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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_SYNCHRONIZATION_LOCK_IMPL_H_
#define BASE_SYNCHRONIZATION_LOCK_IMPL_H_
#include "base/base_export.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/thread_annotations.h"
#include "build/build_config.h"
#if defined(OS_WIN)
#include "base/win/windows_types.h"
#elif defined(OS_POSIX) || defined(OS_FUCHSIA)
#include <errno.h>
#include <pthread.h>
#endif
namespace base {
namespace internal {
// This class implements the underlying platform-specific spin-lock mechanism
// used for the Lock class. Most users should not use LockImpl directly, but
// should instead use Lock.
class BASE_EXPORT LockImpl {
public:
#if defined(OS_WIN)
using NativeHandle = CHROME_SRWLOCK;
#elif defined(OS_POSIX) || defined(OS_FUCHSIA)
using NativeHandle = pthread_mutex_t;
#endif
LockImpl();
~LockImpl();
// If the lock is not held, take it and return true. If the lock is already
// held by something else, immediately return false.
bool Try();
// Take the lock, blocking until it is available if necessary.
void Lock();
// Release the lock. This must only be called by the lock's holder: after
// a successful call to Try, or a call to Lock.
inline void Unlock();
// Return the native underlying lock.
// TODO(awalker): refactor lock and condition variables so that this is
// unnecessary.
NativeHandle* native_handle() { return &native_handle_; }
#if defined(OS_POSIX) || defined(OS_FUCHSIA)
// Whether this lock will attempt to use priority inheritance.
static bool PriorityInheritanceAvailable();
#endif
private:
NativeHandle native_handle_;
DISALLOW_COPY_AND_ASSIGN(LockImpl);
};
#if defined(OS_WIN)
void LockImpl::Unlock() {
::ReleaseSRWLockExclusive(reinterpret_cast<PSRWLOCK>(&native_handle_));
}
#elif defined(OS_POSIX) || defined(OS_FUCHSIA)
void LockImpl::Unlock() {
int rv = pthread_mutex_unlock(&native_handle_);
DCHECK_EQ(rv, 0) << ". " << strerror(rv);
}
#endif
// This is an implementation used for AutoLock templated on the lock type.
template <class LockType>
class SCOPED_LOCKABLE BasicAutoLock {
public:
struct AlreadyAcquired {};
explicit BasicAutoLock(LockType& lock) EXCLUSIVE_LOCK_FUNCTION(lock)
: lock_(lock) {
lock_.Acquire();
}
BasicAutoLock(LockType& lock, const AlreadyAcquired&)
EXCLUSIVE_LOCKS_REQUIRED(lock)
: lock_(lock) {
lock_.AssertAcquired();
}
~BasicAutoLock() UNLOCK_FUNCTION() {
lock_.AssertAcquired();
lock_.Release();
}
private:
LockType& lock_;
DISALLOW_COPY_AND_ASSIGN(BasicAutoLock);
};
// This is an implementation used for AutoUnlock templated on the lock type.
template <class LockType>
class BasicAutoUnlock {
public:
explicit BasicAutoUnlock(LockType& lock) : lock_(lock) {
// We require our caller to have the lock.
lock_.AssertAcquired();
lock_.Release();
}
~BasicAutoUnlock() { lock_.Acquire(); }
private:
LockType& lock_;
DISALLOW_COPY_AND_ASSIGN(BasicAutoUnlock);
};
// This is an implementation used for AutoLockMaybe templated on the lock type.
template <class LockType>
class SCOPED_LOCKABLE BasicAutoLockMaybe {
public:
explicit BasicAutoLockMaybe(LockType* lock) EXCLUSIVE_LOCK_FUNCTION(lock)
: lock_(lock) {
if (lock_)
lock_->Acquire();
}
~BasicAutoLockMaybe() UNLOCK_FUNCTION() {
if (lock_) {
lock_->AssertAcquired();
lock_->Release();
}
}
private:
LockType* const lock_;
DISALLOW_COPY_AND_ASSIGN(BasicAutoLockMaybe);
};
// This is an implementation used for ReleasableAutoLock templated on the lock
// type.
template <class LockType>
class SCOPED_LOCKABLE BasicReleasableAutoLock {
public:
explicit BasicReleasableAutoLock(LockType* lock) EXCLUSIVE_LOCK_FUNCTION(lock)
: lock_(lock) {
DCHECK(lock_);
lock_->Acquire();
}
~BasicReleasableAutoLock() UNLOCK_FUNCTION() {
if (lock_) {
lock_->AssertAcquired();
lock_->Release();
}
}
void Release() UNLOCK_FUNCTION() {
DCHECK(lock_);
lock_->AssertAcquired();
lock_->Release();
lock_ = nullptr;
}
private:
LockType* lock_;
DISALLOW_COPY_AND_ASSIGN(BasicReleasableAutoLock);
};
} // namespace internal
} // namespace base
#endif // BASE_SYNCHRONIZATION_LOCK_IMPL_H_