react-native/React/Fabric/Utils/MainRunLoopEventBeat.mm

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// Copyright (c) Facebook, Inc. and its affiliates.
// This source code is licensed under the MIT license found in the
// LICENSE file in the root directory of this source tree.
#import "MainRunLoopEventBeat.h"
#import <mutex>
#import <React/RCTUtils.h>
namespace facebook {
namespace react {
MainRunLoopEventBeat::MainRunLoopEventBeat(std::shared_ptr<MessageQueueThread> messageQueueThread):
messageQueueThread_(std::move(messageQueueThread)) {
mainRunLoopObserver_ =
CFRunLoopObserverCreateWithHandler(
NULL /* allocator */,
kCFRunLoopBeforeWaiting /* activities */,
true /* repeats */,
0 /* order */,
^(CFRunLoopObserverRef observer, CFRunLoopActivity activity) {
if (!this->isRequested_) {
return;
}
this->blockMessageQueueAndThenBeat();
}
);
assert(mainRunLoopObserver_);
CFRunLoopAddObserver(CFRunLoopGetMain(), mainRunLoopObserver_, kCFRunLoopCommonModes);
}
MainRunLoopEventBeat::~MainRunLoopEventBeat() {
CFRunLoopRemoveObserver(CFRunLoopGetMain(), mainRunLoopObserver_, kCFRunLoopCommonModes);
CFRelease(mainRunLoopObserver_);
}
void MainRunLoopEventBeat::induce() const {
if (!this->isRequested_) {
return;
}
RCTExecuteOnMainQueue(^{
this->blockMessageQueueAndThenBeat();
});
}
void MainRunLoopEventBeat::blockMessageQueueAndThenBeat() const {
// Note: We need the third mutex to get back to the main thread before
// the lambda is finished (because all mutexes are allocated on the stack).
std::mutex mutex1;
std::mutex mutex2;
std::mutex mutex3;
mutex1.lock();
mutex2.lock();
mutex3.lock();
messageQueueThread_->runOnQueue([&]() {
mutex1.unlock();
mutex2.lock();
mutex3.unlock();
});
mutex1.lock();
beat();
mutex2.unlock();
mutex3.lock();
}
} // namespace react
} // namespace facebook