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#include "heap.basic.h"
#include "paging.h"
#include <lib/mutex.h>
#include <core/sys.h>
void heap_create(struct heap *heap, size_t start, size_t datasize, size_t maxdatasize) {
uint32_t i;
if (start & 0x0FFF) start = (start & 0xFFFFF000) + 0x1000;
// Allocate frames
for (i = start; i < start + datasize; i += 0x1000) {
page_map(pagedir_getPage(kernel_pagedir, i, 1), frame_alloc(), 0, 0);
}
heap->start_addr = start;
heap->end_addr = start + datasize;
heap->max_end = start + maxdatasize;
struct heap_header *first = (struct heap_header*)start;
first->magic = HH_FREE_MAGIC;
first->prev = first->next = first;
heap->first = first;
heap->first_free = first;
heap->mutex = 0;
}
// ***** UTILITY FUNCTIONS *****
#define BLK_SIZE(blk) (blk->next == blk ? ((size_t)heap->end_addr - (size_t)blk) : ((size_t)blk->next - (size_t)blk))
#define BLK_FREE(blk) (blk->magic == HH_FREE_MAGIC)
void blk_split(struct heap *heap, struct heap_header *hdr, size_t size) {
ASSERT (size >= MIN_BLK_SIZE);
ASSERT (BLK_SIZE(hdr) > size);
ASSERT (BLK_SIZE(hdr) - size >= MIN_BLK_SIZE);
ASSERT (BLK_FREE(hdr));
struct heap_header *hdr_nxt = (struct heap_header*)((size_t)hdr + size);
hdr_nxt->magic = HH_FREE_MAGIC;
hdr_nxt->prev = hdr;
if (hdr->next == hdr) {
hdr_nxt->next = hdr_nxt;
} else {
hdr_nxt->next = hdr->next;
hdr->next->prev = hdr_nxt;
}
hdr->next = hdr_nxt;
}
void blk_combine_next(struct heap *heap, struct heap_header *hdr) {
ASSERT (hdr != hdr->next); // make sure we are not the last block
ASSERT (hdr->magic == HH_FREE_MAGIC);
ASSERT (hdr->next->magic == HH_FREE_MAGIC);
struct heap_header *hdr_nxt = hdr->next;
if (hdr_nxt->next == hdr_nxt) {
hdr->next = hdr;
} else {
hdr->next = hdr_nxt->next;
hdr_nxt->next->prev = hdr;
}
}
// ***** Allocation/Freeing functions *****
void *heap_alloc(struct heap *heap, size_t sz) {
/* Algorithm :
1 Use heap->first_free to find first effectively free block, update heap->first_free
2 Find first free AND BIG ENOUGH block
- If no block can be found, return 0 (no heap expand yet)
3 If that block is too big, split it in two
4 Mark that block as used and return it's address + sizeof(heap_header) */
mutex_lock(&heap->mutex);
sz += sizeof(struct heap_header);
if (sz < MIN_BLK_SIZE) sz = MIN_BLK_SIZE;
if (sz % 4 != 0) sz = sz + 4 - (sz % 4);
// 1
struct heap_header *it = heap->first_free;
while (!BLK_FREE(it) && it != it->next) it = it->next;
if (!BLK_FREE(it) && it == it->next) {
mutex_unlock(&heap->mutex);
return 0;
}
heap->first_free = it;
// 2
while (BLK_SIZE(it) < sz && it != it->next) it = it->next;
if (BLK_SIZE(it) < sz) { // no block could be found
mutex_unlock(&heap->mutex);
return 0;
}
// 3
if (BLK_SIZE(it) >= sz + MIN_BLK_SIZE) blk_split(heap, it, sz);
// 4
void *ret = (void*)((size_t)it + sizeof(struct heap_header));
it->magic = HH_ALLOC_MAGIC;
mutex_unlock(&heap->mutex);
return ret;
}
void heap_free(struct heap *heap, void *ptr) {
/* Algorithm :
1 Get block pointer to the block we are freeing
2 Mark that block as free
3 If block->next is free, combine_next(block)
4 If block->prev is free, block = block->prev; combine_next(block)
5 If block < heap->first_free; heap->first_free = block
*/
mutex_lock(&heap->mutex);
// 1
struct heap_header *hdr = (struct heap_header*)((size_t)ptr - sizeof(struct heap_header));
if (hdr->magic != HH_ALLOC_MAGIC) return;
// 2
hdr->magic = HH_FREE_MAGIC;
// 3
if (hdr->next != hdr && hdr->next->magic == HH_FREE_MAGIC) blk_combine_next(heap, hdr);
// 4
if (hdr->prev != hdr && hdr->prev->magic == HH_FREE_MAGIC) {
hdr = hdr->prev;
blk_combine_next(heap, hdr);
}
// 5
if (hdr < heap->first_free) heap->first_free = hdr;
mutex_unlock(&heap->mutex);
}
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