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#include "listpool.h"
#include <string.h>
void listpool_make_(listpool* pool, list* nodes, void* blocks,
size_t num_blocks, size_t block_size_bytes) {
assert(pool);
pool->block_size_bytes = block_size_bytes;
pool->num_blocks = num_blocks;
pool->free = &nodes[0];
pool->used = 0;
pool->nodes = nodes;
pool->blocks = blocks;
list_make(nodes, num_blocks);
memset(blocks, 0, num_blocks * block_size_bytes);
}
void* listpool_alloc_(listpool* pool) {
assert(pool);
if (!pool->free) {
return 0;
}
const size_t index = pool->free - pool->nodes;
assert(index < pool->num_blocks);
list* free = pool->free;
pool->free = pool->free->next;
// pool->used is always the head of the used list, so prepend the new item to
// the list.
list* new_used = free;
new_used->prev = 0;
new_used->next = pool->used;
if (pool->used) {
pool->used->prev = new_used;
}
pool->used = new_used;
return pool->blocks + index * pool->block_size_bytes;
}
void listpool_free_(listpool* pool, void** block_ptr) {
assert(pool);
assert(block_ptr);
memset(*block_ptr, 0, pool->block_size_bytes);
const size_t index =
((uint8_t*)*block_ptr - pool->blocks) / pool->block_size_bytes;
assert(index < pool->num_blocks);
list* item = &pool->nodes[index];
// We must remove the item from the used list first.
if (item->prev) {
item->prev->next = item->next;
}
if (item->next) {
item->next->prev = item->prev;
}
if (item == pool->used) {
pool->used = item->next;
}
// pool->free is always the head of the free list, so prepend the new item to
// the list. The item is now free to wire after removing it from the used
// list.
if (!pool->free) {
pool->free = item;
} else {
item->next = pool->free;
pool->free->prev = item;
pool->free = item;
}
*block_ptr = 0;
}
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