1 files changed, 253 insertions, 0 deletions
diff --git a/src/libgit2/cache.c b/src/libgit2/cache.c
new file mode 100644
index 000000000..2f68e357c
--- /dev/null
+++ b/src/libgit2/cache.c
@@ -0,0 +1,253 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "cache.h"
+
+#include "repository.h"
+#include "commit.h"
+#include "thread.h"
+#include "util.h"
+#include "odb.h"
+#include "object.h"
+#include "git2/oid.h"
+
+bool git_cache__enabled = true;
+ssize_t git_cache__max_storage = (256 * 1024 * 1024);
+git_atomic_ssize git_cache__current_storage = {0};
+
+static size_t git_cache__max_object_size[8] = {
+	0,     /* GIT_OBJECT__EXT1 */
+	4096,  /* GIT_OBJECT_COMMIT */
+	4096,  /* GIT_OBJECT_TREE */
+	0,     /* GIT_OBJECT_BLOB */
+	4096,  /* GIT_OBJECT_TAG */
+	0,     /* GIT_OBJECT__EXT2 */
+	0,     /* GIT_OBJECT_OFS_DELTA */
+	0      /* GIT_OBJECT_REF_DELTA */
+};
+
+int git_cache_set_max_object_size(git_object_t type, size_t size)
+{
+	if (type < 0 || (size_t)type >= ARRAY_SIZE(git_cache__max_object_size)) {
+		git_error_set(GIT_ERROR_INVALID, "type out of range");
+		return -1;
+	}
+
+	git_cache__max_object_size[type] = size;
+	return 0;
+}
+
+int git_cache_init(git_cache *cache)
+{
+	memset(cache, 0, sizeof(*cache));
+
+	if ((git_oidmap_new(&cache->map)) < 0)
+		return -1;
+
+	if (git_rwlock_init(&cache->lock)) {
+		git_error_set(GIT_ERROR_OS, "failed to initialize cache rwlock");
+		return -1;
+	}
+
+	return 0;
+}
+
+/* called with lock */
+static void clear_cache(git_cache *cache)
+{
+	git_cached_obj *evict = NULL;
+
+	if (git_cache_size(cache) == 0)
+		return;
+
+	git_oidmap_foreach_value(cache->map, evict, {
+		git_cached_obj_decref(evict);
+	});
+
+	git_oidmap_clear(cache->map);
+	git_atomic_ssize_add(&git_cache__current_storage, -cache->used_memory);
+	cache->used_memory = 0;
+}
+
+void git_cache_clear(git_cache *cache)
+{
+	if (git_rwlock_wrlock(&cache->lock) < 0)
+		return;
+
+	clear_cache(cache);
+
+	git_rwlock_wrunlock(&cache->lock);
+}
+
+void git_cache_dispose(git_cache *cache)
+{
+	git_cache_clear(cache);
+	git_oidmap_free(cache->map);
+	git_rwlock_free(&cache->lock);
+	git__memzero(cache, sizeof(*cache));
+}
+
+/* Called with lock */
+static void cache_evict_entries(git_cache *cache)
+{
+	size_t evict_count = git_cache_size(cache) / 2048, i;
+	ssize_t evicted_memory = 0;
+
+	if (evict_count < 8)
+		evict_count = 8;
+
+	/* do not infinite loop if there's not enough entries to evict  */
+	if (evict_count > git_cache_size(cache)) {
+		clear_cache(cache);
+		return;
+	}
+
+	i = 0;
+	while (evict_count > 0) {
+		git_cached_obj *evict;
+		const git_oid *key;
+
+		if (git_oidmap_iterate((void **) &evict, cache->map, &i, &key) == GIT_ITEROVER)
+			break;
+
+		evict_count--;
+		evicted_memory += evict->size;
+		git_oidmap_delete(cache->map, key);
+		git_cached_obj_decref(evict);
+	}
+
+	cache->used_memory -= evicted_memory;
+	git_atomic_ssize_add(&git_cache__current_storage, -evicted_memory);
+}
+
+static bool cache_should_store(git_object_t object_type, size_t object_size)
+{
+	size_t max_size = git_cache__max_object_size[object_type];
