进程间通信之信号量--使用信号实现生产者消费者问题
生产者消费者是数学中的一个经典的问题，也是编程中的一个经典问题。
本示例采用信号量来解决这个问题，其实，最终也就是进程之间同步的问题。
生产者源代码如下：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/stat.h>
#include <sys/sem.h>
int sem_id;
void init()
{
key_t key;
int ret;
unsigned short sem_array[2]; //0代表生产者，1代表消费者
union semun
{
int val;
struct semid_ds *buf;
unsigned short *array;
}arg;
key=ftok(".",'s');
sem_id=semget(key,2,0777|IPC_CREAT);
sem_array[0]=0;
sem_array[1]=100;
arg.array=sem_array;
ret=semctl(sem_id,0,SETALL,arg);
if(ret==-1)
{
perror("semctl");
exit(1);
}
printf("productor init is %d\n",semctl(sem_id,0,GETVAL));
printf("consumer init is %d\n",semctl(sem_id,1,GETVAL));
}
void del()
{
semctl(sem_id,IPC_RMID,0);
}
int main()
{
struct sembuf sops[2];
int retv;
sops[0].sem_num= 0;
sops[0].sem_op = 1;
sops[0].sem_flg = 0;
sops[1].sem_num= 1;
sops[1].sem_op = -1;
sops[1].sem_flg = 0;
init();
printf("this is productor\n");
while(1)
{
printf("\n\nbefore produce\n");
printf("productor number is %d\n",semctl(sem_id,0,GETVAL));
printf("space number is %d\n",semctl(sem_id,1,GETVAL));
retv=semop(sem_id,&sops[1],1);
//if(retv==-1)
printf("no work semo on sops[0] retv%d\n",retv);
printf("now producting....\n");
retv=semop(sem_id,&sops[0],1);
//if(retv==-1)
printf("no work semo on sops[0] retv=%d\n",retv);
printf("\nafter produce\n");
printf("productor number is %d\n",semctl(sem_id,0,GETVAL));
printf("space number is %d\n",semctl(sem_id,1,GETVAL));
sleep(1);
}
del();
return 0;
}
消费者源代码如下：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/stat.h>
#include <sys/sem.h>
int sem_id;
void init()
{
key_t key;
key=ftok(".",'s');
sem_id=semget(key,2,0777|IPC_CREAT);
}
int main()
{
struct sembuf sops[2];
sops[0].sem_num= 0;
sops[0].sem_op = -1;
sops[0].sem_flg = 0;
sops[1].sem_num= 1;
sops[1].sem_op = 1;
sops[1].sem_flg = 0;
init();
printf("this is customer\n");
while(1)
{
printf("\n\nbefore consumer\n");
printf("productor number is %d\n",semctl(sem_id,0,GETVAL));
printf("space number is %d\n",semctl(sem_id,1,GETVAL));
semop(sem_id,&sops[0],1);
printf("now consuming....\n");
semop(sem_id,&sops[1],1);
printf("\nafter consume\n");
printf("productor number is %d\n",semctl(sem_id,0,GETVAL));
printf("space number is %d\n",semctl(sem_id,1,GETVAL));
sleep(3);
}
return 0;
}