//
// 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/Exception.h"
#include "Poco/Foundation.h"


#    include "Poco/Semaphore_POSIX.h"


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