1. 初始化
[[YYCache alloc] initWithName:@""];
- (instancetype) init {
NSLog(@"Use \"initWithName\" or \"initWithPath\" to create YYCache instance.");
return [self initWithPath:@""];
}
- (instancetype)initWithName:(NSString *)name {
if (name.length == 0) return nil;
NSString *cacheFolder = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
NSString *path = [cacheFolder stringByAppendingPathComponent:name];
return [self initWithPath:path];
}
- (instancetype)initWithPath:(NSString *)path {
if (path.length == 0) return nil;
YYDiskCache *diskCache = [[YYDiskCache alloc] initWithPath:path];
if (!diskCache) return nil;
NSString *name = [path lastPathComponent];
YYMemoryCache *memoryCache = [YYMemoryCache new];
memoryCache.name = name;
self = [super init];
_name = name;
_diskCache = diskCache;
_memoryCache = memoryCache;
return self;
}
+ (instancetype)cacheWithName:(NSString *)name {
return [[self alloc] initWithName:name];
}
+ (instancetype)cacheWithPath:(NSString *)path {
return [[self alloc] initWithPath:path];
}
- YYCache提供靜態(tài)方法和實(shí)例方法初始化钓辆，靜態(tài)方法本質(zhì)還是調(diào)用實(shí)例方法初始化缕溉。
- 實(shí)例方法提供name和path初始化考传，name會(huì)構(gòu)建路徑使用path方法進(jìn)行初始化
- 初始化時(shí)有YYMemoryCache和YYDiskCache。
- 使用name進(jìn)行初始化時(shí)证鸥，每個(gè)name對(duì)應(yīng)都會(huì)生成一個(gè)文件夾僚楞，數(shù)據(jù)庫(kù)。
2. YYMemoryCache內(nèi)存緩存
- (void)setObject:(id)object forKey:(id)key withCost:(NSUInteger)cost {
if (!key) return;
if (!object) {
[self removeObjectForKey:key];
return;
}
pthread_mutex_lock(&_lock);
_YYLinkedMapNode *node = CFDictionaryGetValue(_lru->_dic, (__bridge const void *)(key));
NSTimeInterval now = CACurrentMediaTime();
if (node) {
_lru->_totalCost -= node->_cost;
_lru->_totalCost += cost;
node->_cost = cost;
node->_time = now;
node->_value = object;
[_lru bringNodeToHead:node];
} else {
node = [_YYLinkedMapNode new];
node->_cost = cost;
node->_time = now;
node->_key = key;
node->_value = object;
[_lru insertNodeAtHead:node];
}
if (_lru->_totalCost > _costLimit) {
dispatch_async(_queue, ^{
[self trimToCost:_costLimit];
});
}
if (_lru->_totalCount > _countLimit) {
_YYLinkedMapNode *node = [_lru removeTailNode];
if (_lru->_releaseAsynchronously) {
dispatch_queue_t queue = _lru->_releaseOnMainThread ? dispatch_get_main_queue() : YYMemoryCacheGetReleaseQueue();
dispatch_async(queue, ^{
[node class]; //hold and release in queue
});
} else if (_lru->_releaseOnMainThread && !pthread_main_np()) {
dispatch_async(dispatch_get_main_queue(), ^{
[node class]; //hold and release in queue
});
}
}
pthread_mutex_unlock(&_lock);
}
從setObject:forKey:withCost看出YYMemoryCache的重要數(shù)據(jù)結(jié)構(gòu)_YYLinkedMap
2.1 _YYLinkedMap
@interface _YYLinkedMap : NSObject {
@package
CFMutableDictionaryRef _dic; // do not set object directly
NSUInteger _totalCost;
NSUInteger _totalCount;
_YYLinkedMapNode *_head; // MRU, do not change it directly
_YYLinkedMapNode *_tail; // LRU, do not change it directly
BOOL _releaseOnMainThread;
BOOL _releaseAsynchronously;
}
- (void)insertNodeAtHead:(_YYLinkedMapNode *)node{
...
}
- (void)bringNodeToHead:(_YYLinkedMapNode *)node{
...
