136 lines
2.4 KiB
C
136 lines
2.4 KiB
C
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#include <sys/types.h>
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#include <sys/ipc.h>
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#include <sys/sem.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <errno.h>
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union semun
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{
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int val;
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struct semid_ds *buf;
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ushort *array;
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};
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void erreur(char *s)
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{
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if(errno)
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perror(s);
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else
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fprintf(stderr,"%s\n",s);
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exit(1);
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}
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/*-----------------------------------------------------------*/
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int creat_sem(key_t cle,int val)
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/* creation du semaphore cle ayant comme valeur initiale val
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retourne un identificateur de semaphore >=0 ou -1 si erreur
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*/
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{
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int semid ;
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union semun arg;
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if((semid=semget(cle,1,0666+IPC_CREAT+IPC_EXCL))>= 0)
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{
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arg.val=val;
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if(semctl(semid,0,SETVAL,arg)< 0)
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semid = -1;
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}
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return(semid);
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}
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/*--------------------------------------------------------------*/
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int del_sem(key_t cle)
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/* destruction du semaphore cle
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retourne:
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0 si la destruction du semaphore s est effectuee correctement
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-1 si erreur
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*/
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{
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int semid;
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if((semid = semget(cle,0,0)) >= 0)
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semid = semctl(semid,0,IPC_RMID,0);
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if(semid != -1)
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semid = 0;
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return semid;
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}
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/*---------------------------------------------------------------*/
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int chuid_sem(int semid, uid_t uid)
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/* change le owner's user id du semaphore semid en lui donnant la valeur
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uid
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retourne 0 si ok
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-1 si erreur
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*/
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{
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int ret;
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union semun arg;
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struct semid_ds str_sema;
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arg.buf = &str_sema;
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if((ret = semctl(semid,0,IPC_STAT,arg)) != -1)
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{
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str_sema.sem_perm.uid = uid;
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ret = semctl(semid,0,IPC_SET,arg);
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}
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if(ret != -1)
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ret = 0;
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return ret;
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}
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/*---------------------------------------------------------------*/
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int open_sem(key_t cle)
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/* recherche le semaphore cle
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retourne l'identificateur du semaphore >=0 ou -1 si erreur
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*/
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{
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return(semget(cle,0,0));
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}
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/*----------------------------------------------------------------*/
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void P(int semid)
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{
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struct sembuf psembuf;
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psembuf.sem_op = -1;
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psembuf.sem_flg = 0;
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psembuf.sem_num = 0;
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semop(semid,&psembuf,1);
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}
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/*------------------------------------------------------------------*/
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void V(int semid)
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{
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struct sembuf vsembuf;
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vsembuf.sem_op = 1;
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vsembuf.sem_flg = 0;
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vsembuf.sem_num = 0;
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semop(semid,&vsembuf,1);
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}
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/*--------------------------------------------------------------*/
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