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/*
* Copyright 2015 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkSpinlock_DEFINED
#define SkSpinlock_DEFINED
#include "include/core/SkTypes.h"
#include "include/private/base/SkThreadAnnotations.h"
#include <atomic>
class SK_CAPABILITY("mutex") SkSpinlock {
public:
constexpr SkSpinlock() = default;
void acquire() SK_ACQUIRE() {
// To act as a mutex, we need an acquire barrier when we acquire the lock.
if (fLocked.exchange(true, std::memory_order_acquire)) {
// Lock was contended. Fall back to an out-of-line spin loop.
this->contendedAcquire();
}
}
// Acquire the lock or fail (quickly). Lets the caller decide to do something other than wait.
bool tryAcquire() SK_TRY_ACQUIRE(true) {
// To act as a mutex, we need an acquire barrier when we acquire the lock.
if (fLocked.exchange(true, std::memory_order_acquire)) {
// Lock was contended. Let the caller decide what to do.
return false;
}
return true;
}
void release() SK_RELEASE_CAPABILITY() {
// To act as a mutex, we need a release barrier when we release the lock.
fLocked.store(false, std::memory_order_release);
}
private:
SK_API void contendedAcquire();
std::atomic<bool> fLocked{false};
};
class SK_SCOPED_CAPABILITY SkAutoSpinlock {
public:
SkAutoSpinlock(SkSpinlock& mutex) SK_ACQUIRE(mutex) : fSpinlock(mutex) { fSpinlock.acquire(); }
~SkAutoSpinlock() SK_RELEASE_CAPABILITY() { fSpinlock.release(); }
private:
SkSpinlock& fSpinlock;
};
#endif//SkSpinlock_DEFINED
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