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85 lines
1.8 KiB
C
85 lines
1.8 KiB
C
/*
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* realloc.c
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*
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* Ullrich von Bassewitz, 06.06.1998
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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* realloc (void* block, size_t size)
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{
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unsigned* b;
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unsigned* newblock;
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unsigned oldsize;
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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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/* Get a pointer to the real block, get the old block size */
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b = (unsigned*) (((int) block) - 2);
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oldsize = *b;
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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 (((int) b) + oldsize == ((int) _hptr)) {
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/* Check if we've enough memory at the heap top */
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int newhptr;
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newhptr = ((int) _hptr) + diff;
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if (newhptr <= ((int) _hend)) {
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/* Ok, there's space enough */
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_hptr = (unsigned*) newhptr;
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*b = size;
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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 -= sizeof (unsigned);
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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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