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[ios] Updated completion handler call on concurrent fetch tasks.

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This commit is contained in:
Ilya Grechuhin 2016-01-27 10:37:56 +03:00 • committed by Sergey Yershov
parent 164aaf7be4
commit 6f19401ac8
1 changed files with 29 additions and 18 deletions
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47
iphone/Maps/Classes/MapsAppDelegate.mm
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@ -405,14 +405,20 @@ void InitLocalizedStrings()
- (void)application:(UIApplication *)application performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler
{
static mutex fetchTaskMutex;
// At the moment, we need to perform 3 asynchronous background tasks simultaneously.
// We will force complete fetch before backgroundTimeRemaining.
// However if all scheduled tasks complete before backgroundTimeRemaining, fetch completes as soon as last task finishes.
// fetchResultPriority is used to determine result we must send to fetch completion block.
// Threads synchronization is made through dispatch_async on the main queue.
static NSUInteger fetchRunningTasks;
static UIBackgroundFetchResult fetchResult;
static NSUInteger fetchStamp = 0;
NSUInteger const taskFetchStamp = fetchStamp;
fetchRunningTasks = 0;
fetchResult = UIBackgroundFetchResultNewData;
auto fetchResultPriority = ^NSUInteger(UIBackgroundFetchResult result)
auto const fetchResultPriority = ^NSUInteger(UIBackgroundFetchResult result)
{
switch (result)
{
@ -421,32 +427,37 @@ void InitLocalizedStrings()
case UIBackgroundFetchResultFailed: return 3;
}
};
auto callback = ^(UIBackgroundFetchResult result)
auto const callback = ^(UIBackgroundFetchResult result)
{
lock_guard<mutex> lock(fetchTaskMutex);
if (fetchResultPriority(fetchResult) < fetchResultPriority(result))
fetchResult = result;
if (--fetchRunningTasks == 0)
completionHandler(fetchResult);
dispatch_async(dispatch_get_main_queue(), ^
{
if (taskFetchStamp != fetchStamp)
return;
if (fetchResultPriority(fetchResult) < fetchResultPriority(result))
fetchResult = result;
if (--fetchRunningTasks == 0)
{
fetchStamp++;
completionHandler(fetchResult);
}
});
};
using TTaskBlock = void(^)();
auto runFetchTask = ^(TTaskBlock task)
auto const runFetchTask = ^(TMWMVoidBlock task)
{
lock_guard<mutex> lock(fetchTaskMutex);
++fetchRunningTasks;
task();
};
dispatch_time_t const whenForceComplete = dispatch_time(
DISPATCH_TIME_NOW, static_cast<int64_t>(UIApplication.sharedApplication.backgroundTimeRemaining) * NSEC_PER_SEC);
dispatch_after(whenForceComplete, dispatch_get_main_queue(), ^
dispatch_time_t const forceCompleteTime = dispatch_time(
DISPATCH_TIME_NOW, static_cast<int64_t>(application.backgroundTimeRemaining) * NSEC_PER_SEC);
dispatch_after(forceCompleteTime, dispatch_get_main_queue(), ^
{
lock_guard<mutex> lock(fetchTaskMutex);
fetchRunningTasks = 0;
completionHandler(fetchResult);
if (taskFetchStamp != fetchStamp)
return;
fetchRunningTasks = 1;
callback(fetchResult);
});
// At the moment, we need to perform 3 asynchronous background tasks simultaneously:
// 1. Try to send collected statistics (if any) to our server.
runFetchTask(^
{