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109 lines
2.7 KiB
109 lines
2.7 KiB
/*
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* Yet Another Malloc
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* ya_freelist.c
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*/
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/* Block layout:
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*
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* -2 -1 0 size-4 size-3
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* +------+------+-------- - - - - - - - --------+------+------+
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* | prev | size | data... | size | next |
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* +------+------+-------- - - - - - - - --------+------+------+
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*
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*/
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/*----------*/
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/* Includes */
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/*----------*/
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#include <stdio.h>
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#include "ya_freelist.h"
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#include "ya_block.h"
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/*---------*/
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/* Globals */
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/*---------*/
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intptr_t *fl_start = NULL; // sorted increasing
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intptr_t *fl_end = NULL; // sorted decreasing
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/*-----------*/
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/* Functions */
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/*-----------*/
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#ifdef YA_DEBUG
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void fl_debug_print() {
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for (intptr_t *block = fl_start; block != NULL; block = fl_next(block)) {
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printf("Free block %p:%ld\n", block, block_size(block));
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}
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}
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#endif
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/* Splices the allocated block out of the free list. */
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void fl_alloc(intptr_t *block) {
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intptr_t size = block_size(block);
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intptr_t *prev = fl_prev(block);
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intptr_t *next = fl_next(block);
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fl_set_prev(block, NULL);
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fl_set_next(block, NULL);
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if (prev) {
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fl_set_next(prev, next);
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} else {
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fl_start = next;
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}
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if (next) {
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fl_set_prev(next, prev);
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} else {
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fl_end = prev;
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}
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}
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/* Adds the freed block to the appropriate in the free list, which is kept
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* in sorted increasing order. */
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void fl_free(intptr_t *block) {
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intptr_t *next;
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for (next = fl_start; next && block < next; next = fl_next(next)) {
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// *whistle*
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}
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if (next == fl_start) {
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// preprend block to the free list
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fl_set_prev(block, NULL);
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fl_set_next(block, fl_start);
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fl_set_prev(fl_start, block);
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fl_start = block;
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return;
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}
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if (!next) {
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// append block to the free list
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fl_set_prev(block, fl_end);
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fl_set_next(block, NULL);
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fl_set_next(fl_end, block);
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fl_end = block;
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return;
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}
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// splice the block in the middle of the list
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intptr_t *prev = fl_prev(next);
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fl_set_prev(block, prev);
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fl_set_next(block, next);
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fl_set_prev(next, block);
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fl_set_next(prev, block);
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}
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/* Returns the first block in the free list at min_size words long.
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* Returns NULL if no adequate block is found. Does not grow the heap. */
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intptr_t *fl_find(intptr_t min_size) {
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for (intptr_t *block = fl_start; block != NULL; block = fl_next(block)) {
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if (min_size <= block_size(block)) {
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return block;
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}
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}
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return NULL;
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}
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/* Force split of free block [block_size] into [size, block_size - size]. */
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void fl_split(intptr_t *block, intptr_t size) {
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fl_set_next(block, block+size);
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fl_set_prev(block+size, block);
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}
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