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//
// Semaphore.h
//
// Library: Foundation
// Package: Threading
// Module: Semaphore
//
// Definition of the Semaphore class.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier: BSL-1.0
//
#ifndef Foundation_Semaphore_INCLUDED
#define Foundation_Semaphore_INCLUDED
#include "Poco/Foundation.h"
#include "Poco/Exception.h"
#if defined(POCO_OS_FAMILY_WINDOWS)
#include "Poco/Semaphore_WIN32.h"
#elif defined(POCO_VXWORKS)
#include "Poco/Semaphore_VX.h"
#else
#include "Poco/Semaphore_POSIX.h"
#endif
namespace Poco {
class Foundation_API Semaphore: private SemaphoreImpl
/// A Semaphore is a synchronization object with the following
/// characteristics:
/// A semaphore has a value that is constrained to be a non-negative
/// integer and two atomic operations. The allowable operations are V
/// (here called set()) and P (here called wait()). A V (set()) operation
/// increases the value of the semaphore by one.
/// A P (wait()) operation decreases the value of the semaphore by one,
/// provided that can be done without violating the constraint that the
/// value be non-negative. A P (wait()) operation that is initiated when
/// the value of the semaphore is 0 suspends the calling thread.
/// The calling thread may continue when the value becomes positive again.
{
public:
Semaphore(int n);
Semaphore(int n, int max);
/// Creates the semaphore. The current value
/// of the semaphore is given in n. The
/// maximum value of the semaphore is given
/// in max.
/// If only n is given, it must be greater than
/// zero.
/// If both n and max are given, max must be
/// greater than zero, n must be greater than
/// or equal to zero and less than or equal
/// to max.
~Semaphore();
/// Destroys the semaphore.
void set();
/// Increments the semaphore's value by one and
/// thus signals the semaphore. Another thread
/// waiting for the semaphore will be able
/// to continue.
void wait();
/// Waits for the semaphore to become signalled.
/// To become signalled, a semaphore's value must
/// be greater than zero.
/// Decrements the semaphore's value by one.
void wait(long milliseconds);
/// Waits for the semaphore to become signalled.
/// To become signalled, a semaphore's value must
/// be greater than zero.
/// Throws a TimeoutException if the semaphore
/// does not become signalled within the specified
/// time interval.
/// Decrements the semaphore's value by one
/// if successful.
bool tryWait(long milliseconds);
/// Waits for the semaphore to become signalled.
/// To become signalled, a semaphore's value must
/// be greater than zero.
/// Returns true if the semaphore
/// became signalled within the specified
/// time interval, false otherwise.
/// Decrements the semaphore's value by one
/// if successful.
private:
Semaphore();
Semaphore(const Semaphore&);
Semaphore& operator = (const Semaphore&);
};
//
// inlines
//
inline void Semaphore::set()
{
setImpl();
}
inline void Semaphore::wait()
{
waitImpl();
}
inline void Semaphore::wait(long milliseconds)
{
if (!waitImpl(milliseconds))
throw TimeoutException();
}
inline bool Semaphore::tryWait(long milliseconds)
{
return waitImpl(milliseconds);
}
} // namespace Poco
#endif // Foundation_Semaphore_INCLUDED
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