生产者消费者问题（Linux）

C实现

#include 
#include 
#include 
#include 
#include 
#include 
#define NEED_P 2
#define NEED_C 3
#define WORKS_P 6
#define WORKS_C 4
#define BUF_LENGTH (sizeof(struct mybuffer))
#define LETTER_NUM 3
#define SHM_MODE 0600
#define SEM_ALL_KEY 1234
#define SEM_EMPTY 0
#define SEM_FULL 1
//缓冲区结构（循环队列）
struct mybuffer
{
      char letter[LETTER_NUM];
      int head;
      int tail;
      int is_empty;
};
//得到5以内的一个随机数
int get_random()
{
      int t;
      srand((unsigned)(getpid() + time(NULL)));
      t = rand() % 5;
      return t;
}
//得到A~Z的一个随机字母
char get_letter()
{
      char a;
      srand((unsigned)(getpid() + time(NULL)));
      a = (char)((char)(rand() % 26) + 'A');
      return a;
}
//P操作
void p(int sem_id, int sem_num)
{
      struct sembuf xx;
      xx.sem_num = sem_num;
      xx.sem_op = - 1;
      xx.sem_flg = 0;
      semop(sem_id, & xx, 1);
}
//V操作
void v(int sem_id, int sem_num)
{
      struct sembuf xx;
      xx.sem_num = sem_num;
      xx.sem_op = 1;
      xx.sem_flg = 0;
      semop(sem_id, & xx, 1);
}
//主函数
int main(int argc, char *argv[])
{
      int i, j;
      int shm_id, sem_id;
      int num_p = 0, num_c = 0;
      struct mybuffer *shmptr;
      char lt;
      time_t now;
      pid_t pid_p, pid_c;
      
    sem_id = semget(SEM_ALL_KEY, 2, IPC_CREAT | 0660);
      if (sem_id >= 0)
    
  {
            printf("主进程开始，信号量创建完毕\n");
        
  }
      semctl(sem_id, SEM_EMPTY, SETVAL, LETTER_NUM);
      semctl(sem_id, SEM_FULL, SETVAL, 0);
      
    if ((shm_id = shmget(IPC_PRIVATE, BUF_LENGTH, SHM_MODE)) < 0)
    
  {
            printf("Error on shmget.\n");
            exit(1);
        
  }
      if ((shmptr = shmat(shm_id, 0, 0)) == (void *)-1)
    
  {
            printf("Error on shmat.\n");
            exit(1);
        
  }
      shmptr->head = 0;
      shmptr->tail = 0;
      shmptr->is_empty = 1;
      
    while ((num_p++) < NEED_P)
    
  {
            if ((pid_p = fork()) < 0)
        
    {
                  printf("Error on fork.\n");
                  exit(1);
              
    }
             //如果是子进程，开始创建生产者
        if (pid_p == 0)
        
    {
                  if ((shmptr = shmat(shm_id, 0, 0)) == (void *)-1)
            
      {
                        printf("Error on shmat.\n");
                        exit(1);
                    
      }
                  for (i = 0; i < WORKS_P; i++)
            
      {
                        p(sem_id, SEM_EMPTY);
                        sleep(get_random());
                        shmptr->letter[shmptr->tail] = lt = get_letter();
                        shmptr->tail = (shmptr->tail + 1) % LETTER_NUM;
                        shmptr->is_empty = 0;
                        now = time(NULL);
                        printf("当前时间 %02d:%02d:%02d\t", localtime(&now)->tm_hour, localtime(&now)->tm_min, localtime(&now)->tm_sec);
            printf("生产者 %d 放入 '%c'\t当前缓冲区：", num_p, lt);
                        for (j = (shmptr->tail - 1 >= shmptr->head) ? (shmptr->tail - 1) : (shmptr->tail - 1 + LETTER_NUM); !(shmptr->is_empty) && j >= shmptr->head; j--)
                
        {
                              printf("%c", shmptr->letter[j % LETTER_NUM]);
                          
        }
            printf("\n");
                        fflush(stdout);
                        v(sem_id, SEM_FULL);
                    
      }
                  shmdt(shmptr);
                  exit(0);
              
    }
        
  }
      while (num_c++ < NEED_C)
    
  {
            if ((pid_c = fork()) < 0)
        
    {
                  printf("Error on fork.\n");
                  exit(1);
              
    }
             //如果是子进程，开始创建消费者
        if (pid_c == 0)
        
    {
                  if ((shmptr = shmat(shm_id, 0, 0)) == (void *)-1)
            
      {
                        printf("Error on shmat.\n");
                        exit(1);
                    
      }
                  for (i = 0; i < WORKS_C; i++)
            
      {
                        p(sem_id, SEM_FULL);
                        sleep(get_random());
                        lt = shmptr->letter[shmptr->head];
                        shmptr->head = (shmptr->head + 1) % LETTER_NUM;
                        shmptr->is_empty = (shmptr->head == shmptr->tail);
                        now = time(NULL);
                        printf("当前时间 %02d:%02d:%02d\t", localtime(&now)->tm_hour, localtime(&now)->tm_min, localtime(&now)->tm_sec);
             printf("消费者 %d 拿走 '%c'\t当前缓冲区：", num_c, lt);
                        for (j = (shmptr->tail - 1 >= shmptr->head) ? (shmptr->tail - 1) : (shmptr->tail - 1 + LETTER_NUM); !(shmptr->is_empty) && j >= shmptr->head; j--)
                
        {
                              printf("%c", shmptr->letter[j % LETTER_NUM]);
                          
        }
                        printf("\n");
                        fflush(stdout);
                        v(sem_id, SEM_EMPTY);
                    
      }
                  shmdt(shmptr);
                  exit(0);
              
    }
        
  }
      
     //主控程序最后退出
    while (wait(0) != - 1);
      shmdt(shmptr);
      shmctl(shm_id, IPC_RMID, 0);
      semctl(sem_id, IPC_RMID, 0);
      printf("主程序完成\n");
      fflush(stdout);
      exit(0);
}