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Use a dispatch semaphore to keep thread safe for downloader because it need the hold cancel and add procedure be thread-safe

This commit is contained in:
DreamPiggy 2018-01-26 19:15:26 +08:00
parent f2d9abbc4a
commit 311c9e1a5e
1 changed files with 24 additions and 37 deletions
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61
SDWebImage/SDWebImageDownloader.m
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@ -9,6 +9,9 @@
#import "SDWebImageDownloader.h"
#import "SDWebImageDownloaderOperation.h"
#define LOCK(lock) dispatch_semaphore_wait(lock, DISPATCH_TIME_FOREVER);
#define UNLOCK(lock) dispatch_semaphore_signal(lock);
@interface SDWebImageDownloadToken ()
@property (nonatomic, weak, nullable) NSOperation<SDWebImageDownloaderOperationInterface> *downloadOperation;
@ -36,6 +39,7 @@
@property (assign, nonatomic, nullable) Class operationClass;
@property (strong, nonatomic, nonnull) NSMutableDictionary<NSURL *, SDWebImageDownloaderOperation *> *URLOperations;
@property (strong, nonatomic, nullable) SDHTTPHeadersMutableDictionary *HTTPHeaders;
@property (strong, nonatomic, nonnull) dispatch_semaphore_t operationsLock; // a lock to keep the access to `URLOperations` thread-safe
// The session in which data tasks will run
@property (strong, nonatomic) NSURLSession *session;
@ -94,6 +98,7 @@
#else
_HTTPHeaders = [@{@"Accept": @"image/*;q=0.8"} mutableCopy];
#endif
_operationsLock = dispatch_semaphore_create(1);
_downloadTimeout = 15.0;
[self createNewSessionWithConfiguration:sessionConfiguration];
@ -232,11 +237,15 @@
if (!url) {
return;
}
SDWebImageDownloaderOperation *operation = [self operationForURL:url];
BOOL canceled = [operation cancel:token.downloadOperationCancelToken];
if (canceled) {
[self removeOperationForURL:url];
LOCK(self.operationsLock);
SDWebImageDownloaderOperation *operation = [self.URLOperations objectForKey:url];
if (operation) {
BOOL canceled = [operation cancel:token.downloadOperationCancelToken];
if (canceled) {
[self.URLOperations removeObjectForKey:url];
}
}
UNLOCK(self.operationsLock);
}
- (nullable SDWebImageDownloadToken *)addProgressCallback:(SDWebImageDownloaderProgressBlock)progressBlock
@ -251,17 +260,24 @@
return nil;
}
SDWebImageDownloaderOperation *operation = [self operationForURL:url];
LOCK(self.operationsLock);
SDWebImageDownloaderOperation *operation = [self.URLOperations objectForKey:url];
if (!operation) {
operation = createCallback();
[self setOperation:operation forURL:url];
__weak typeof(self) wself = self;
operation.completionBlock = ^{
__strong typeof(wself) sself = wself;
[sself removeOperationForURL:url];
if (!sself) {
return;
}
LOCK(sself.operationsLock);
[sself.URLOperations removeObjectForKey:url];
UNLOCK(sself.operationsLock);
};
[self.URLOperations setObject:operation forKey:url];
}
UNLOCK(self.operationsLock);
id downloadOperationCancelToken = [operation addHandlersForProgress:progressBlock completed:completedBlock];
SDWebImageDownloadToken *token = [SDWebImageDownloadToken new];
@ -282,35 +298,6 @@
#pragma mark Helper methods
- (SDWebImageDownloaderOperation *)operationForURL:(NSURL *)url {
if (!url) {
return nil;
}
SDWebImageDownloaderOperation *operation;
@synchronized (self.URLOperations) {
operation = [self.URLOperations objectForKey:url];
}
return operation;
}
- (void)setOperation:(SDWebImageDownloaderOperation *)operation forURL:(NSURL *)url {
if (!operation || !url) {
return;
}
@synchronized (self.URLOperations) {
[self.URLOperations setObject:operation forKey:url];
}
}
- (void)removeOperationForURL:(NSURL *)url {
if (!url) {
return;
}
@synchronized (self.URLOperations) {
[self.URLOperations removeObjectForKey:url];
}
}
- (SDWebImageDownloaderOperation *)operationWithTask:(NSURLSessionTask *)task {
SDWebImageDownloaderOperation *returnOperation = nil;
for (SDWebImageDownloaderOperation *operation in self.downloadQueue.operations) {