| /* |
| * Copyright (C) 2008-2017 Apple Inc. All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. Neither the name of Apple Inc. ("Apple") nor the names of |
| * its contributors may be used to endorse or promote products derived |
| * from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY |
| * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
| * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
| * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY |
| * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
| * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
| * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
| * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| #ifndef Locker_h |
| #define Locker_h |
| |
| #include <wtf/Assertions.h> |
| #include <wtf/Atomics.h> |
| #include <wtf/Noncopyable.h> |
| |
| namespace WTF { |
| |
| enum NoLockingNecessaryTag { NoLockingNecessary }; |
| |
| class AbstractLocker { |
| WTF_MAKE_NONCOPYABLE(AbstractLocker); |
| public: |
| AbstractLocker(NoLockingNecessaryTag) |
| { |
| } |
| |
| protected: |
| AbstractLocker() |
| { |
| } |
| }; |
| |
| template <typename T> class Locker : public AbstractLocker { |
| public: |
| explicit Locker(T& lockable) : m_lockable(&lockable) { lock(); } |
| explicit Locker(T* lockable) : m_lockable(lockable) { lock(); } |
| |
| // You should be wary of using this constructor. It's only applicable |
| // in places where there is a locking protocol for a particular object |
| // but it's not necessary to engage in that protocol yet. For example, |
| // this often happens when an object is newly allocated and it can not |
| // be accessed concurrently. |
| Locker(NoLockingNecessaryTag) : m_lockable(nullptr) { } |
| |
| Locker(int) = delete; |
| |
| ~Locker() |
| { |
| compilerFence(); |
| if (m_lockable) |
| m_lockable->unlock(); |
| } |
| |
| static Locker tryLock(T& lockable) |
| { |
| Locker result(NoLockingNecessary); |
| if (lockable.tryLock()) { |
| result.m_lockable = &lockable; |
| return result; |
| } |
| return result; |
| } |
| |
| explicit operator bool() const { return !!m_lockable; } |
| |
| void unlockEarly() |
| { |
| m_lockable->unlock(); |
| m_lockable = 0; |
| } |
| |
| // It's great to be able to pass lockers around. It enables custom locking adaptors like |
| // JSC::LockDuringMarking. |
| Locker(Locker&& other) |
| : m_lockable(other.m_lockable) |
| { |
| other.m_lockable = nullptr; |
| } |
| |
| Locker& operator=(Locker&& other) |
| { |
| if (m_lockable) |
| m_lockable->unlock(); |
| m_lockable = other.m_lockable; |
| other.m_lockable = nullptr; |
| return *this; |
| } |
| |
| private: |
| void lock() |
| { |
| if (m_lockable) |
| m_lockable->lock(); |
| compilerFence(); |
| } |
| |
| T* m_lockable; |
| }; |
| |
| // Use this lock scope like so: |
| // auto locker = holdLock(lock); |
| template<typename LockType> |
| Locker<LockType> holdLock(LockType& lock) |
| { |
| return Locker<LockType>(lock); |
| } |
| |
| template<typename LockType> |
| Locker<LockType> holdLockIf(LockType& lock, bool predicate) |
| { |
| return Locker<LockType>(predicate ? &lock : nullptr); |
| } |
| |
| template<typename LockType> |
| Locker<LockType> tryHoldLock(LockType& lock) |
| { |
| return Locker<LockType>::tryLock(lock); |
| } |
| |
| } |
| |
| using WTF::AbstractLocker; |
| using WTF::Locker; |
| using WTF::NoLockingNecessaryTag; |
| using WTF::NoLockingNecessary; |
| using WTF::holdLock; |
| using WTF::holdLockIf; |
| |
| #endif |