1 files changed, 123 insertions, 0 deletions
diff --git a/libdimension/pool.c b/libdimension/pool.c
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+++ b/libdimension/pool.c
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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"
+
+/** A single allocation and associated destructor. */
+typedef struct dmnsn_allocation {
+  void *ptr;
+  dmnsn_callback_fn *callback;
+} 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. */
+  dmnsn_pool_block *chain;
+  /** Mutex guarding the global chain. */
+  pthread_mutex_t mutex;
+};
+
+dmnsn_pool *
+dmnsn_new_pool(void)
+{
+  dmnsn_pool *pool = DMNSN_MALLOC(dmnsn_pool);
+  dmnsn_key_create(&pool->thread_block, NULL);
+  pool->chain = NULL;
+  dmnsn_initialize_mutex(&pool->mutex);
+  return pool;
+}
+
+void *
+dmnsn_pool_alloc(dmnsn_pool *pool, size_t size, dmnsn_callback_fn *callback)
+{
+  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->callback = callback;
+  ++new_block->i;
+
+  if (dmnsn_unlikely(new_block != old_block)) {
+    dmnsn_setspecific(pool->thread_block, new_block);
+
+    dmnsn_lock_mutex(&pool->mutex);
+      new_block->prev = pool->chain;
+      pool->chain = new_block;
+    dmnsn_unlock_mutex(&pool->mutex);
+  }
+
+  return result;
+}
+
+void
+dmnsn_delete_pool(dmnsn_pool *pool)
+{
+  if (!pool) {
+    return;
+  }
+
+  dmnsn_pool_block *block = pool->chain;
+  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->callback) {
+        alloc->callback(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_destroy_mutex(&pool->mutex);
+  dmnsn_key_delete(pool->thread_block);
+  dmnsn_free(pool);
+}