环形队列--单字节

vi in_queue.c (入队)

#include <stdio.h>
#include <stdlib.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>

#define LEN 10

int semid;
struct sembuf p,v;


struct loop_queue {
        int head;
        int tail;
        char mem[LEN];
};

int next(int n) {
        n=(n+1)%LEN;

        return n;
}

int init_queue(struct loop_queue *fifo) {
        fifo->head=0;
        fifo->tail=0;
}

int enqueue(struct loop_queue *fifo,char c) {
        if(fifo->head==next(fifo->tail)) {
                fprintf(stderr,"Queue Full.\n");
                return -1;
        }

        (fifo->mem)[fifo->tail]=c;
        fifo->tail=next(fifo->tail);

        return 0;
}

int dequeue(struct loop_queue *fifo,char *c) {
        if(fifo->head==fifo->tail) {
                printf("Queue Null.\n");
                return -1;
        }

        *c=(fifo->mem)[fifo->head];
        fifo->head=next(fifo->head);

        return 0;
}

int P_op() {
        int ret;

        ret=semop(semid,&p,1);

        return ret;
}

int V_op() {
        int ret;

        ret=semop(semid,&v,1);

        return ret;
}

int main() {
        key_t key;
        int shmid;
        struct loop_queue *fifo;
        char c;
        int i,n,qn,ret;

        p.sem_num=0;
        p.sem_op=-1;
        p.sem_flg=0;

        v.sem_num=0;
        v.sem_op=1;
        v.sem_flg=0;

        key=ftok("/tmp/count",'e');
        if(key==-1) {
                fprintf(stderr,"ftok() error.\n");
                exit(-1);
        }

        semid=semget(key,1,IPC_CREAT|0600);
        if(semid==-1) {
                perror("semget()");
                exit(-1);
        }

        ret=semctl(semid,0,SETVAL,1);
        if(ret==-1) {
                perror("semctl()");
                exit(-1);
        }

        shmid=shmget(key,sizeof(struct loop_queue),IPC_CREAT|0600);
        if(shmid==-1) {
                perror("shmget()");
                exit(-1);
        }

        fifo=(struct loop_queue *)shmat(shmid,NULL,SHM_RND);
        if((int)fifo==-1) {
                perror("shmat()");
                exit(-1);
        }

        P_op();
        init_queue(fifo);
        V_op();

        while(1) {
                c=rand()%26+'a';
                n=rand()%LEN+1;

                qn=0;

                P_op();
                for(i=0;i<n;i++) {
                        ret=enqueue(fifo,c);
                        if(ret==0) qn++;
                }
                V_op();

                printf("%d x %c enqueue.\n",qn,c);

                sleep(rand()%3+1);
        }

        exit(0);
}

vi out_queue.c(出队)

#include <stdio.h>
#include <stdlib.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>

#define LEN 10

int semid;
struct sembuf p,v;

struct loop_queue {
        int head;
        int tail;
        char mem[LEN];
};

int next(int n) {
        n=(n+1)%LEN;

        return n;
}

int init_queue(struct loop_queue *fifo) {
        fifo->head=0;
        fifo->tail=0;
}

int enqueue(struct loop_queue *fifo,char c) {
        if(fifo->head==next(fifo->tail)) {
                fprintf(stderr,"Queue Full.\n");
                return -1;
        }

        (fifo->mem)[fifo->tail]=c;
        fifo->tail=next(fifo->tail);

        return 0;
}

int dequeue(struct loop_queue *fifo,char *c) {
        if(fifo->head==fifo->tail) {
        //      printf("Queue Null.\n");
                return -1;
        }

        *c=(fifo->mem)[fifo->head];
        fifo->head=next(fifo->head);

        return 0;
}

int main() {
        key_t key;
        int shmid;
        struct loop_queue *fifo;
        char c;
        int i,n,qn,ret;

        p.sem_num=0;
        p.sem_op=-1;
        p.sem_flg=0;

        v.sem_num=0;
        v.sem_op=1;
        v.sem_flg=0;

        key=ftok("/tmp/count",'e');
        if(key==-1) {
                fprintf(stderr,"ftok() error.\n");
                exit(-1);
        }

        semid=semget(key,1,IPC_CREAT|0600);
        if(semid==-1) {
                perror("semget()");
                exit(-1);
        }

        ret=semctl(semid,0,SETVAL,1);
        if(ret==-1) {
                perror("semctl()");
                exit(-1);
        }

        shmid=shmget(key,sizeof(struct loop_queue),IPC_CREAT|0600);
        if(shmid==-1) {
                perror("shmget()");
                exit(-1);
        }

        fifo=(struct loop_queue *)shmat(shmid,NULL,SHM_RND);
        if((int)fifo==-1) {
                perror("shmat()");
                exit(-1);
        }

        while(1) {
                ret=dequeue(fifo,&c);
                if(ret==-1) {
                        continue;
                }
                printf("%c\n",c);
                fflush(stdout);
                usleep(100);
        }

        exit(0);
}