#include <stdio.h>

#include <stdlib.h>

#include <pthread.h>



#define NBUF 5

#define N 10



// shared global variables

int buf[NBUF];      // circular buffers

int head, tail;     // indices

int data;           // number of full buffers

pthread_mutex_t mutex;      // mutex lock

pthread_cond_t empty, full; // condition variables



int init()

{

    head = tail = data = 0;

    pthread_mutex_init(&mutex, NULL);

    pthread_cond_init(&full, NULL);

    pthread_cond_init(&empty, NULL);

}



void *producer()

{

    int i;

    pthread_t me = pthread_self();

    for (i=0; i<N; i++){    // try to put N items into buf[]

        pthread_mutex_lock(&mutex);     // lock mutex

        if (data == NBUF){

            printf("producer %lu: all bufs FULL: wait\n", me);

            pthread_cond_wait(&empty, &mutex);  // wait

        }

        buf[head++] = i+1;                  // item = 1,2,. .,N

        head %= NBUF;                       // circular bufs

        data++;                             // inc data by 1

        printf("producer %lu: data=%d value=%d\n", me, data, i+1);

        pthread_mutex_unlock(&mutex);       // unlock mutex

        pthread_cond_signal(&full);         // unblock a consumer, if any

    }

    printf("producer %lu : exit\n", me);

}



void *consumer ()

{

    int i, c;

    pthread_t me = pthread_self();

    for (i=0; i<N; i++){

        pthread_mutex_lock(&mutex);       // lock mutex

        if (data == 0){

            printf("consumer %lu: all bufs EMPTY: wait\n", me);

            pthread_cond_wait(&full, &mutex);   // wait

        }

        c = buf[tail++];                // get an item

        tail %= NBUF;

        data--;                         // dec data by 1

        printf("consumer %lu : value=%d\n", me, c);

        pthread_mutex_unlock(&mutex);   // unlock mutex

        pthread_cond_signal(&empty);    // unblock a producer, if any

    }

    printf("consumer %lu: exit\n", me);

}



int main()

{

    pthread_t pro, con;

    init();

    printf("main: create producer and consumer threads\n");

    pthread_create(&pro, NULL, producer, NULL);

    pthread_create(&con, NULL, consumer, NULL);

    printf("main: join with threads\n");

    pthread_join(pro, NULL);

    pthread_join(con, NULL);

    printf("main: exit\n");

}