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/*
* Copyright (c) 2013, 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_CONDITIONAL_VARIABLE_H_
#define SRC_COMPONENTS_INCLUDE_UTILS_CONDITIONAL_VARIABLE_H_
#if defined(OS_POSIX)
#include <pthread.h>
#else
#error Please implement conditional variable for your OS
#endif
#include <stdint.h>
#include "utils/macro.h"
namespace sync_primitives {
class AutoLock;
class Lock;
namespace impl {
#if defined(OS_POSIX)
typedef pthread_cond_t PlatformConditionalVariable;
#endif
} // namespace impl
/*
* Conditional variable wrapper
* Conditional variable is a thing that can be waited on
* Wait is finished when other thread puts that thing in a signaled state
* (or when timeout is over).
* Data that is conditionally accessed should be protected by
* a Lock and that lock must be taken before starting to Wait.
* When wait is performed, Lock is temporarly released.
* When wait is finished, Lock is captured back.
* WARNING: Beware of Spurious wakeups
* http://en.wikipedia.org/wiki/Spurious_wakeup
* Thread can wake up from wait spuriously, without conditional
* variable being actually set by other thread. This means
* additional check should be made right after thread awakening
* and if check fails thread should continue waiting.
*
* while(!DataReady()) cond_var.Wait(auto_lock);
*
*/
class ConditionalVariable {
public:
enum WaitStatus { kNoTimeout, kTimeout };
ConditionalVariable();
~ConditionalVariable();
// Wakes up single thread that is waiting on this conditional variable
void NotifyOne();
// Wakes up all waiting threads
void Broadcast();
// Wait forever or up to milliseconds time limit
bool Wait(AutoLock& auto_lock);
bool Wait(Lock& lock);
WaitStatus WaitFor(AutoLock& auto_lock, uint32_t milliseconds);
private:
impl::PlatformConditionalVariable cond_var_;
private:
DISALLOW_COPY_AND_ASSIGN(ConditionalVariable);
};
} // namespace sync_primitives
#endif // SRC_COMPONENTS_INCLUDE_UTILS_CONDITIONAL_VARIABLE_H_
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