MobiCoreDriverLib/Common/CSemaphore.cpp

/** @addtogroup MCD_MCDIMPL_DAEMON_SRV
 * @{
 * @file
 *
 * Semaphore implementation (pthread wrapper).
 *
 * Copyright (c) 2013 TRUSTONIC LIMITED
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the TRUSTONIC LIMITED nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#include <time.h>
#include <limits.h>
#include "CSemaphore.h"
#include <stdio.h>

//------------------------------------------------------------------------------
CSemaphore::CSemaphore(int size) : m_waiters_count(0), m_count(size)
{
    pthread_mutex_init(&m_mutex, NULL);
    pthread_cond_init(&m_cond, NULL);
}


//------------------------------------------------------------------------------
CSemaphore::~CSemaphore()
{
    pthread_mutex_destroy(&m_mutex);
    pthread_cond_destroy(&m_cond);
}


//------------------------------------------------------------------------------
void CSemaphore::wait()
{
    pthread_mutex_lock(&m_mutex);
    m_waiters_count ++;
    while ( m_count == 0 )
        pthread_cond_wait(&m_cond, &m_mutex);
    m_waiters_count --;
    m_count --;
    pthread_mutex_unlock(&m_mutex);
}

//------------------------------------------------------------------------------
bool CSemaphore::wait(int sec)
{
    int rc = 0;
    struct timespec tm;
    if (sec < 0)
        sec = LONG_MAX;
    clock_gettime(CLOCK_REALTIME, &tm);
    tm.tv_sec += sec;

    pthread_mutex_lock(&m_mutex);
    m_waiters_count ++;
    if ( m_count == 0 ) {
        rc = pthread_cond_timedwait(&m_cond, &m_mutex, &tm);
    }
    m_waiters_count --;
    // Decrement only if waiting actually succeeded, otherwise we
    // just timed out
    if (!rc)
        m_count --;
    pthread_mutex_unlock(&m_mutex);
    return (rc == 0);
}


//------------------------------------------------------------------------------
bool CSemaphore::wouldWait()
{
    bool ret = false;
    pthread_mutex_lock(&m_mutex);
    if ( m_count == 0 )
        ret = true;
    pthread_mutex_unlock(&m_mutex);
    return ret;
}


//------------------------------------------------------------------------------
void CSemaphore::signal()
{
    pthread_mutex_lock(&m_mutex);
    if ( m_waiters_count > 0 )
        pthread_cond_signal(&m_cond);
    m_count ++;
    pthread_mutex_unlock(&m_mutex);
}

/** @} */