風行草偃

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生产者消费者问题(Linux)

#include <stdio.h>

#include <time.h>

#include <unistd.h>

#include <sys/ipc.h>

#include <sys/shm.h>

#include <sys/sem.h>

#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);

}


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