtained (pblock could
* lie in a portion of heap memory donated by a user call to
* _heapadd(), which therefore would not appear in the region
* table)
*/
#if defined (_M_MPPC) || defined (_M_M68K)
if ( index == _heap_region_table_cur ) {
#else /* defined (_M_MPPC) || defined (_M_M68K) */
if ( index == _HEAP_REGIONMAX ) {
#endif /* defined (_M_MPPC) || defined (_M_M68K) */
retp = NULL;
goto expand_done;
}
/* try growing the region. the difference between newsize and
* the current size of the block, rounded up to the nearest
* whole number of pages, is the amount the region needs to
* be grown. if successful, try expanding the block again
*/
if ( (_heap_grow_region(index, _ROUND2(newsize - currsize,
_PAGESIZE_)) == 0) &&
(_heap_expand_block(pdesc, &currsize, newsize) == 0) )
{
/* pblock is (now) big enough. trim it down to be
* exactly size bytes, if necessary
*/
if ( (currsize > newsize) && ((pdesc2 =
_heap_split_block(pdesc, newsize)) != NULL) )
{
_SET_FREE(pdesc2);
currsize = newsize;
}
}
else
retp = NULL;
}
else
retp = NULL;
expand_done:
/* if multi-thread support is enabled, unlock the heap here
*/
_munlock(_HEAP_LOCK);
return(retp);
}
/***
*int _heap_expand_block(pdesc, pcurrsize, newsize) - expand an allocation block
* in place (without trying to 'grow' the heap)
*
*Purpose:
*
*Entry:
* _PBLKDESC pdesc - pointer to the allocation block descriptor
* size_t *pcurrsize - pointer to size of the allocation block (i.e.,
* *pcurrsize == _BLKSIZE(pdesc), on entry)
* size_t newsize - requested minimum size for the expanded allocation
* block (i.e., newsize >= _BLKSIZE(pdesc), on exit)
*
*Exit:
* Success: 0
* Failure: -1
* In either case, *pcurrsize is updated with the new size of the block
*
*Exceptions:
* It is assumed that pdesc points to a valid allocation block descriptor.
* It is also assumed that _BLKSIZE(pdesc) == *pcurrsize on entry. If
* either of these assumptions is violated, _heap_expand_block will almost
* certainly trash the heap.
*
*******************************************************************************/
static int __cdecl _heap_expand_block (
REG1 _PBLKDESC pdesc,
REG3 size_t *pcurrsize,
size_t newsize
)
{
REG2 _PBLKDESC pdesc2;
_ASSERTE(("_heap_expand_block: bad pdesc arg", _CHECK_PDESC(pdesc)));
_ASSERTE(("_heap_expand_block: bad pcurrsize arg", *pcurrsize == _BLKSIZE(pdesc)));
for ( pdesc2 = pdesc->pnextdesc ; _IS_FREE(pdesc2) ;
pdesc2 = pdesc->pnextdesc ) {
/* coalesce with pdesc. check for special case of pdesc2
* being proverdesc.
*/
pdesc->pnextdesc = pdesc2->pnextdesc;
if ( pdesc2 == _heap_desc.proverdesc )
_heap_desc.proverdesc = pdesc;
/* update *pcurrsize, place *pdesc2 on the empty descriptor
* list and see if the coalesced block is now big enough
*/
*pcurrsize += _MEMSIZE(pdesc2);
_PUTEMPTY(pdesc2)
}
if ( *pcurrsize >= newsize )
return(0);
else
return(-1);
}
#endif /* WINHEAP */