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/***
*expand.c - Win32 expand heap routine
*
* Copyright (c) 1991-1992, Microsoft Corporation. All rights reserved.
*
*Purpose:
*
*Revision History:
* 01-15-92 JCR Module created.
* 02-04-92 GJF Replaced windows.h with oscalls.h.
* 05-06-92 DJM ifndef out of POSIX build.
* 09-23-92 SRW Change winheap code to call NT directly always
* 10-15-92 SKS Removed the ill-named HEAP_GROWTH_ALLOWED flag
* which was causing a bug: _expand was behaving like
* realloc(), by moving the block when it could not be
* grown in place. _expand() must NEVER move the block.
* Also added a safety check to work around a bug in
* HeapReAlloc, where it returns success even
* when it fails to grow the block in place.
* 10-28-92 SRW Change winheap code to call Heap????Ex calls
* 11-05-92 SKS Change name of variable "CrtHeap" to "_crtheap"
* 11-07-92 SRW _NTIDW340 replaced by linkopts\betacmp.c
* 11-16-92 SRW Heap???Ex functions renamed to Heap???
*
*******************************************************************************/
#ifndef _POSIX_
#include <cruntime.h>
#include <malloc.h>
#include <winheap.h>
#include <oscalls.h>
/***
*void *_expand(void *pblck, 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.
*
* NOTES:
*
* (1) In this implementation, if the block cannot be grown to the
* desired size, the resulting block will NOT be grown to the max
* possible size. (That is, either it works or it doesn't.)
*
* (2) Unlike other implementations, you can NOT pass a previously
* freed block to this routine and expect it to work.
*
*Entry:
* void *pblck - 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., pblck)
* Failure: NULL
*
*Uses:
*
*Exceptions:
* If pblck does not point to a valid allocation block in the heap,
* _expand() will behave unpredictably and probably corrupt the heap.
*
*******************************************************************************/
void * _CALLTYPE1 _expand(pblock, n)
void * pblock;
size_t n;
{
void * p;
p = HeapReAlloc(_crtheap,
HEAP_REALLOC_IN_PLACE_ONLY,
pblock,
n ? n : 1
);
/**
* Temporary BUG work-around:
* HeapReAlloc sometimes (often?) returns success
* even when there has been a failure to grow in place.
* This conditional will recognize this case and handle it.
**/
return ( p == pblock ) && ( _msize(pblock) >= n ) ? pblock : NULL;
}
#endif /* !_POSIX_ */
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