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+/****************************************************************************
+**
+** TQSemaphore class for Unix
+**
+** Created : 20010725
+**
+** Copyright (C) 1992-2008 Trolltech ASA.  All rights reserved.
+**
+** This file is part of the tools module of the TQt GUI Toolkit.
+**
+** This file may be used under the terms of the GNU General
+** Public License versions 2.0 or 3.0 as published by the Free
+** Software Foundation and appearing in the files LICENSE.GPL2
+** and LICENSE.GPL3 included in the packaging of this file.
+** Alternatively you may (at your option) use any later version
+** of the GNU General Public License if such license has been
+** publicly approved by Trolltech ASA (or its successors, if any)
+** and the KDE Free TQt Foundation.
+**
+** Please review the following information to ensure GNU General
+** Public Licensing requirements will be met:
+** http://trolltech.com/products/qt/licenses/licensing/opensource/.
+** If you are unsure which license is appropriate for your use, please
+** review the following information:
+** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
+** or contact the sales department at sales@trolltech.com.
+**
+** This file may be used under the terms of the Q Public License as
+** defined by Trolltech ASA and appearing in the file LICENSE.TQPL
+** included in the packaging of this file.  Licensees holding valid TQt
+** Commercial licenses may use this file in accordance with the TQt
+** Commercial License Agreement provided with the Software.
+**
+** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
+** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
+** herein.
+**
+**********************************************************************/
+
+#if defined(TQT_THREAD_SUPPORT)
+
+#include "tqsemaphore.h"
+#include "tqmutex.h"
+#include "tqwaitcondition.h"
+
+
+/*!
+    \class TQSemaphore tqsemaphore.h
+    \threadsafe
+    \brief The TQSemaphore class provides a robust integer semaphore.
+
+    \ingroup thread
+    \ingroup environment
+
+    A TQSemaphore can be used to serialize thread execution, in a
+    similar way to a TQMutex. A semaphore differs from a mutex, in
+    that a semaphore can be accessed by more than one thread at a
+    time.
+
+    For example, suppose we have an application that stores data in a
+    large tree structure. The application creates 10 threads
+    (commonly called a thread pool) to perform searches on the tree.
+    When the application searches the tree for some piece of data, it
+    uses one thread per base node to do the searching. A semaphore
+    could be used to make sure that two threads don't try to search
+    the same branch of the tree at the same time.
+
+    A non-computing example of a semaphore would be dining at a
+    restuarant. A semaphore is initialized to have a maximum count
+    equal to the number of chairs in the restuarant. As people
+    arrive, they want a seat. As seats are filled, the semaphore is
+    accessed, once per person. As people leave, the access is
+    released, allowing more people to enter. If a party of 10 people
+    want to be seated, but there are only 9 seats, those 10 people
+    will wait, but a party of 4 people would be seated (taking the
+    available seats to 5, making the party of 10 people wait longer).
+
+    When a semaphore is created it is given a number which is the
+    maximum number of concurrent accesses it will permit. Accesses to
+    the sempahore are gained using operator++() or operator+=(), and
+    released with operator--() or operator-=(). The number of
+    accesses allowed is retrieved with available(), and the total
+    number with total(). Note that the incrementing functions will
+    block if there aren't enough available accesses. Use tryAccess()
+    if you want to acquire accesses without blocking.
+*/
+
+
+class TQSemaphorePrivate {
+public:
+    TQSemaphorePrivate(int);
+
+    TQMutex mutex;
+    TQWaitCondition cond;
+
+    int value, max;
+};
+
+
+TQSemaphorePrivate::TQSemaphorePrivate(int m)
+    : mutex(FALSE), value(0), max(m)
+{
+}
+
+
+/*!
+    Creates a new semaphore. The semaphore can be concurrently
+    accessed at most \a maxcount times.
+*/
+TQSemaphore::TQSemaphore(int maxcount)
+{
+    d = new TQSemaphorePrivate(maxcount);
+}
+
+
+/*!
+    Destroys the semaphore.
+
+    \warning If you destroy a semaphore that has accesses in use the
+    resultant behavior is undefined.
+*/
+TQSemaphore::~TQSemaphore()
+{
+    delete d;
+}
+
+
+/*!
+    Postfix ++ operator.
+
+    Try to get access to the semaphore. If \l available() == 0, this
+    call will block until it can get access, i.e. until available() \>
+    0.
+*/
+int TQSemaphore::operator++(int)
+{
+    TQMutexLocker locker(&d->mutex);
+    while (d->value >= d->max)
+	d->cond.wait(locker.mutex());
+
+    ++d->value;
+    if (d->value > d->max)
+	d->value = d->max;
+
+    return d->value;
+}
+
+
+/*!
+    Postfix -- operator.
+
+    Release access of the semaphore. This wakes all threads waiting
+    for access to the semaphore.
+*/
+int TQSemaphore::operator--(int)
+{
+    TQMutexLocker locker(&d->mutex);
+
+    --d->value;
+    if (d->value < 0)
+	d->value = 0;
+
+    d->cond.wakeAll();
+
+    return d->value;
+}
+
+
+/*!
+    Try to get access to the semaphore. If \l available() \< \a n, this
+    call will block until it can get all the accesses it wants, i.e.
+    until available() \>= \a n.
+*/
+int TQSemaphore::operator+=(int n)
+{
+    TQMutexLocker locker(&d->mutex);
+
+    if ( n < 0 || n > d->max ) {
+#ifdef QT_CHECK_RANGE
+	tqWarning( "TQSemaphore::operator+=: paramter %d out of range", n );
+#endif // QT_CHECK_RANGE
+	n = n < 0 ? 0 : d->max;
+    }
+
+    while (d->value + n > d->max)
+	d->cond.wait(locker.mutex());
+
+    d->value += n;
+
+    return d->value;
+}
+
+
+/*!
+    Release \a n accesses to the semaphore.
+*/
+int TQSemaphore::operator-=(int n)
+{
+    TQMutexLocker locker(&d->mutex);
+
+    if ( n < 0 || n > d->value ) {
+#ifdef QT_CHECK_RANGE
+	tqWarning( "TQSemaphore::operator-=: paramter %d out of range", n );
+#endif // QT_CHECK_RANGE
+	n = n < 0 ? 0 : d->value;
+    }
+
+    d->value -= n;
+    d->cond.wakeAll();
+
+    return d->value;
+}
+
+
+/*!
+    Returns the number of accesses currently available to the
+    semaphore.
+*/
+int TQSemaphore::available() const
+{
+    TQMutexLocker locker(&d->mutex);
+    return d->max - d->value;
+}
+
+
+/*!
+    Returns the total number of accesses to the semaphore.
+*/
+int TQSemaphore::total() const
+{
+    TQMutexLocker locker(&d->mutex);
+    return d->max;
+}
+
+
+/*!
+    Try to get access to the semaphore. If \l available() \< \a n, this
+    function will return FALSE immediately. If \l available() \>= \a n,
+    this function will take \a n accesses and return TRUE. This
+    function does \e not block.
+*/
+bool TQSemaphore::tryAccess(int n)
+{
+    TQMutexLocker locker(&d->mutex);
+
+    if (d->value + n > d->max)
+	return FALSE;
+
+    d->value += n;
+
+    return TRUE;
+}
+
+#endif // TQT_THREAD_SUPPORT