server.c

Linux大学上机源码学习

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <stdio.h>
#include <string.h>
union semun{
  int val;
  struct semid_ds *buf;
  unsigned short *array;
};
 int open_semaphore_set(int keyval,int numsems)
   { int sid;
     sid=semget(keyval,numsems,IPC_CREAT|0666);
     return sid;
  }
int get_sem_val(int sid,int semnum)
{ return(semctl(sid,semnum,GETVAL,0));}

void init_a_semaphore(int sid,int semnum,int initval)
{ union semun semopts;
  semopts.val=initval;
  semctl(sid,semnum,SETVAL,semopts);
}

/*void init_all_semaphore(int sid,int val_array[])
{ union semun semopts;
  semopts.array=val_array;
  semctl(sid,0,SETALL,semopts);

}
*/
int changemode(int sid,char *mode)
{ int rc;
  union semun semopts;
  struct semid_ds mysemds;
  semopts.buf=&mysemds;
  if((rc=semctl(sid,0,IPC_STAT,semopts))==-1)
     return -1;
  sscanf(mode,"%o",&semopts.buf->sem_perm.mode);
  return(semctl(sid,0,IPC_SET,semopts));
 }

int rm_semaphore(int sid)
{ return(semctl(sid,0,IPC_RMID,0));
}

int semaphore_P(int sem_id)
{ struct sembuf sb;
  sb.sem_num=0;
  sb.sem_op=-1;
  sb.sem_flg=SEM_UNDO;
  semop(sem_id,&sb,1);
  return 1;
}

int semaphore_V(int sem_id)
{ struct sembuf sb;
  sb.sem_num=0;
  sb.sem_op=1;
  sb.sem_flg=SEM_UNDO;
  semop(sem_id,&sb,1);
  return 1;
}
main()
{
struct exchange{
    char buf[BUFSIZ+80];
    int seq;
 }*shm;
 int shmid;
 unsigned char *retval;
 int producer,consumer,i;
 consumer=open_semaphore_set(1234,1);
 init_a_semaphore(consumer,0,1);
 producer=open_semaphore_set(4321,1);
 init_a_semaphore(producer,0,0);
 shmid=shmget(5678,sizeof(struct exchange),0666|IPC_CREAT);
 retval=shmat(shmid,(unsigned char *)0,0);
 shm=(struct exchange *)retval;
 for(i=0;;i++){
   semaphore_P(producer);
   printf("data receive:%s,sequence:%d\n",shm->buf,shm->seq);
   semaphore_V(consumer);
   if(strncmp(shm->buf,"end",3)==0)
       break;
}
rm_semaphore(producer);
rm_semaphore(consumer);
shmctl(shmid,IPC_RMID,0);
exit(0);
}