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/*
* Copyright (c) 2015, Ford Motor Company
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 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.
*
* Neither the name of the Ford Motor Company 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 THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT HOLDER OR 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 SRC_COMPONENTS_INCLUDE_UTILS_RWLOCK_H_
#define SRC_COMPONENTS_INCLUDE_UTILS_RWLOCK_H_
#if defined(OS_POSIX)
#include <pthread.h>
#endif
#include "utils/macro.h"
namespace sync_primitives {
namespace impl {
#if defined(OS_POSIX)
typedef pthread_rwlock_t PlatformRWLock;
#else
#error Please implement rwlock for your OS
#endif
} // namespace impl
/**
* RW locks wrapper
* Read-write locks permit concurrent reads and exclusive writes to a protected shared resource.
* The read-write lock is a single entity that can be locked in read or write mode.
* To modify a resource, a thread must first acquire the exclusive write lock.
* An exclusive write lock is not permitted until all read locks have been released.
*/
class RWLock {
public:
RWLock();
~RWLock();
/**
* @brief Acqure read-write lock for reading.
* The calling thread acquires the read lock if a writer does not
* hold the lock and there are no writers blocked on the lock.
* It is unspecified whether the calling thread acquires the lock
* when a writer does not hold the lock and there are writers waiting for the lock.
* If a writer holds the lock, the calling thread will not acquire the read lock.
* If the read lock is not acquired, the calling thread blocks
* (that is, it does not return from the AcquireForReading()) until it can acquire the lock.
* Results are undefined if the calling thread holds a write lock on rwlock at the time the call is made.
* A thread can hold multiple concurrent read locks on rwlock
* (that is, successfully call AcquireForReading() n times)
* If so, the thread must perform matching unlocks (that is, it must call Release() n times).
* @returns true if lock was acquired and false if was not
*/
bool AcquireForReading();
/**
* @brief try to Acqure read-write lock for reading.
* Applies a read lock as in AcquireForReading()
* with the exception that the function fails if any thread
* holds a write lock on rwlock or there are writers blocked on rwlock.
* But not blocks calling thread.
* @returns true if lock was acquired and false if was not
*/
bool TryAcquireForReading();
/**
* @brief Try to Acqure read-write lock for writing.
* Applies a write lock like AcquireForWriting(), with the exception that the
* function fails if any thread currently holds rwlock (for reading or writing)
* Invoke of TryAcquireForWriting will not block calling thread and returns "false"
* @returns true if lock was acquired and false if was not
*/
bool TryAcquireForWriting();
/**
* @brief Acqure read-write lock for writing.
* Applies a write lock to the read-write lock.
* The calling thread acquires the write lock if no other thread (reader or writer)
* holds the read-write lock rwlock. Otherwise, the thread blocks
* (that is, does not return from the AcquireForWriting() call)
* until it can acquire the lock.
* Results are undefined if the calling thread holds the read-write lock (whether a read or write lock)
* at the time the call is made.
* The thread must perform matching unlock (that is, it must call Release()).
* @returns true if lock was acquired and false if was not
*/
bool AcquireForWriting();
/**
* @brief Release read-write lock.
* Releases a lock held on the read-write lock object.
* Results are undefined if the read-write lock rwlock
* is not held by the calling thread.
* @returns true if lock was released and false if was not
*/
bool Release();
private:
impl::PlatformRWLock rwlock_;
};
/**
* @brief Makes auto lock read-write locks for reading
* Please use AutoReadLock to acquire for reading and (automatically) release it
*/
class AutoReadLock {
public:
explicit AutoReadLock(RWLock& rwlock)
: rwlock_(rwlock) {
rwlock_.AcquireForReading();
}
~AutoReadLock() {
rwlock_.Release();
}
private:
RWLock& rwlock_;
DISALLOW_COPY_AND_ASSIGN(AutoReadLock);
};
/**
* @brief Makes auto lock read-write locks for writing
* Please use AutoWriteLock to acquire for writing and (automatically) release it
*/
class AutoWriteLock {
public:
explicit AutoWriteLock(RWLock& rwlock)
: rwlock_(rwlock) {
rwlock_.AcquireForWriting();
}
~AutoWriteLock() {
rwlock_.Release();
}
private:
RWLock& rwlock_;
DISALLOW_COPY_AND_ASSIGN(AutoWriteLock);
};
} // namespace sync_primitives
#endif // SRC_COMPONENTS_INCLUDE_UTILS_RWLOCK_H_
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