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/*************************************************************************
* Copyright (C) 2014 Tavian Barnes <tavianator@tavianator.com> *
* *
* This file is part of The Dimension Library. *
* *
* The Dimension Library is free software; you can redistribute it and/ *
* or modify it under the terms of the GNU Lesser General Public License *
* as published by the Free Software Foundation; either version 3 of the *
* License, or (at your option) any later version. *
* *
* The Dimension Library is distributed in the hope that it will be *
* useful, but WITHOUT ANY WARRANTY; without even the implied warranty *
* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU *
* Lesser General Public License for more details. *
* *
* You should have received a copy of the GNU Lesser General Public *
* License along with this program. If not, see *
* <http://www.gnu.org/licenses/>. *
*************************************************************************/
/**
* @file
* Memory pool implementation.
*/
#include "dimension-internal.h"
#include <stdatomic.h>
/** A single allocation and associated destructor. */
typedef struct dmnsn_allocation {
void *ptr;
dmnsn_callback_fn *cleanup_fn;
} dmnsn_allocation;
/** Number of pointers per block, we want a block to fit in a single page. */
#define DMNSN_POOL_BLOCK_SIZE ((4096 - 4*sizeof(void *))/sizeof(dmnsn_allocation))
/** A single block in a thread pool. */
typedef struct dmnsn_pool_block {
/** Current index into allocs[]. */
size_t i;
/** All allocations in the current block. */
dmnsn_allocation allocs[DMNSN_POOL_BLOCK_SIZE];
/** Tail pointer to the previous block in the global chain. */
struct dmnsn_pool_block *prev;
} dmnsn_pool_block;
/** dmnsn_pool implementation. */
struct dmnsn_pool {
/** Thread-local block. */
pthread_key_t thread_block;
/** Global chain of pools. */
_Atomic(dmnsn_pool_block *) chain;
};
dmnsn_pool *
dmnsn_new_pool(void)
{
dmnsn_pool *pool = DMNSN_MALLOC(dmnsn_pool);
dmnsn_key_create(&pool->thread_block, NULL);
atomic_store_explicit(&pool->chain, NULL, memory_order_relaxed);
return pool;
}
void *
dmnsn_palloc(dmnsn_pool *pool, size_t size)
{
return dmnsn_palloc_tidy(pool, size, NULL);
}
void *
dmnsn_palloc_tidy(dmnsn_pool *pool, size_t size, dmnsn_callback_fn *cleanup_fn)
{
dmnsn_pool_block *old_block = pthread_getspecific(pool->thread_block);
dmnsn_pool_block *new_block = old_block;
if (dmnsn_unlikely(!old_block || old_block->i == DMNSN_POOL_BLOCK_SIZE)) {
new_block = DMNSN_MALLOC(dmnsn_pool_block);
new_block->i = 0;
}
dmnsn_allocation *alloc = new_block->allocs + new_block->i;
void *result = alloc->ptr = dmnsn_malloc(size);
alloc->cleanup_fn = cleanup_fn;
++new_block->i;
if (dmnsn_unlikely(new_block != old_block)) {
dmnsn_setspecific(pool->thread_block, new_block);
/* Atomically update pool->chain */
dmnsn_pool_block *chain;
do {
chain = atomic_load(&pool->chain);
} while (!atomic_compare_exchange_weak(&pool->chain, &chain, new_block));
new_block->prev = chain;
}
return result;
}
void
dmnsn_delete_pool(dmnsn_pool *pool)
{
if (!pool) {
return;
}
dmnsn_pool_block *block = atomic_load_explicit(&pool->chain, memory_order_relaxed);
while (block) {
/* Free all the allocations in reverse order */
for (size_t i = block->i; i-- > 0;) {
dmnsn_allocation *alloc = block->allocs + i;
if (alloc->cleanup_fn) {
alloc->cleanup_fn(alloc->ptr);
}
dmnsn_free(alloc->ptr);
}
/* Free the block itself and go to the previous one */
dmnsn_pool_block *saved = block;
block = block->prev;
dmnsn_free(saved);
}
dmnsn_key_delete(pool->thread_block);
dmnsn_free(pool);
}
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