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/*
* This file is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License, version 2,
* as published by the Free Software Foundation.
*
* In addition to the permissions in the GNU General Public License,
* the authors give you unlimited permission to link the compiled
* version of this file into combinations with other programs,
* and to distribute those combinations without any restriction
* coming from the use of this file. (The General Public License
* restrictions do apply in other respects; for example, they cover
* modification of the file, and distribution when not linked into
* a combined executable.)
*
* This file 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
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
#include "common.h"
#include "repository.h"
#include "commit.h"
#include "thread-utils.h"
#include "cache.h"
#define GIT_CACHE_OPENADR 3
GIT_INLINE(int) cached_obj_compare(git_cached_obj *obj, const git_oid *oid)
{
return git_oid_cmp(&obj->oid, oid);
}
GIT_INLINE(void) cached_obj_incref(git_cached_obj *obj)
{
git_atomic_inc(&obj->refcount);
}
GIT_INLINE(void) cached_obj_decref(git_cached_obj *obj, git_cached_obj_freeptr free_obj)
{
if (git_atomic_dec(&obj->refcount) == 0)
free_obj(obj);
}
void git_cache_init(git_cache *cache, size_t size, git_cached_obj_freeptr free_ptr)
{
size_t i;
if (size < 8)
size = 8;
/* round up size to closest power of 2 */
size--;
size |= size >> 1;
size |= size >> 2;
size |= size >> 4;
size |= size >> 8;
size |= size >> 16;
cache->size_mask = size;
cache->lru_count = 0;
cache->free_obj = free_ptr;
cache->nodes = git__malloc((size + 1) * sizeof(cache_node));
for (i = 0; i < (size + 1); ++i) {
git_mutex_init(&cache->nodes[i].lock);
cache->nodes[i].ptr = NULL;
cache->nodes[i].lru = 0;
}
}
void git_cache_free(git_cache *cache)
{
size_t i;
for (i = 0; i < (cache->size_mask + 1); ++i) {
cached_obj_decref(cache->nodes[i].ptr, cache->free_obj);
git_mutex_free(&cache->nodes[i].lock);
}
free(cache->nodes);
}
void *git_cache_get(git_cache *cache, const git_oid *oid)
{
const uint32_t *hash;
size_t i, pos, found = 0;
cache_node *node;
hash = (const uint32_t *)oid->id;
for (i = 0; !found && i < GIT_CACHE_OPENADR; ++i) {
pos = hash[i] & cache->size_mask;
node = &cache->nodes[pos];
git_mutex_lock(&node->lock);
{
if (cached_obj_compare(node->ptr, oid) == 0) {
cached_obj_incref(node->ptr);
node->lru = ++cache->lru_count;
found = 1;
}
}
git_mutex_unlock(&node->lock);
}
return found ? node->ptr : NULL;
}
void *git_cache_try_store(git_cache *cache, void *entry)
{
cache_node *nodes[GIT_CACHE_OPENADR], *lru_node;
const uint32_t *hash;
const git_oid *oid;
size_t i, stored = 0;
oid = &((git_cached_obj*)entry)->oid;
hash = (const uint32_t *)oid->id;
/* increase the refcount on this object, because
* the cache now owns it */
cached_obj_incref(entry);
for (i = 0; i < GIT_CACHE_OPENADR; ++i) {
size_t pos = hash[i] & cache->size_mask;
nodes[i] = &cache->nodes[pos];
git_mutex_lock(&nodes[i]->lock);
}
lru_node = nodes[0];
for (i = 0; !stored && entry && i < GIT_CACHE_OPENADR; ++i) {
if (nodes[i]->ptr == NULL) {
nodes[i]->ptr = entry;
nodes[i]->lru = ++cache->lru_count;
stored = 1;
} else if (cached_obj_compare(nodes[i]->ptr, oid) == 0) {
cached_obj_decref(entry, cache->free_obj);
entry = nodes[i]->ptr;
stored = 1;
}
if (nodes[i]->lru < lru_node->lru)
lru_node = nodes[i];
}
if (!stored) {
void *old_entry = lru_node->ptr;
assert(old_entry);
cached_obj_decref(old_entry, cache->free_obj);
lru_node->ptr = entry;
lru_node->lru = ++cache->lru_count;
}
/* increase the refcount again, because we are
* returning it to the user */
cached_obj_incref(entry);
for (i = 0; i < GIT_CACHE_OPENADR; ++i)
git_mutex_unlock(&nodes[i]->lock);
return entry;
}
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