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118 lines
4.5 KiB
C
118 lines
4.5 KiB
C
/*****************************************************************************/
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/* */
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/* realloc.c */
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/* */
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/* Change the size of an allocated memory block */
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/* */
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/* */
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/* */
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/* (C) 1998-2004 Ullrich von Bassewitz */
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/* Wacholderweg 14 */
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/* D-70597 Stuttgart */
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/* EMail: uz@musoftware.de */
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/* */
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/* */
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/* This software is provided 'as-is', without any expressed or implied */
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/* warranty. In no event will the authors be held liable for any damages */
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/* arising from the use of this software. */
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/* */
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/* Permission is granted to anyone to use this software for any purpose, */
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/* including commercial applications, and to alter it and redistribute it */
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/* freely, subject to the following restrictions: */
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/* */
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/* 1. The origin of this software must not be misrepresented; you must not */
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/* claim that you wrote the original software. If you use this software */
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/* in a product, an acknowledgment in the product documentation would be */
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/* appreciated but is not required. */
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/* 2. Altered source versions must be plainly marked as such, and must not */
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/* be misrepresented as being the original software. */
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/* 3. This notice may not be removed or altered from any source */
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/* distribution. */
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/* */
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/*****************************************************************************/
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#include <stdlib.h>
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#include <string.h>
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#include <_heap.h>
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void* __fastcall__ realloc (void* block, size_t size)
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{
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struct usedblock* b;
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struct usedblock* newblock;
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unsigned oldsize;
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unsigned newhptr;
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int diff;
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/* Check the block parameter */
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if (!block) {
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/* Block is NULL, same as malloc */
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return malloc (size);
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}
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/* Check the size parameter */
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if (size == 0) {
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/* Block is not NULL, but size is: free the block */
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free (block);
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return 0;
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}
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/* Make the internal used size from the given size */
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size += HEAP_ADMIN_SPACE;
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if (size < sizeof (struct freeblock)) {
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size = sizeof (struct freeblock);
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}
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/* The word below the user block contains a pointer to the start of the
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* raw memory block. The first word of this raw memory block is the full
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* size of the block. Get a pointer to the real block, get the old block
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* size.
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*/
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b = (((struct usedblock*) block) - 1)->start;
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oldsize = b->size;
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/* Get the size difference as a signed quantity */
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diff = size - oldsize;
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/* Is the block at the current heap top? */
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if (((unsigned) b) + oldsize == ((unsigned) _heapptr)) {
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/* Check if we've enough memory at the heap top */
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newhptr = ((unsigned) _heapptr) + diff;
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if (newhptr <= ((unsigned) _heapend)) {
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/* Ok, there's space enough */
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_heapptr = (unsigned*) newhptr;
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b->size = size;
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b->start = b;
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return block;
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}
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}
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/* The given block was not located on top of the heap, or there's no
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* room left. Try to allocate a new block and copy the data.
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*/
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if (newblock = malloc (size)) {
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/* Adjust the old size to the user visible portion */
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oldsize -= HEAP_ADMIN_SPACE;
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/* If the new block is larger than the old one, copy the old
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* data only
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*/
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if (size > oldsize) {
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size = oldsize;
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}
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/* Copy the block data */
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memcpy (newblock, block, size);
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free (block);
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}
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return newblock;
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}
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