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sem.c
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sem.c
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/* Routines for hanling mmap data and semaphores */
#include "defs.h"
#include "ext.h"
static int semid[7] = {-1, -1, -1, -1, -1, -1, -1};
int8_t msem_init(int32_t *sem, int32_t val) {
*sem = val;
return 1;
}
/* lock a semaphore */
int32_t msem_lock(int32_t *which) {
struct sembuf lock[2];
if (semid[*which] < 0) {
/* 1000 + which makes for an easy semkey. Easy to change, too */
if ((semid[*which] = semget(1000 + *which, 1, IPC_CREAT | 0664)) < 0) {
perror("semget");
return -1;
}
}
lock[0].sem_num = 0;
lock[0].sem_op = 0;
lock[0].sem_flg = 0;
lock[1].sem_num = 0;
lock[1].sem_op = 1; /* inc by 1 */
lock[1].sem_flg = SEM_UNDO;
if (semop(semid[*which], &lock[0], 2) < 0) {
return -1;
}
return 0;
}
/* unlock */
int32_t msem_unlock(int32_t *which) {
struct sembuf unlock;
unlock.sem_num = 0;
unlock.sem_op = -1;
unlock.sem_flg = SEM_UNDO | IPC_NOWAIT;
if (semop(semid[*which], &unlock, 1) < 0) {
return -1;
}
return 0;
}