Add download resume support (#3246)

* Adds support for resuming downloads that were canceled due to exiting preload range. * Update to latest PINRemoteImage * Fix warnings * Address comments. Thanks @nguyenhuy!
facebookarchive · Apr 10, 2017 · 68a8d5f · 68a8d5f
1 parent 582bca9
commit 68a8d5f
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Showing 4 changed files with 40 additions and 17 deletions.
diff --git a/AsyncDisplayKit.podspec b/AsyncDisplayKit.podspec
@@ -44,7 +44,7 @@ Pod::Spec.new do |spec|
   end
 
   spec.subspec 'PINRemoteImage' do |pin|
-      pin.dependency 'PINRemoteImage/iOS', '= 3.0.0-beta.8'
+      pin.dependency 'PINRemoteImage/iOS', '= 3.0.0-beta.9'
       pin.dependency 'PINRemoteImage/PINCache'
       pin.dependency 'AsyncDisplayKit/Core'
   end

diff --git a/Source/ASNetworkImageNode.mm b/Source/ASNetworkImageNode.mm
@@ -58,6 +58,7 @@ @interface ASNetworkImageNode ()
     unsigned int downloaderImplementsSetProgress:1;
     unsigned int downloaderImplementsSetPriority:1;
     unsigned int downloaderImplementsAnimatedImage:1;
+    unsigned int downloaderImplementsCancelWithResume:1;
   } _downloaderFlags;
 
   // Immutable and set on init only. We don't need to lock in this case.
@@ -85,6 +86,7 @@ - (instancetype)initWithCache:(id<ASImageCacheProtocol>)cache downloader:(id<ASI
   _downloaderFlags.downloaderImplementsSetProgress = [downloader respondsToSelector:@selector(setProgressImageBlock:callbackQueue:withDownloadIdentifier:)];
   _downloaderFlags.downloaderImplementsSetPriority = [downloader respondsToSelector:@selector(setPriority:withDownloadIdentifier:)];
   _downloaderFlags.downloaderImplementsAnimatedImage = [downloader respondsToSelector:@selector(animatedImageWithData:)];
+  _downloaderFlags.downloaderImplementsCancelWithResume = [downloader respondsToSelector:@selector(cancelImageDownloadWithResumePossibilityForIdentifier:)];
 
   _cacheFlags.cacheSupportsClearing = [cache respondsToSelector:@selector(clearFetchedImageFromCacheWithURL:)];
   _cacheFlags.cacheSupportsSynchronousFetch = [cache respondsToSelector:@selector(synchronouslyFetchedCachedImageWithURL:)];
@@ -107,7 +109,7 @@ - (instancetype)init
 
 - (void)dealloc
 {
-  [self _cancelImageDownload];
+  [self _cancelImageDownloadWithResumePossibility:NO];
 }
 
 #pragma mark - Public methods -- must lock
@@ -127,7 +129,7 @@ - (void)_locked_setImage:(UIImage *)image
   if (shouldCancelAndClear) {
     ASDisplayNodeAssertNil(_URL, @"Directly setting an image on an ASNetworkImageNode causes it to behave like an ASImageNode instead of an ASNetworkImageNode. If this is what you want, set the URL to nil first.");
     _URL = nil;
-    [self _locked_cancelDownloadAndClearImage];
+    [self _locked_cancelDownloadAndClearImageWithResumePossibility:NO];
   }
 
   [self _locked__setImage:image];
@@ -163,7 +165,7 @@ - (void)setURL:(NSURL *)URL resetToDefault:(BOOL)reset
       return;
     }
 
-    [self _locked_cancelImageDownload];
+    [self _locked_cancelImageDownloadWithResumePossibility:NO];
 
     _imageLoaded = NO;
 
@@ -385,7 +387,7 @@ - (void)didExitPreloadState
     return;
   }
 
-  [self _cancelDownloadAndClearImage];
+  [self _cancelDownloadAndClearImageWithResumePossibility:YES];
 }
 
 - (void)didEnterPreloadState
@@ -469,15 +471,15 @@ - (void)_updateProgressImageBlockOnDownloaderIfNeeded
   }
 }
 
-- (void)_cancelDownloadAndClearImage
+- (void)_cancelDownloadAndClearImageWithResumePossibility:(BOOL)storeResume
 {
   ASDN::MutexLocker l(__instanceLock__);
-  [self _locked_cancelDownloadAndClearImage];
+  [self _locked_cancelDownloadAndClearImageWithResumePossibility:storeResume];
 }
 
-- (void)_locked_cancelDownloadAndClearImage
+- (void)_locked_cancelDownloadAndClearImageWithResumePossibility:(BOOL)storeResume
 {
-  [self _locked_cancelImageDownload];
+  [self _locked_cancelImageDownloadWithResumePossibility:storeResume];
 
