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The old hash table with chained buckets has been replaced by a new one using Cuckoo hashing, which offers guaranteed constant lookup times. This should improve speeds on most use cases, since hash tables in libgit2 are usually used as caches where the objects are stored once and queried several times. The Cuckoo hash implementation is based off the one in the Basekit library [1] for the IO language, but rewritten to support an arbritrary number of hashes. We currently use 3 to maximize the usage of the nodes pool. [1]: https://github.com/stevedekorte/basekit/blob/master/source/CHash.c Signed-off-by: Vicent Marti <tanoku@gmail.com>
198 lines
5.0 KiB
C
198 lines
5.0 KiB
C
/*
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* This file is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License, version 2,
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* as published by the Free Software Foundation.
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*
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* In addition to the permissions in the GNU General Public License,
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* the authors give you unlimited permission to link the compiled
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* version of this file into combinations with other programs,
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* and to distribute those combinations without any restriction
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* coming from the use of this file. (The General Public License
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* restrictions do apply in other respects; for example, they cover
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* modification of the file, and distribution when not linked into
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* a combined executable.)
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*
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* This file is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; see the file COPYING. If not, write to
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* the Free Software Foundation, 51 Franklin Street, Fifth Floor,
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* Boston, MA 02110-1301, USA.
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*/
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#include "test_lib.h"
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#include "test_helpers.h"
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#include "hashtable.h"
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#include "hash.h"
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typedef struct _aux_object {
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int __bulk;
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git_oid id;
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int visited;
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} table_item;
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uint32_t hash_func(const void *key, int hash_id)
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{
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uint32_t r;
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git_oid *id;
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id = (git_oid *)key;
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memcpy(&r, id->id + (hash_id * sizeof(uint32_t)), sizeof(r));
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return r;
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}
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int hash_cmpkey(const void *a, const void *b)
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{
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return git_oid_cmp(a, b);
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}
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BEGIN_TEST("table", table_create)
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git_hashtable *table = NULL;
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table = git_hashtable_alloc(55, hash_func, hash_cmpkey);
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must_be_true(table != NULL);
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must_be_true(table->size_mask + 1 == 64);
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git_hashtable_free(table);
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END_TEST
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BEGIN_TEST("table", table_populate)
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const int objects_n = 32;
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int i;
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table_item *objects;
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git_hashtable *table = NULL;
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table = git_hashtable_alloc(objects_n * 2, hash_func, hash_cmpkey);
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must_be_true(table != NULL);
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objects = git__malloc(objects_n * sizeof(table_item));
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memset(objects, 0x0, objects_n * sizeof(table_item));
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/* populate the hash table */
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for (i = 0; i < objects_n; ++i) {
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git_hash_buf(&(objects[i].id), &i, sizeof(int));
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must_pass(git_hashtable_insert(table, &(objects[i].id), &(objects[i])));
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}
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/* make sure all the inserted objects can be found */
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for (i = 0; i < objects_n; ++i) {
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git_oid id;
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table_item *ob;
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git_hash_buf(&id, &i, sizeof(int));
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ob = (table_item *)git_hashtable_lookup(table, &id);
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must_be_true(ob != NULL);
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must_be_true(ob == &(objects[i]));
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}
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/* make sure we cannot find inexisting objects */
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for (i = 0; i < 50; ++i) {
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int hash_id;
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git_oid id;
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hash_id = (rand() % 50000) + objects_n;
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git_hash_buf(&id, &hash_id, sizeof(int));
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must_be_true(git_hashtable_lookup(table, &id) == NULL);
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}
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git_hashtable_free(table);
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free(objects);
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END_TEST
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BEGIN_TEST("table", table_resize)
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const int objects_n = 64;
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int i;
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unsigned int old_size;
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table_item *objects;
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git_hashtable *table = NULL;
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table = git_hashtable_alloc(objects_n, hash_func, hash_cmpkey);
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must_be_true(table != NULL);
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objects = git__malloc(objects_n * sizeof(table_item));
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memset(objects, 0x0, objects_n * sizeof(table_item));
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old_size = table->size_mask + 1;
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/* populate the hash table -- should be automatically resized */
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for (i = 0; i < objects_n; ++i) {
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git_hash_buf(&(objects[i].id), &i, sizeof(int));
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must_pass(git_hashtable_insert(table, &(objects[i].id), &(objects[i])));
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}
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must_be_true(table->size_mask > old_size);
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/* make sure all the inserted objects can be found */
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for (i = 0; i < objects_n; ++i) {
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git_oid id;
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table_item *ob;
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git_hash_buf(&id, &i, sizeof(int));
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ob = (table_item *)git_hashtable_lookup(table, &id);
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must_be_true(ob != NULL);
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must_be_true(ob == &(objects[i]));
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}
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git_hashtable_free(table);
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free(objects);
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END_TEST
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BEGIN_TEST("tableit", table_iterator)
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const int objects_n = 32;
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int i;
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table_item *objects, *ob;
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const void *_unused;
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git_hashtable *table = NULL;
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table = git_hashtable_alloc(objects_n * 2, hash_func, hash_cmpkey);
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must_be_true(table != NULL);
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objects = git__malloc(objects_n * sizeof(table_item));
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memset(objects, 0x0, objects_n * sizeof(table_item));
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/* populate the hash table */
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for (i = 0; i < objects_n; ++i) {
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git_hash_buf(&(objects[i].id), &i, sizeof(int));
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must_pass(git_hashtable_insert(table, &(objects[i].id), &(objects[i])));
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}
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GIT_HASHTABLE_FOREACH(table, _unused, ob,
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ob->visited = 1;
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);
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/* make sure all nodes have been visited */
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for (i = 0; i < objects_n; ++i)
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must_be_true(objects[i].visited);
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git_hashtable_free(table);
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free(objects);
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END_TEST
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git_testsuite *libgit2_suite_hashtable(void)
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{
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git_testsuite *suite = git_testsuite_new("Hashtable");
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ADD_TEST(suite, "table", table_create);
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ADD_TEST(suite, "table", table_populate);
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ADD_TEST(suite, "table", table_resize);
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ADD_TEST(suite, "tableit", table_iterator);
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return suite;
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}
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