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[<<Previous Entry] [^^Up^^] [Next Entry>>] [Menu] [About The Guide] Производитель и Потребитель буфера ПРОИЗВОДИТЕЛЬ БУФЕРА, prod_onebuf.c : /* producer program: producer program sets up a buffer to be read by a consumer semaphores are used to ensure that producer doesn't overwrite an unread buffer and consumer doesn't the same data more than once. */ #include <sys/types.h> #include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <sys/ipc.h> #include <sys/sem.h> #include <sys/shm.h> #define MSG_SIZE 30 #define MAX 5 main() { key_t key; /* two semaphores in a set index 0 -incremented when producer has reset buffer -tested and decremented by consumer to check if buffer has been reset index 1 -incremented when consumer has read buffer -tested and decremented by producer to check if consumer is done */ static struct sembuf wait_consumed = { 1, -1, 0}; static struct sembuf signal_produced = { 0, 1, 0}; int semid, shmid, i; char *message; if((key = ftok( getenv("HOME"), 'u')) == -1){ fprintf(stderr,"ftok key formation error\n"); exit(1); } if((semid=semget(key, 2, IPC_CREAT | 0660)) == -1){ perror("producer semget():"); exit(2); } if((shmid=shmget(key, MSG_SIZE, IPC_CREAT | 0660)) == -1) { perror("producer shmget():"); exit(3); } message=shmat(shmid, 0, 0); for(i=1; i < MAX; i++) { /* producer has to go first */ if(i > 1) semop(semid,&wait_consumed,1); sprintf(message, "message %d", i); semop(semid, &signal_produced, 1); } shmdt(message); sleep(5); /* allow consumer to digest last message */ /* alternatively a DELIMITER string could be placed in shared memory when seen by the consumer, it would exit. the producer would do shmctl(...,IPC_STAT,...) and when shm_attach==1 it would remove the two IPC facilities */ shmctl(shmid, IPC_RMID, NULL); semctl(semid, 0, IPC_RMID ,0); } NОТРЕБИТЕЛЬ БУФЕРА, cons_onebuf.c : /* consumer program: producer program sets up a buffer to be read by a consumer. semaphores are used to ensure that producer doesn't overwrite an unread buffer and consumer doesn't read the same data more than once. */ #include <sys/types.h> #include <stdio.h> #include <stdlib.h> #include <sys/ipc.h> #include <sys/sem.h> #include <sys/shm.h> #define MSG_SIZE 30 main(int argc, char *argv[]) { key_t key; /* two semaphores in a set index 0 - incremented when producer has reset buffer - tested and decremented by consumer to check if buffer has been reset index 1 - incremented when consumer has read buffer - tested and decremented by producer to check if consumer is done */ static struct sembuf wait_produced = { 0, -1, 0}; static struct sembuf signal_consumed = { 1, 1, 0}; int semid, shmid, rtn; char *message; if((key = ftok( getenv("HOME"), 'u')) == -1){ fprintf(stderr,"ftok key formation error\n"); exit(1); } /* either producer or consumer might be the creator but producer will be the remover of the IPC resources. producer and consumer's effective uid must be the same. */ if ((semid=semget(key, 2, IPC_CREAT | 0660)) == -1) { perror("consumer semget():"); exit(2); } if ((shmid=shmget(key, MSG_SIZE, IPC_CREAT | 0660)) == -1) { perror("producer shmget():"); exit(3); } message=shmat(shmid, (char *)0, SHM_RDONLY); while(1){ rtn=semop(semid,&wait_produced,1); /* when producer is done semid will be IPC_RMID forcing break */ if(rtn == -1){ perror("consumer - semop on wait_consumed"); break; } printf("%s received: %s\n", argv[0], message); semop(semid, &signal_consumed, 1); } shmdt(message); exit(0); } ВЫЗОВ: $ prod_onebuf& 14649 $ cons_onebuf cons_onebuf received: message 1 cons_onebuf received: message 2 cons_onebuf received: message 3 cons_onebuf received: message 4 consumer-semop on wait_consumed:Identifier removed |