}
_YYLinkedMap是一個(gè)雙向鏈接枉层。
insertNodeAtHead如果是新數(shù)據(jù)時(shí)泉褐，會(huì)把node插入在鏈表頭部
bringNodeToHead在設(shè)置緩存時(shí)，如果鏈表已經(jīng)包含node節(jié)點(diǎn)鸟蜡，會(huì)移動(dòng)節(jié)點(diǎn)到頭部兴枯。
CFMutableDictionaryRef _dic，存儲(chǔ)了key,model,方便快速查找矩欠。
2.2 setObject:forKey
- (void)setObject:(id)object forKey:(id)key {
[self setObject:object forKey:key withCost:0];
}
- (void)setObject:(id)object forKey:(id)key withCost:(NSUInteger)cost {
if (!key) return;
if (!object) {
[self removeObjectForKey:key];
return;
}
pthread_mutex_lock(&_lock);
_YYLinkedMapNode *node = CFDictionaryGetValue(_lru->_dic, (__bridge const void *)(key));
NSTimeInterval now = CACurrentMediaTime();
if (node) {
_lru->_totalCost -= node->_cost;
_lru->_totalCost += cost;
node->_cost = cost;
node->_time = now;
node->_value = object;
[_lru bringNodeToHead:node];
} else {
node = [_YYLinkedMapNode new];
node->_cost = cost;
node->_time = now;
node->_key = key;
node->_value = object;
[_lru insertNodeAtHead:node];
}
if (_lru->_totalCost > _costLimit) {
dispatch_async(_queue, ^{
[self trimToCost:_costLimit];
});
}
if (_lru->_totalCount > _countLimit) {
_YYLinkedMapNode *node = [_lru removeTailNode];
if (_lru->_releaseAsynchronously) {
dispatch_queue_t queue = _lru->_releaseOnMainThread ? dispatch_get_main_queue() : YYMemoryCacheGetReleaseQueue();
dispatch_async(queue, ^{
[node class]; //hold and release in queue
});
} else if (_lru->_releaseOnMainThread && !pthread_main_np()) {
dispatch_async(dispatch_get_main_queue(), ^{
[node class]; //hold and release in queue
});
}
}
pthread_mutex_unlock(&_lock);
}
- key不能為空财剖，為空直接return
- value不能為空，為空則需要移除對(duì)應(yīng)的key
- 獲取緩存中的node
- 如果node為空,生成一個(gè)node節(jié)點(diǎn)癌淮，insertNodeAtHead插入到鏈表頭部
- 如果node不為空,bringNodeToHead 修改時(shí)間并把node節(jié)點(diǎn)移動(dòng)到鏈表頭部
- 采用LRU算法躺坟，使用過(guò)即在最前面
- trimToCost:移除超出Cost的節(jié)點(diǎn)，removeTailNode移除掉超出count節(jié)點(diǎn)
2.3 _trimToCost
- (void)_trimToCost:(NSUInteger)costLimit {
BOOL finish = NO;
pthread_mutex_lock(&_lock);
if (costLimit == 0) {
[_lru removeAll];
finish = YES;
} else if (_lru->_totalCost <= costLimit) {
finish = YES;
}
pthread_mutex_unlock(&_lock);
if (finish) return;
NSMutableArray *holder = [NSMutableArray new];
while (!finish) {
if (pthread_mutex_trylock(&_lock) == 0) {
if (_lru->_totalCost > costLimit) {
_YYLinkedMapNode *node = [_lru removeTailNode];
if (node) [holder addObject:node];
} else {
finish = YES;
}
pthread_mutex_unlock(&_lock);
} else {
usleep(10 * 1000); //10 ms
}
}
if (holder.count) {
dispatch_queue_t queue = _lru->_releaseOnMainThread ? dispatch_get_main_queue() : YYMemoryCacheGetReleaseQueue();
dispatch_async(queue, ^{
[holder count]; // release in queue
});
}
}
- (instancetype)init {
self = super.init;
...
_countLimit = NSUIntegerMax;
_costLimit = NSUIntegerMax;
_ageLimit = DBL_MAX;
...
}
- costLimit = 0時(shí)乳蓄，標(biāo)識(shí)_costLimit已經(jīng)初始化咪橙；_lru->_totalCost <= costLimit 在正常范圍內(nèi)
- finish為NO,移除超出cost的節(jié)點(diǎn)；pthread_mutex_trylock判斷是否有其他線程鎖了，則10ms之后再試美侦；否則移除removeTailNode
- (_YYLinkedMapNode *)removeTailNode {
if (!_tail) return nil;
_YYLinkedMapNode *tail = _tail;
CFDictionaryRemoveValue(_dic, (__bridge const void *)(_tail->_key));
_totalCost -= _tail->_cost;
_totalCount--;
if (_head == _tail) {
_head = _tail = nil;
} else {
_tail = _tail->_prev;
_tail->_next = nil;
}
return tail;
}
- 移除_dic中的key,value
- 尾部指針指向尾部倒數(shù)第二個(gè)指針产舞，再把最后一個(gè)指針置nil
2.4 countLimit
if (_lru->_totalCount > _countLimit) {
_YYLinkedMapNode *node = [_lru removeTailNode];
if (_lru->_releaseAsynchronously) {
dispatch_queue_t queue = _lru->_releaseOnMainThread ? dispatch_get_main_queue() : YYMemoryCacheGetReleaseQueue();
dispatch_async(queue, ^{
[node class]; //hold and release in queue
});
} else if (_lru->_releaseOnMainThread && !pthread_main_np()) {
dispatch_async(dispatch_get_main_queue(), ^{
[node class]; //hold and release in queue
});
}
}
這一段只移除tailNode，而沒(méi)有循環(huán)判斷菠剩，countLimit是精確的易猫，每次增加或修改了countLimit.
