Merge branch 'master' of https://github.com/rs/SDWebImage into 5.x

* 'master' of https://github.com/rs/SDWebImage:
  Bumped version to 4.3.1
  update CHANGELOG
  Create a subclass of NSCache using a weak cache. Only remove the cache when memory warning and sync back the alive instance from weak cache into cache.

# Conflicts:
#	SDWebImage/SDImageCache.m

CHANGELOG.md

@@ -1,3 +1,29 @@
+## [4.3.1 - 4.3.0 Patch](https://github.com/rs/SDWebImage/releases/tag/4.3.1)
+See [all tickets marked for the 4.3.1 release](https://github.com/rs/SDWebImage/milestone/22)
+
+#### Fixes
+- Cache
+	- Fix that SDImageCacheQueryDataWhenInMemory should response cacheType to memory cache when the in-memory cache hit #2218
+- Project
+	- Fix the macOS wrong minimum deployment target version to 10.9 #2206
+
+#### Performances
+- Download Operation
+	- Decode the image in the operation level's queue instead of URLSession delegate queue #2199
+
+#### Improvements
+- Coder
+	- Create a subclass of NSBitmapImageRep to fix the GIF frame duration issue on macOS #2223 
+- View Category
+	- Expose the read write to FLAnimatedImage associate to the UIImage to allow advanced feature like placeholder #2220
+- Cache
+	- Create a subclass of NSCache using a weak cache #2228
+- Download Operation
+	- Improvement download operation for priority and some protect #2208
+- Project
+	- Fix CLANG\_WARN\_OBJC\_IMPLICIT\_RETAIN\_SELF warning #2225 
+
+
 ## [4.3.0 - Image Progress & Transition, on Jan 31th, 2018](https://github.com/rs/SDWebImage/releases/tag/4.3.0)
 See [all tickets marked for the 4.3.0 release](https://github.com/rs/SDWebImage/milestone/21)
 
@@ -20,7 +46,7 @@ See [all tickets marked for the 4.3.0 release](https://github.com/rs/SDWebImage/
 - Cache
 	- Fix the getSize method which use the default file manager instead of current file manager #2180
 - Manager
-	- Fix the leak of runningOperations in race condition #2177 (Manager)
+	- Fix the leak of runningOperations on race condition #2177
 - Downloader
 	- Ensure all the session delegate completionHandler called and fix the leak when response error code below iOS 10 #2197
 	- Fix dispatch_sync blocking the main queue on race condition #2184
@@ -31,9 +57,9 @@ See [all tickets marked for the 4.3.0 release](https://github.com/rs/SDWebImage/
 - Prefetcher
 	- Fix the issue that prefetcher will cause stack overflow when the input urls list is huge because of recursion function call #2196
 
-#### Performance
+#### Performances
 - View Category
-	- Use the associate object to store the FLAnimatedImage into memory cache, avoid blinking or UIView transaction #2181
+	- Use the associate object to store the FLAnimatedImage into memory cache, avoid blinking or UIView transition #2181
 
 #### Improvements
 - Cache

SDWebImage.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name = 'SDWebImage'
-  s.version = '4.3.0'
+  s.version = '4.3.1'
 
   s.osx.deployment_target = '10.10'
   s.ios.deployment_target = '8.0'

SDWebImage/SDImageCache.m

@@ -11,6 +11,9 @@
 #import "NSImage+Additions.h"
 #import "SDWebImageCodersManager.h"
 
+#define LOCK(lock) dispatch_semaphore_wait(lock, DISPATCH_TIME_FOREVER);
+#define UNLOCK(lock) dispatch_semaphore_signal(lock);
+
 static void * SDImageCacheContext = &SDImageCacheContext;
 
 FOUNDATION_STATIC_INLINE NSUInteger SDCacheCostForImage(UIImage *image) {
@@ -21,10 +24,106 @@ FOUNDATION_STATIC_INLINE NSUInteger SDCacheCostForImage(UIImage *image) {
 #endif
 }
 
