/*
 * Copyright (C) 2007-2019 Xagasoft, All rights reserved.
 *
 * This file is part of the libbu++ library and is released under the
 * terms of the license contained in the file LICENSE.
 */

#ifndef BU_CONDITION_H
#define BU_CONDITION_H

#include <pthread.h>

#include "bu/mutex.h"

namespace Bu
{
    /**
     * Ito condition.  This is a fairly simple condition mechanism.  As you may
     * notice this class inherits from the Mutex class, this is because all
     * conditions must be within a locked block.  The standard usage of a
     * condition is to pause one thread, perhaps indefinately, until another
     * thread signals that it is alright to procede.
     * <br>
     * Standard usage for the thread that wants to wait is as follows:
     * <pre>
     * Condition cond;
     * ... // Perform setup and enter your run loop
     * cond.lock();
     * while( !isFinished() ) // Could be anything you're waiting for
     *     cond.wait();
     * ...  // Take care of what you have to.
     * cond.unlock();
     * </pre>
     * The usage for the triggering thread is much simpler, when it needs to
     * tell the others that it's time to grab some data it calls either signal
     * or broadcast.  See both of those functions for the difference.
     *@ingroup Threading
     */
    class Condition : public Mutex
    {
    public:
        /**
         * Create a condition.
         */
        Condition();

        /**
         * Destroy a condition.
         */
        ~Condition();

        /**
         * Wait forever, or until signalled.  This has to be called from within
         * a locked section, i.e. before calling this this object's lock
         * function should be called.
         */
        int wait();

        /**
         * Wait for a maximum of nSec seconds and nUSec micro-seconds or until
         * signalled.  This is a little more friendly function if you want to
         * perform other operations in the thrad loop that calls this function.
         * Like the other wait function, this must be inside a locked section.
         *@param nSec The seconds to wait.
         *@param nUSec the micro-seconds to wait.
         */
        int wait( int nSec, int nUSec );

        /**
         * Notify the next thread waiting on this condition that they can go
         * ahead.  This only signals one thread, the next one in the condition
         * queue, that it is safe to procede with whatever operation was being
         * waited on.
         */
        int signal();

        /**
         * Notify all threads waiting on this condition that they can go ahead
         * now. This function is slower than signal, but more effective in
         * certain situations where you may not know how many threads should be
         * activated.
         */
        int broadcast();

    private:
        pthread_cond_t cond;    /**< Internal condition reference. */
    };
}

#endif