2.5 objectForKey:
- (id)objectForKey:(id)key {
if (!key) return nil;
pthread_mutex_lock(&_lock);
_YYLinkedMapNode *node = CFDictionaryGetValue(_lru->_dic, (__bridge const void *)(key));
if (node) {
node->_time = CACurrentMediaTime();
[_lru bringNodeToHead:node];
}
pthread_mutex_unlock(&_lock);
return node ? node->_value : nil;
}
- 使用時(shí)從字典獲取node
- 如果node不為空，更新時(shí)間具壮，把節(jié)點(diǎn)移動(dòng)到頭部准颓。
符合LRU算法
2.6 內(nèi)存管理
- (instancetype)init {
self = super.init;
pthread_mutex_init(&_lock, NULL);
_lru = [_YYLinkedMap new];
_queue = dispatch_queue_create("com.ibireme.cache.memory", DISPATCH_QUEUE_SERIAL);
_countLimit = NSUIntegerMax;
_costLimit = NSUIntegerMax;
_ageLimit = DBL_MAX;
_autoTrimInterval = 5.0;
_shouldRemoveAllObjectsOnMemoryWarning = YES;
_shouldRemoveAllObjectsWhenEnteringBackground = YES;
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(_appDidReceiveMemoryWarningNotification) name:UIApplicationDidReceiveMemoryWarningNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(_appDidEnterBackgroundNotification) name:UIApplicationDidEnterBackgroundNotification object:nil];
[self _trimRecursively];
return self;
}
2.6.1 清空鏈表數(shù)據(jù)
收到內(nèi)存警告或進(jìn)入后臺(tái)時(shí)，清空緩存數(shù)據(jù)
2.6.2 _trimRecursively
每隔_autoTrimInterval時(shí)默認(rèn)5s棺妓，檢查Cost,Count,Age并清空過(guò)期數(shù)據(jù)
3. YYDiskCache持久化緩存
- (instancetype)initWithPath:(NSString *)path {
return [self initWithPath:path inlineThreshold:1024 * 20]; // 20KB
}
- (instancetype)initWithPath:(NSString *)path
inlineThreshold:(NSUInteger)threshold {
self = [super init];
if (!self) return nil;
YYDiskCache *globalCache = _YYDiskCacheGetGlobal(path);
if (globalCache) return globalCache;
YYKVStorageType type;
if (threshold == 0) {
type = YYKVStorageTypeFile;
} else if (threshold == NSUIntegerMax) {
type = YYKVStorageTypeSQLite;
} else {
type = YYKVStorageTypeMixed;
}
YYKVStorage *kv = [[YYKVStorage alloc] initWithPath:path type:type];
if (!kv) return nil;
_kv = kv;
_path = path;
_lock = dispatch_semaphore_create(1);
_queue = dispatch_queue_create("com.ibireme.cache.disk", DISPATCH_QUEUE_CONCURRENT);
_inlineThreshold = threshold;
_countLimit = NSUIntegerMax;
_costLimit = NSUIntegerMax;
_ageLimit = DBL_MAX;
_freeDiskSpaceLimit = 0;
_autoTrimInterval = 60;
[self _trimRecursively];
_YYDiskCacheSetGlobal(self);
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(_appWillBeTerminated) name:UIApplicationWillTerminateNotification object:nil];
return self;
}
- initWithPath默認(rèn)大小20kb
- 存儲(chǔ)的核心類是YYKVStorage,存儲(chǔ)分文件攘已、數(shù)據(jù)庫(kù)及混合存儲(chǔ)。
- YYKVStorage封裝了數(shù)據(jù)庫(kù)和文件的操作怜跑。
3.1 _trimRecursively
磁盤(pán)60s會(huì)檢查一次样勃，也可以手動(dòng)設(shè)置
- (void)_trimRecursively {
__weak typeof(self) _self = self;
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(_autoTrimInterval * NSEC_PER_SEC)), dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
__strong typeof(_self) self = _self;
if (!self) return;
[self _trimInBackground];
[self _trimRecursively];
});
}
- (void)_trimInBackground {
__weak typeof(self) _self = self;
dispatch_async(_queue, ^{
__strong typeof(_self) self = _self;
if (!self) return;
Lock();
[self _trimToCost:self.costLimit];
[self _trimToCount:self.countLimit];
[self _trimToAge:self.ageLimit];
[self _trimToFreeDiskSpace:self.freeDiskSpaceLimit];
Unlock();
});
}
3.2 setObject:forKey
- (void)setObject:(id<NSCoding>)object forKey:(NSString *)key {
if (!key) return;
if (!object) {
[self removeObjectForKey:key];
return;
}
NSData *extendedData = [YYDiskCache getExtendedDataFromObject:object];
NSData *value = nil;
if (_customArchiveBlock) {
value = _customArchiveBlock(object);
} else {
@try {
value = [NSKeyedArchiver archivedDataWithRootObject:object];//轉(zhuǎn)成NSData
}
@catch (NSException *exception) {
// nothing to do...