+// A memory cache which auto purge the cache on memory warning and support weak cache.
+@interface SDMemoryCache <KeyType, ObjectType> : NSCache <KeyType, ObjectType>
+
+@end
+
+// Private
+@interface SDMemoryCache <KeyType, ObjectType> ()
+
+@property (nonatomic, strong, nonnull) NSMapTable<KeyType, ObjectType> *weakCache; // strong-weak cache
+@property (nonatomic, strong, nonnull) dispatch_semaphore_t weakCacheLock; // a lock to keep the access to `weakCache` thread-safe
+
+@end
+
+@implementation SDMemoryCache
+
+// Current this seems no use on macOS (macOS use virtual memory and do not clear cache when memory warning). So we only override on iOS/tvOS platform.
+// But in the future there may be more options and features for this subclass.
+#if SD_UIKIT
+
+- (void)dealloc {
+    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidReceiveMemoryWarningNotification object:nil];
+}
+
+- (instancetype)init {
+    self = [super init];
+    if (self) {
+        // Use a strong-weak maptable storing the secondary cache. Follow the doc that NSCache does not copy keys
+        // This is useful when the memory warning, the cache was purged. However, the image instance can be retained by other instance such as imageViews and alive.
+        // At this case, we can sync weak cache back and do not need to load from disk cache
+        self.weakCache = [[NSMapTable alloc] initWithKeyOptions:NSPointerFunctionsStrongMemory valueOptions:NSPointerFunctionsWeakMemory capacity:0];
+        self.weakCacheLock = dispatch_semaphore_create(1);
+        [[NSNotificationCenter defaultCenter] addObserver:self
+                                                 selector:@selector(didReceiveMemoryWarning:)
+                                                     name:UIApplicationDidReceiveMemoryWarningNotification
+                                                   object:nil];
+    }
+    return self;
+}
+
+- (void)didReceiveMemoryWarning:(NSNotification *)notification {
+    // Only remove cache, but keep weak cache
+    [super removeAllObjects];
+}
+
+// `setObject:forKey:` just call this with 0 cost. Override this is enough
+- (void)setObject:(id)obj forKey:(id)key cost:(NSUInteger)g {
+    [super setObject:obj forKey:key cost:g];
+    if (key && obj) {
+        // Store weak cache
+        LOCK(self.weakCacheLock);
+        [self.weakCache setObject:obj forKey:key];
+        UNLOCK(self.weakCacheLock);
+    }
+}
+
+- (id)objectForKey:(id)key {
+    id obj = [super objectForKey:key];
+    if (key && !obj) {
+        // Check weak cache
+        LOCK(self.weakCacheLock);
+        obj = [self.weakCache objectForKey:key];
+        UNLOCK(self.weakCacheLock);
+        if (obj) {
+            // Sync cache
+            NSUInteger cost = 0;
+            if ([obj isKindOfClass:[UIImage class]]) {
+                cost = SDCacheCostForImage(obj);
+            }
+            [super setObject:obj forKey:key cost:cost];
+        }
+    }
+    return obj;
+}
+
+- (void)removeObjectForKey:(id)key {
+    [super removeObjectForKey:key];
+    if (key) {
+        // Remove weak cache
+        LOCK(self.weakCacheLock);
+        [self.weakCache removeObjectForKey:key];
+        UNLOCK(self.weakCacheLock);
+    }
+}
+
+- (void)removeAllObjects {
+    [super removeAllObjects];
+    // Manually remove should also remove weak cache
+    LOCK(self.weakCacheLock);
+    [self.weakCache removeAllObjects];
+    UNLOCK(self.weakCacheLock);
+}
+
+#endif
+
+@end
+
 @interface SDImageCache ()
 
 #pragma mark - Properties
-@property (strong, nonatomic, nonnull) NSCache *memCache;
+@property (strong, nonatomic, nonnull) SDMemoryCache *memCache;
 @property (strong, nonatomic, nonnull) NSString *diskCachePath;
 @property (strong, nonatomic, nullable) NSMutableArray<NSString *> *customPaths;
 @property (strong, nonatomic, nullable) dispatch_queue_t ioQueue;
@@ -75,7 +174,7 @@ FOUNDATION_STATIC_INLINE NSUInteger SDCacheCostForImage(UIImage *image) {
         [_config addObserver:self forKeyPath:NSStringFromSelector(@selector(maxMemoryCount)) options:0 context:SDImageCacheContext];
         
         // Init the memory cache
-        _memCache = [[NSCache alloc] init];
+        _memCache = [[SDMemoryCache alloc] init];
         _memCache.name = fullNamespace;
 
         // Init the disk cache
@@ -92,11 +191,6 @@ FOUNDATION_STATIC_INLINE NSUInteger SDCacheCostForImage(UIImage *image) {
 
 #if SD_UIKIT
         // Subscribe to app events
-        [[NSNotificationCenter defaultCenter] addObserver:self
-                                                 selector:@selector(clearMemory)
-                                                     name:UIApplicationDidReceiveMemoryWarningNotification
-                                                   object:nil];
-
         [[NSNotificationCenter defaultCenter] addObserver:self
                                                  selector:@selector(deleteOldFiles)
                                                      name:UIApplicationWillTerminateNotification

SDWebImage/UIView+WebCacheOperation.m

@@ -26,7 +26,7 @@ typedef NSMapTable<NSString *, id<SDWebImageOperation>> SDOperationsDictionary;
         if (operations) {
             return operations;
         }
-        operations = [[NSMapTable alloc] initWithKeyOptions:NSMapTableCopyIn valueOptions:NSMapTableWeakMemory capacity:0];
+        operations = [[NSMapTable alloc] initWithKeyOptions:NSPointerFunctionsStrongMemory valueOptions:NSPointerFunctionsWeakMemory capacity:0];
         objc_setAssociatedObject(self, &loadOperationKey, operations, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
         return operations;
     }

WebImage/Info.plist

@@ -15,11 +15,11 @@
 	<key>CFBundlePackageType</key>
 	<string>FMWK</string>
 	<key>CFBundleShortVersionString</key>
-	<string>4.3.0</string>
+	<string>4.3.1</string>
 	<key>CFBundleSignature</key>
 	<string>????</string>
 	<key>CFBundleVersion</key>
-	<string>4.3.0</string>
+	<string>4.3.1</string>
 	<key>NSPrincipalClass</key>
 	<string></string>
 </dict>