   // Destruction of bigger images on the main thread can be expensive
   // and can take some time, so we dispatch onto a bg queue to
@@ -504,20 +506,24 @@ - (void)_locked_cancelDownloadAndClearImage
   }
 }
 
-- (void)_cancelImageDownload
+- (void)_cancelImageDownloadWithResumePossibility:(BOOL)storeResume
 {
   ASDN::MutexLocker l(__instanceLock__);
-  [self _locked_cancelImageDownload];
+  [self _locked_cancelImageDownloadWithResumePossibility:storeResume];
 }
 
-- (void)_locked_cancelImageDownload
+- (void)_locked_cancelImageDownloadWithResumePossibility:(BOOL)storeResume
 {
   if (!_downloadIdentifier) {
     return;
   }
 
   if (_downloadIdentifier) {
-    [_downloader cancelImageDownloadForIdentifier:_downloadIdentifier];
+    if (storeResume && _downloaderFlags.downloaderImplementsCancelWithResume) {
+      [_downloader cancelImageDownloadWithResumePossibilityForIdentifier:_downloadIdentifier];
+    } else {
+      [_downloader cancelImageDownloadForIdentifier:_downloadIdentifier];
+    }
   }
   _downloadIdentifier = nil;
 

diff --git a/Source/Details/ASImageProtocols.h b/Source/Details/ASImageProtocols.h
@@ -109,6 +109,17 @@ typedef NS_ENUM(NSUInteger, ASImageDownloaderPriority) {
 
 @optional
 
+/**
+ @abstract Cancels an image download, however indicating resume data should be stored in case of redownload.
+ @param downloadIdentifier The opaque download identifier object returned from
+ `downloadImageWithURL:callbackQueue:downloadProgressBlock:completion:`.
+ @discussion This method has no effect if `downloadIdentifier` is nil. If implemented, this method
+ may be called instead of `cancelImageDownloadForIdentifier:` in cases where ASDK believes there's a chance
+ the image download will be resumed (currently when an image exits preload range). You can use this to store
+ any data that has already been downloaded for use in resuming the download later.
+ */
+- (void)cancelImageDownloadWithResumePossibilityForIdentifier:(id)downloadIdentifier;
+
 /**
  @abstract Return an object that conforms to ASAnimatedImageProtocol
  @param animatedImageData Data that represents an animated image.

diff --git a/Source/Details/ASPINRemoteImageDownloader.m b/Source/Details/ASPINRemoteImageDownloader.m
@@ -245,7 +245,13 @@ - (nullable id)downloadImageWithURL:(NSURL *)URL
 - (void)cancelImageDownloadForIdentifier:(id)downloadIdentifier
 {
   ASDisplayNodeAssert([downloadIdentifier isKindOfClass:[NSUUID class]], @"downloadIdentifier must be NSUUID");
-  [[self sharedPINRemoteImageManager] cancelTaskWithUUID:downloadIdentifier];
+  [[self sharedPINRemoteImageManager] cancelTaskWithUUID:downloadIdentifier storeResumeData:NO];
+}
+
+- (void)cancelImageDownloadWithResumePossibilityForIdentifier:(id)downloadIdentifier
+{
+  ASDisplayNodeAssert([downloadIdentifier isKindOfClass:[NSUUID class]], @"downloadIdentifier must be NSUUID");
+  [[self sharedPINRemoteImageManager] cancelTaskWithUUID:downloadIdentifier storeResumeData:YES];
 }
 
 - (void)setProgressImageBlock:(ASImageDownloaderProgressImage)progressBlock callbackQueue:(dispatch_queue_t)callbackQueue withDownloadIdentifier:(id)downloadIdentifier
@@ -270,15 +276,15 @@ - (void)setPriority:(ASImageDownloaderPriority)priority withDownloadIdentifier:(
   PINRemoteImageManagerPriority pi_priority = PINRemoteImageManagerPriorityMedium;
   switch (priority) {
     case ASImageDownloaderPriorityPreload:
-      pi_priority = PINRemoteImageManagerPriorityMedium;
+      pi_priority = PINRemoteImageManagerPriorityLow;
       break;
 
     case ASImageDownloaderPriorityImminent:
-      pi_priority = PINRemoteImageManagerPriorityHigh;
+      pi_priority = PINRemoteImageManagerPriorityDefault;
       break;
 
     case ASImageDownloaderPriorityVisible:
-      pi_priority = PINRemoteImageManagerPriorityVeryHigh;
+      pi_priority = PINRemoteImageManagerPriorityHigh;
       break;
   }
   [[self sharedPINRemoteImageManager] setPriority:pi_priority ofTaskWithUUID:downloadIdentifier];