text: /*
   * 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-utils.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_OBJ__EXT1 */
  	4096,  /* GIT_OBJ_COMMIT */
  	4096,  /* GIT_OBJ_TREE */
  	0,     /* GIT_OBJ_BLOB */
  	4096,  /* GIT_OBJ_TAG */
  	0,     /* GIT_OBJ__EXT2 */
  	0,     /* GIT_OBJ_OFS_DELTA */
  	0      /* GIT_OBJ_REF_DELTA */
  };
  
  int git_cache_set_max_object_size(git_otype type, size_t size)
  {
  	if (type < 0 || (size_t)type >= ARRAY_SIZE(git_cache__max_object_size)) {
  		giterr_set(GITERR_INVALID, "type out of range");
  		return -1;
  	}
  
  	git_cache__max_object_size[type] = size;
  	return 0;
  }
  
  void git_cache_dump_stats(git_cache *cache)
  {
  	git_cached_obj *object;
  
  	if (git_cache_size(cache) == 0)
  		return;
  
  	printf("Cache %p: %"PRIuZ" items cached, %"PRIdZ" bytes\n",
  		cache, git_cache_size(cache), cache->used_memory);
  
  	git_oidmap_foreach_value(cache->map, object, {
  		char oid_str[9];
  		printf(" %s%c %s (%"PRIuZ")\n",
  			git_object_type2string(object->type),
  			object->flags == GIT_CACHE_STORE_PARSED ? '*' : ' ',
  			git_oid_tostr(oid_str, sizeof(oid_str), &object->oid),
  			object->size
  		);
  	});
  }
  
  int git_cache_init(git_cache *cache)
  {
  	memset(cache, 0, sizeof(*cache));
  	cache->map = git_oidmap_alloc();
  	GITERR_CHECK_ALLOC(cache->map);
  	if (git_rwlock_init(&cache->lock)) {
  		giterr_set(GITERR_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_free(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)
  {
  	uint32_t seed = rand();
  	size_t evict_count = 8;
  	ssize_t evicted_memory = 0;
  
  	/* do not infinite loop if there's not enough entries to evict  */
  	if (evict_count > git_cache_size(cache)) {
  		clear_cache(cache);
  		return;
  	}
  
  	while (evict_count > 0) {
  		khiter_t pos = seed++ % git_oidmap_end(cache->map);
  
  		if (git_oidmap_has_data(cache->map, pos)) {
  			git_cached_obj *evict = git_oidmap_value_at(cache->map, pos);
  
  			evict_count--;
  			evicted_memory += evict->size;
  			git_cached_obj_decref(evict);
  
  			git_oidmap_delete_at(cache->map, pos);
  		}
  	}
  
  	cache->used_memory -= evicted_memory;
  	git_atomic_ssize_add(&git_cache__current_storage, -evicted_memory);
  }
  
  static bool cache_should_store(git_otype 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)
  {
  	khiter_t pos;
  	git_cached_obj *entry = NULL;
  
  	if (!git_cache__enabled || git_rwlock_rdlock(&cache->lock) < 0)
  		return NULL;
  
  	pos = git_oidmap_lookup_index(cache->map, oid);
  	if (git_oidmap_valid_index(cache->map, pos)) {
  		entry = git_oidmap_value_at(cache->map, pos);
  
  		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)
  {
  	khiter_t pos;
  
  	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_cache__current_storage.val > git_cache__max_storage)
  		cache_evict_entries(cache);
  
  	pos = git_oidmap_lookup_index(cache->map, &entry->oid);
  
  	/* not found */
  	if (!git_oidmap_valid_index(cache->map, pos)) {
  		int rval;
  
  		git_oidmap_insert(cache->map, &entry->oid, entry, &rval);
  		if (rval >= 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 {
  		git_cached_obj *stored_entry = git_oidmap_value_at(cache->map, pos);
  
  		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) {
  			git_cached_obj_decref(stored_entry);
  			git_cached_obj_incref(entry);
  
  			git_oidmap_set_key_at(cache->map, pos, &entry->oid);
  			git_oidmap_set_value_at(cache->map, pos, 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_atomic_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;
  		}
  	}
  }
  