+	return git_cache__enabled && object_size < max_size;
+}
+
+static void *cache_get(git_cache *cache, const git_oid *oid, unsigned int flags)
+{
+	git_cached_obj *entry;
+
+	if (!git_cache__enabled || git_rwlock_rdlock(&cache->lock) < 0)
+		return NULL;
+
+	if ((entry = git_oidmap_get(cache->map, oid)) != NULL) {
+		if (flags && entry->flags != flags) {
+			entry = NULL;
+		} else {
+			git_cached_obj_incref(entry);
+		}
+	}
+
+	git_rwlock_rdunlock(&cache->lock);
+
+	return entry;
+}
+
+static void *cache_store(git_cache *cache, git_cached_obj *entry)
+{
+	git_cached_obj *stored_entry;
+
+	git_cached_obj_incref(entry);
+
+	if (!git_cache__enabled && cache->used_memory > 0) {
+		git_cache_clear(cache);
+		return entry;
+	}
+
+	if (!cache_should_store(entry->type, entry->size))
+		return entry;
+
+	if (git_rwlock_wrlock(&cache->lock) < 0)
+		return entry;
+
+	/* soften the load on the cache */
+	if (git_atomic_ssize_get(&git_cache__current_storage) > git_cache__max_storage)
+		cache_evict_entries(cache);
+
+	/* not found */
+	if ((stored_entry = git_oidmap_get(cache->map, &entry->oid)) == NULL) {
+		if (git_oidmap_set(cache->map, &entry->oid, entry) == 0) {
+			git_cached_obj_incref(entry);
+			cache->used_memory += entry->size;
+			git_atomic_ssize_add(&git_cache__current_storage, (ssize_t)entry->size);
+		}
+	}
+	/* found */
+	else {
+		if (stored_entry->flags == entry->flags) {
+			git_cached_obj_decref(entry);
+			git_cached_obj_incref(stored_entry);
+			entry = stored_entry;
+		} else if (stored_entry->flags == GIT_CACHE_STORE_RAW &&
+			   entry->flags == GIT_CACHE_STORE_PARSED) {
+			if (git_oidmap_set(cache->map, &entry->oid, entry) == 0) {
+				git_cached_obj_decref(stored_entry);
+				git_cached_obj_incref(entry);
+			} else {
+				git_cached_obj_decref(entry);
+				git_cached_obj_incref(stored_entry);
+				entry = stored_entry;
+			}
+		} else {
+			/* NO OP */
+		}
+	}
+
+	git_rwlock_wrunlock(&cache->lock);
+	return entry;
+}
+
+void *git_cache_store_raw(git_cache *cache, git_odb_object *entry)
+{
+	entry->cached.flags = GIT_CACHE_STORE_RAW;
+	return cache_store(cache, (git_cached_obj *)entry);
+}
+
+void *git_cache_store_parsed(git_cache *cache, git_object *entry)
+{
+	entry->cached.flags = GIT_CACHE_STORE_PARSED;
+	return cache_store(cache, (git_cached_obj *)entry);
+}
+
+git_odb_object *git_cache_get_raw(git_cache *cache, const git_oid *oid)
+{
+	return cache_get(cache, oid, GIT_CACHE_STORE_RAW);
+}
+
+git_object *git_cache_get_parsed(git_cache *cache, const git_oid *oid)
+{
+	return cache_get(cache, oid, GIT_CACHE_STORE_PARSED);
+}
+
+void *git_cache_get_any(git_cache *cache, const git_oid *oid)
+{
+	return cache_get(cache, oid, GIT_CACHE_STORE_ANY);
+}
+
+void git_cached_obj_decref(void *_obj)
+{
+	git_cached_obj *obj = _obj;
+
+	if (git_atomic32_dec(&obj->refcount) == 0) {
+		switch (obj->flags) {
+		case GIT_CACHE_STORE_RAW:
+			git_odb_object__free(_obj);
+			break;
+
+		case GIT_CACHE_STORE_PARSED:
+			git_object__free(_obj);
+			break;
+
+		default:
+			git__free(_obj);
+			break;
+		}
+	}
+}