126 lines
3.3 KiB
C++
126 lines
3.3 KiB
C++
/*
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* Copyright 2015 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkMutex_DEFINED
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#define SkMutex_DEFINED
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// This file is not part of the public Skia API.
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#include "../private/SkSemaphore.h"
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#include "SkTypes.h"
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#ifdef SK_DEBUG
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#include "../private/SkThreadID.h"
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#endif
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#define SK_MUTEX_SEMAPHORE_INIT {1, {0}}
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#ifdef SK_DEBUG
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#define SK_BASE_MUTEX_INIT {SK_MUTEX_SEMAPHORE_INIT, 0}
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#else
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#define SK_BASE_MUTEX_INIT {SK_MUTEX_SEMAPHORE_INIT}
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#endif
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// Using POD-style initialization prevents the generation of a static initializer.
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//
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// Without magic statics there are no thread safety guarantees on initialization
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// of local statics (even POD). As a result, it is illegal to use
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// SK_DECLARE_STATIC_MUTEX in a function.
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//
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// Because SkBaseMutex is not a primitive, a static SkBaseMutex cannot be
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// initialized in a class with this macro.
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#define SK_DECLARE_STATIC_MUTEX(name) namespace {} static SkBaseMutex name = SK_BASE_MUTEX_INIT;
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struct SkBaseMutex {
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void acquire() {
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fSemaphore.wait();
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SkDEBUGCODE(fOwner = SkGetThreadID();)
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}
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void release() {
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this->assertHeld();
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SkDEBUGCODE(fOwner = kIllegalThreadID;)
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fSemaphore.signal();
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}
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void assertHeld() {
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SkASSERT(fOwner == SkGetThreadID());
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}
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SkBaseSemaphore fSemaphore;
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SkDEBUGCODE(SkThreadID fOwner;)
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};
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// This needs to use subclassing instead of encapsulation to make SkAutoMutexAcquire to work.
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class SkMutex : public SkBaseMutex {
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public:
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SkMutex () {
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fSemaphore = SK_MUTEX_SEMAPHORE_INIT;
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SkDEBUGCODE(fOwner = kIllegalThreadID);
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}
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~SkMutex () { fSemaphore.deleteSemaphore(); }
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SkMutex(const SkMutex&) = delete;
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SkMutex& operator=(const SkMutex&) = delete;
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};
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template <typename Lock>
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class SkAutoTAcquire : SkNoncopyable {
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public:
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explicit SkAutoTAcquire(Lock& mutex) : fMutex(&mutex) {
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SkASSERT(fMutex != nullptr);
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mutex.acquire();
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}
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explicit SkAutoTAcquire(Lock* mutex) : fMutex(mutex) {
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if (mutex) {
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mutex->acquire();
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}
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}
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/** If the mutex has not been released, release it now. */
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~SkAutoTAcquire() {
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if (fMutex) {
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fMutex->release();
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}
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}
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/** If the mutex has not been released, release it now. */
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void release() {
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if (fMutex) {
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fMutex->release();
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fMutex = nullptr;
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}
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}
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/** Assert that we're holding the mutex. */
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void assertHeld() {
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SkASSERT(fMutex);
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fMutex->assertHeld();
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}
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private:
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Lock* fMutex;
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};
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// SkAutoTExclusive is a lighter weight version of SkAutoTAcquire. It assumes that there is a valid
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// mutex, thus removing the check for the null pointer.
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template <typename Lock>
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class SkAutoTExclusive {
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public:
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SkAutoTExclusive(Lock& lock) : fLock(lock) { lock.acquire(); }
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~SkAutoTExclusive() { fLock.release(); }
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private:
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Lock &fLock;
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};
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typedef SkAutoTAcquire<SkBaseMutex> SkAutoMutexAcquire;
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#define SkAutoMutexAcquire(...) SK_REQUIRE_LOCAL_VAR(SkAutoMutexAcquire)
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typedef SkAutoTExclusive<SkBaseMutex> SkAutoMutexExclusive;
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#define SkAutoMutexExclusive(...) SK_REQUIRE_LOCAL_VAR(SkAutoMutexExclusive)
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#endif//SkMutex_DEFINED
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