pthread cond 生产者消费者（复习）

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#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <pthread.h>#define BUFFER_SIZE 8struct products{    int buffer[BUFFER_SIZE];    pthread_mutex_t lock;    pthread_cond_t not_empty;    pthread_cond_t not_full;    int pos_read_from;    int pos_write_to;};int buffer_is_full(struct products *products){    if ((products->pos_write_to + 1) % BUFFER_SIZE == products->pos_read_from) {        return 1;    }    else {        return 0;    }}int buffer_is_empty(struct products *products){    if (products->pos_write_to == products->pos_read_from) {        return 1;    }    else {        return 0;    }}void produce(struct products *products, int item){    pthread_mutex_lock(&products->lock);    while (buffer_is_full(products)) {        pthread_cond_wait(&products->not_full, &products->lock);            }     products->buffer[products->pos_write_to] = item;    printf("pos write to:%d\n", products->pos_write_to);    products->pos_write_to++;        if (products->pos_write_to >= BUFFER_SIZE) {        products->pos_write_to = 0;    }     pthread_cond_signal(&products->not_empty);    pthread_mutex_unlock(&products->lock);}int consume(struct products *products){    int item;    pthread_mutex_lock(&products->lock);    while (buffer_is_empty(products)) {        pthread_cond_wait(&products->not_empty, &products->lock);    }    item = products->buffer[products->pos_read_from];    printf("pos write to:%d\n", products->pos_read_from);    products->pos_read_from++;        if (products->pos_read_from >= BUFFER_SIZE) {        products->pos_read_from = 0;    }        pthread_cond_signal(&products->not_full);  //because of context switch    pthread_mutex_unlock(&products->lock);    return item;}#define END_FLAG (-1)struct products products;void * produce_thread(void *data){    int i;    for (i=0; i<16; i++) {        printf("produce %d\n", i);        produce(&products, i);    }    produce(&products, END_FLAG);    return NULL;}void * consume_thread(void *data){    int item;    while (1) {        item = consume(&products);        if (END_FLAG == item) {            break;        }        printf("consumer:%d\n", item);    }    return NULL;}int init_products(){    if (pthread_mutex_init(&products.lock, NULL) != 0) {        perror("mutex init failed");        exit(-1);    }    if (pthread_cond_init(&products.not_full, NULL) != 0) {        perror("cond not full init failed");        exit (-1);    }    if (pthread_cond_init(&products.not_empty, NULL) != 0) {        perror("cond not empty init failed");        exit (-1);    }    products.pos_read_from = 0;    products.pos_write_to = 0;}int main(int argc, char *argv[]){    int res;    pthread_t producer, consumer;    pthread_create(&producer, NULL, &produce_thread, NULL);    pthread_create(&consumer, NULL, &consume_thread, NULL);    pthread_join(producer, (void *)&res);    pthread_join(consumer, (void *)&res);    return 0;}
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