ipc.c

抽烟者问题。假设一个系统中有三个抽烟者进程

#include"ipc.h"
//定义有关函数

int get_ipc_id(char *proc_file,key_t key){
  FILE *pf;
  int i,j;
  char line[BUFSZ],colum[BUFSZ];

  if((pf=fopen(proc_file,"r"))==NULL){
      perror("Proc file not open");
      exit(EXIT_FAILURE);
       }
   fgets(line,BUFSZ,pf);
   while(!feof(pf)){
       i=j=0;
       fgets(line,BUFSZ,pf);
       while(line[i]==' ')i++;
       while(line[i]!=' ')colum[j++]=line[i++];
       colum[j]='\0';
       if(atoi(colum)!=key)continue;
       j=0;
       while(line[i]==' ')i++;
       while(line[i]!=' ')colum[j++]=line[i++];
       colum[j]='\0';
       i=atoi(colum);
       fclose(pf);
       return i;
      }
      fclose(pf);
      return -1;
  }

int down(int sem_id){
struct sembuf buf;
buf.sem_op=-1;
buf.sem_num=0;
buf.sem_flg=SEM_UNDO;
if((semop(sem_id,&buf,1))<0){
     perror("down error");
     exit(EXIT_FAILURE);
    }
return EXIT_SUCCESS;
}


int up(int sem_id){
    struct sembuf buf;
    buf.sem_op=1;
    buf.sem_num=0;
    buf.sem_flg=SEM_UNDO;
    if((semop(sem_id,&buf,1))<0){
        perror("up error");
        exit(EXIT_FAILURE);
       }
return EXIT_SUCCESS;
  }

int set_sem(key_t sem_key,int sem_val,int sem_flg){
    int sem_id;
    Sem_uns sem_arg;

    if((sem_id=get_ipc_id("/proc/sysvipc/sem",sem_key))<0)
     {
        if((sem_id=semget(sem_key,1,sem_flg))<0)
            {
               perror("semaphore create error");
               exit(EXIT_FAILURE);
              }
            sem_arg.val=sem_val;
            if(semctl(sem_id,0,SETVAL,sem_arg)<0){
               perror("semaphore set error");
               exit(EXIT_FAILURE);
               }
           }
   return sem_id;
  }



  char *set_shm(key_t shm_key,int shm_num,int shm_flg){
     int i,shm_id;
     char *shm_buf;

      if((shm_id=get_ipc_id("/proc/sysvipc/shm",shm_key))<0){
          if((shm_id=shmget(shm_key,shm_num,shm_flg))<0){
              perror("shareMemory set error");
              exit(EXIT_FAILURE);
             }
          if((shm_buf=(char*)shmat(shm_id,0,0))<(char*)0){
              perror("get shareMemory error");
              exit(EXIT_FAILURE);
              }
           for(i=0;i<shm_num;i++)shm_buf[i]=0;
              }

      if((shm_buf=(char*)shmat(shm_id,0,0))<(char*)0){
          perror("get shareMemory error");
          exit(EXIT_FAILURE);
          }
       return shm_buf;
   }


  int set_msq(key_t msq_key,int msq_flg){
       int msq_id;
       
       if((msq_id=get_ipc_id("/proc/sysvipc/msg",msq_key))<0){
           if((msq_id=msgget(msq_key,msq_flg))<0){
               perror("messageQueue set error");
               exit(EXIT_FAILURE);
               }
          }
       return msq_id;
 }