gw-semaphore.c

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/* ==================================================================== 
 * The Kannel Software License, Version 1.0 
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 * Portions of this software are based upon software originally written at  
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 */ 

/*
 * semaphore.c - implementation of semaphores
 *
 * Lars Wirzenius
 * Alexander Malysh <a.malysh@centrium.de>, 2004
 */


#include "gwlib/gwlib.h"

#ifdef HAVE_SEMAPHORE
#include <semaphore.h>
#include <errno.h>
#endif

struct Semaphore {
#ifdef HAVE_SEMAPHORE
    sem_t sem;
#else
    List *list;
#endif
};


Semaphore *semaphore_create(long n)
{
    Semaphore *semaphore;
#ifndef HAVE_SEMAPHORE
    static char item;
#endif
    
    semaphore = gw_malloc(sizeof(*semaphore));

#ifdef HAVE_SEMAPHORE
    if (sem_init(&semaphore->sem, 0, (unsigned int) n) != 0)
        panic(errno, "Could not initialize semaphore.");
#else
    semaphore->list = gwlist_create();
    gwlist_add_producer(semaphore->list);
    while (n-- > 0)
    gwlist_produce(semaphore->list, &item);
#endif

    return semaphore;
}


void semaphore_destroy(Semaphore *semaphore)
{
    if (semaphore != NULL) {
#ifdef HAVE_SEMAPHORE
        if (sem_destroy(&semaphore->sem) != 0)
            panic(errno, "Destroying semaphore while some threads are waiting.");
#else
    gwlist_destroy(semaphore->list, NULL);
#endif
    gw_free(semaphore);
    }
}


void semaphore_up(Semaphore *semaphore)
{
#ifndef HAVE_SEMAPHORE
    static char item;
    gw_assert(semaphore != NULL);
    gwlist_produce(semaphore->list, &item);
#else
    gw_assert(semaphore != NULL);
    if (sem_post(&semaphore->sem) != 0)
        error(errno, "Value for semaphore is out of range.");
#endif
}


void semaphore_down(Semaphore *semaphore)
{
    gw_assert(semaphore != NULL);
#ifdef HAVE_SEMAPHORE
    sem_wait(&semaphore->sem);
#else
    gwlist_consume(semaphore->list);
#endif
}


long semaphore_getvalue(Semaphore *semaphore)
{
    gw_assert(semaphore != NULL);
#ifdef HAVE_SEMAPHORE
    {
        int val;
        if (sem_getvalue(&semaphore->sem, &val) != 0)
            panic(errno, "Could not get semaphore value.");
        return val;
    }
#else
    return gwlist_len(semaphore->list);
#endif
}