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