lw-support/src/liblw-support/Thread/Semaphore.cpp

/* lw-support/src/lib/Thread/Semaphore.cpp
 *
 *  (c)2005, Laurence Withers. Released under the GNU GPL. See file
 *  COPYING for more information / terms of license.
*/

namespace lw {



Semaphore::Semaphore(unsigned int init)
    : val(init), waiting(0), err(false)
{
    pthread_mutex_init(&mut, 0);
    pthread_cond_init(&cond, 0);
}



Semaphore::~Semaphore()
{
    signalError();
    while(true) {
        pthread_mutex_lock(&mut);
        if(!waiting) break;
        pthread_mutex_unlock(&mut);
        pthread_yield();
    }
    pthread_mutex_unlock(&mut);

    pthread_mutex_destroy(&mut);
}



void Semaphore::wait(int maxTime)
{
    if(maxTime < 0) {
        wait();
        return;
    }

    // get current time
    struct timeval tv;
    gettimeofday(&tv, 0);

    // compute absolute time
    struct timespec ts;
    ts.tv_sec = tv.tv_sec + (maxTime / 1000);
    ts.tv_nsec = (tv.tv_usec * 1000) + (maxTime % 1000) * tenExp6;
    if(ts.tv_nsec > tenExp9) {
        ++ts.tv_sec;
        ts.tv_nsec -= tenExp9;
    }

    pthread_mutex_lock(&mut);
    ++waiting;

    while(!val && !err) {
        switch(pthread_cond_timedwait(&cond, &mut, &ts)) {
            case ETIMEDOUT: {
                --waiting;
                pthread_mutex_unlock(&mut);
                throw Timeout();
            }

            case 0: break;
        }
    }
    if(err) {
        --waiting;
        pthread_mutex_unlock(&mut);
        throw Error();
    }
    --val;
    --waiting;
    pthread_mutex_unlock(&mut);
}



}