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Fix the issue that "There may be no complete callback when download the picture of the local path"

This commit is contained in:
DreamPiggy 2019-12-26 17:38:46 +08:00
parent 6ea9a7640a
commit 482d45dc65
1 changed files with 17 additions and 10 deletions
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13
SDWebImage/SDWebImageDownloader.m
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@ -293,6 +293,7 @@
}
LOCK(self.operationsLock);
id downloadOperationCancelToken;
NSOperation<SDWebImageDownloaderOperationInterface> *operation = [self.URLOperations objectForKey:url];
// There is a case that the operation may be marked as finished or cancelled, but not been removed from `self.URLOperations`.
if (!operation || operation.isFinished || operation.isCancelled) {
@ -308,11 +309,18 @@
UNLOCK(sself.operationsLock);
};
[self.URLOperations setObject:operation forKey:url];
// Add the handlers before submitting to operation queue, avoid the race condition that operation finished before setting handlers.
downloadOperationCancelToken = [operation addHandlersForProgress:progressBlock completed:completedBlock];
// Add operation to operation queue only after all configuration done according to Apple's doc.
// `addOperation:` does not synchronously execute the `operation.completionBlock` so this will not cause deadlock.
[self.downloadQueue addOperation:operation];
} else {
// When we reuse the download operation to attach more callbacks, there may be thread safe issue because the getter of callbacks may in another queue (decoding queue or delegate queue)
// So we lock the operation here, and in `SDWebImageDownloaderOperation`, we use `@synchonzied (self)`, to ensure the thread safe between these two classes.
@synchronized (operation) {
downloadOperationCancelToken = [operation addHandlersForProgress:progressBlock completed:completedBlock];
}
else if (!operation.isExecuting) {
if (!operation.isExecuting) {
if (options & SDWebImageDownloaderHighPriority) {
operation.queuePriority = NSOperationQueuePriorityHigh;
} else if (options & SDWebImageDownloaderLowPriority) {
@ -321,10 +329,9 @@
operation.queuePriority = NSOperationQueuePriorityNormal;
}
}
}
UNLOCK(self.operationsLock);
id downloadOperationCancelToken = [operation addHandlersForProgress:progressBlock completed:completedBlock];
SDWebImageDownloadToken *token = [SDWebImageDownloadToken new];
token.downloadOperation = operation;
token.url = url;