l3.libnazgul/src/queueReadTryLock.c

#include "libnazgul.h"
#include "ids.h"

#define DEBUG 0

int msgQueueReadTryLock(msgSpaceId externId, int queueIdx)
{
	int semval;
	sem_t *queueSemFd;
	msgQueueSemId queueSemId;

	msgQueueReadSemIdIntern(queueSemId, externId, queueIdx);
	queueSemFd = sem_open(queueSemId, O_CREAT, SEM_DEFAULT_MODE, 1);
	if (queueSemFd == SEM_FAILED) {
		NZG_ERROR("sem_open", queueSemId);
		goto ERROR;
	}

	if (sem_trywait(queueSemFd) == -1) {
		NZG_ERROR("sem_wait", queueSemId);
		goto ERROR;
	}
	if (DEBUG) {
		printf("Locking %s\n", queueSemId);
	}
	semval = 0;
	sem_getvalue(queueSemFd, &semval);
	if (DEBUG) {
		printf("(AfterValue:%d)\n", semval);
	}

	sem_close(queueSemFd);

	return 0;
 ERROR:
	return -1;
}