1/*
2 * Copyright 2015 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8// This file is not part of the public Skia API.
9
10#ifndef SkSpinlock_DEFINED
11#define SkSpinlock_DEFINED
12
13#include "../private/SkAtomics.h"
14
15#define SK_DECLARE_STATIC_SPINLOCK(name) namespace {} static SkPODSpinlock name
16
17// This class has no constructor and must be zero-initialized (the macro above does this).
18class SK_API SkPODSpinlock {
19public:
20    void acquire() {
21        // To act as a mutex, we need an acquire barrier if we take the lock.
22        if (sk_atomic_exchange(&fLocked, true, sk_memory_order_acquire)) {
23            // Lock was contended.  Fall back to an out-of-line spin loop.
24            this->contendedAcquire();
25        }
26    }
27
28    void release() {
29        // To act as a mutex, we need a release barrier.
30        sk_atomic_store(&fLocked, false, sk_memory_order_release);
31    }
32
33private:
34    void contendedAcquire();
35    bool fLocked;
36};
37
38// For non-global-static use cases, this is normally what you want.
39class SkSpinlock : public SkPODSpinlock {
40public:
41    SkSpinlock() { this->release(); }
42};
43
44#endif//SkSpinlock_DEFINED
45