}
}
if (!value) return;
NSString *filename = nil;
if (_kv.type != YYKVStorageTypeSQLite) {
if (value.length > _inlineThreshold) {
filename = [self _filenameForKey:key];
}
}
Lock();
[_kv saveItemWithKey:key value:value filename:filename extendedData:extendedData];
Unlock();
}
- _customArchiveBlock自定義block,如果沒(méi)有則使用系統(tǒng)方法object轉(zhuǎn)data
- saveItemWithKey保存key,value
- (BOOL)saveItemWithKey:(NSString *)key value:(NSData *)value filename:(NSString *)filename extendedData:(NSData *)extendedData {
if (key.length == 0 || value.length == 0) return NO;
if (_type == YYKVStorageTypeFile && filename.length == 0) {
return NO;
}
if (filename.length) {
if (![self _fileWriteWithName:filename data:value]) {
return NO;
}
if (![self _dbSaveWithKey:key value:value fileName:filename extendedData:extendedData]) {
[self _fileDeleteWithName:filename];
return NO;
}
return YES;
} else {
if (_type != YYKVStorageTypeSQLite) {
NSString *filename = [self _dbGetFilenameWithKey:key];
if (filename) {
[self _fileDeleteWithName:filename];
}
}
return [self _dbSaveWithKey:key value:value fileName:nil extendedData:extendedData];
}
}
- filename不為空時(shí)，_fileWriteWithName寫(xiě)入文件
- _dbSaveWithKey保存到數(shù)據(jù)庫(kù)
3.3 objectForKey:
- (id<NSCoding>)objectForKey:(NSString *)key {
if (!key) return nil;
Lock();
YYKVStorageItem *item = [_kv getItemForKey:key];
Unlock();
if (!item.value) return nil;
id object = nil;
if (_customUnarchiveBlock) {
object = _customUnarchiveBlock(item.value);
} else {
@try {
object = [NSKeyedUnarchiver unarchiveObjectWithData:item.value];//data轉(zhuǎn)成對(duì)象
}
@catch (NSException *exception) {
// nothing to do...
}
}
if (object && item.extendedData) {
[YYDiskCache setExtendedData:item.extendedData toObject:object];
}
return object;
}
- (YYKVStorageItem *)getItemForKey:(NSString *)key {
if (key.length == 0) return nil;
YYKVStorageItem *item = [self _dbGetItemWithKey:key excludeInlineData:NO];
if (item) {
[self _dbUpdateAccessTimeWithKey:key];//使用后需要更新時(shí)間
if (item.filename) {
item.value = [self _fileReadWithName:item.filename];
if (!item.value) {
[self _dbDeleteItemWithKey:key];
item = nil;
}
}
}
return item;
}
總結(jié):
- YYCache很好的支持了對(duì)象的持久化問(wèn)題性芬，采用文件與數(shù)據(jù)庫(kù)結(jié)合的方式進(jìn)行存儲(chǔ)彤灶。
- 同時(shí)對(duì)象存儲(chǔ)采用序列化的方式，解決了不同對(duì)象差異的存儲(chǔ)問(wèn)題批旺。
- 內(nèi)存采用雙鏈表實(shí)現(xiàn)LRU算法，磁盤(pán)存儲(chǔ)采用最后更新時(shí)間的方式來(lái)實(shí)現(xiàn)LRU算法诵姜。
這里我有個(gè)小疑問(wèn):磁盤(pán)采用60s的方式進(jìn)行輪詢清理汽煮，每個(gè)YYCache對(duì)象都有60s,當(dāng)有多個(gè)YYCache對(duì)象使用時(shí)，是否需要考慮下60s的長(zhǎng)度問(wèn)題棚唆。
