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138 lines
3.2 KiB
C++
138 lines
3.2 KiB
C++
//
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// Condition.h
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//
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// Library: Foundation
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// Package: Threading
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// Module: Condition
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//
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// Definition of the Condition class template.
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//
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// Copyright (c) 2007, Applied Informatics Software Engineering GmbH.
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// and Contributors.
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//
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// SPDX-License-Identifier: BSL-1.0
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//
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#ifndef Foundation_Condition_INCLUDED
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#define Foundation_Condition_INCLUDED
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#include "Poco/Foundation.h"
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#include "Poco/Mutex.h"
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#include "Poco/ScopedUnlock.h"
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#include "Poco/Event.h"
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#include "Poco/Exception.h"
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#include <deque>
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namespace Poco {
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class Foundation_API Condition
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/// A Condition is a synchronization object used to block a thread
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/// until a particular condition is met.
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/// A Condition object is always used in conjunction with
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/// a Mutex (or FastMutex) object.
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///
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/// Condition objects are similar to POSIX condition variables, which the
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/// difference that Condition is not subject to spurious wakeups.
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///
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/// Threads waiting on a Condition are resumed in FIFO order.
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{
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public:
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Condition();
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/// Creates the Condition.
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~Condition();
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/// Destroys the Condition.
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template <class Mtx>
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void wait(Mtx& mutex)
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/// Unlocks the mutex (which must be locked upon calling
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/// wait()) and waits until the Condition is signalled.
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///
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/// The given mutex will be locked again upon
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/// leaving the function, even in case of an exception.
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{
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ScopedUnlock<Mtx> unlock(mutex, false);
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Event event;
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{
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FastMutex::ScopedLock lock(_mutex);
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mutex.unlock();
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enqueue(event);
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}
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event.wait();
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}
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template <class Mtx>
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void wait(Mtx& mutex, long milliseconds)
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/// Unlocks the mutex (which must be locked upon calling
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/// wait()) and waits for the given time until the Condition is signalled.
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///
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/// The given mutex will be locked again upon successfully leaving the
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/// function, even in case of an exception.
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///
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/// Throws a TimeoutException if the Condition is not signalled
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/// within the given time interval.
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{
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if (!tryWait(mutex, milliseconds))
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throw TimeoutException();
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}
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template <class Mtx>
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bool tryWait(Mtx& mutex, long milliseconds)
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/// Unlocks the mutex (which must be locked upon calling
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/// tryWait()) and waits for the given time until the Condition is signalled.
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///
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/// The given mutex will be locked again upon leaving the
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/// function, even in case of an exception.
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///
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/// Returns true if the Condition has been signalled
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/// within the given time interval, otherwise false.
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{
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ScopedUnlock<Mtx> unlock(mutex, false);
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Event event;
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{
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FastMutex::ScopedLock lock(_mutex);
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mutex.unlock();
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enqueue(event);
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}
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if (!event.tryWait(milliseconds))
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{
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FastMutex::ScopedLock lock(_mutex);
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dequeue(event);
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return false;
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}
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return true;
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}
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void signal();
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/// Signals the Condition and allows one waiting thread
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/// to continue execution.
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void broadcast();
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/// Signals the Condition and allows all waiting
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/// threads to continue their execution.
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protected:
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void enqueue(Event& event);
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void dequeue();
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void dequeue(Event& event);
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private:
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Condition(const Condition&);
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Condition& operator = (const Condition&);
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typedef std::deque<Event*> WaitQueue;
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FastMutex _mutex;
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WaitQueue _waitQueue;
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};
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} // namespace Poco
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#endif // Foundation_Condition_INCLUDED
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