semaphore.cpp

#include <pthread.h>
#include <semaphore.h>
#include <stdio.h>

void* read(void* arg);
void* accu(void* arg);
//sem_one for accu sum
static sem_t sem_one;
//sem_two for read num
static sem_t sem_two;
static int num;

int main(int a, char* n[])
{
    pthread_t tid1, tid2;
    sem_init(&sem_one, 0, 0);
    sem_init(&sem_two, 0, 1);

    pthread_create(&tid1, NULL, read, NULL);
    pthread_create(&tid2, NULL, accu, NULL);

    pthread_join(tid1, NULL);
    pthread_join(tid2, NULL);

    sem_destroy(&sem_one);
    sem_destroy(&sem_two);
    return 0;
}

void* read(void* arg)
{
    int i;
    for (i = 0; i < 5; i++) {
        fputs("input:", stdout);
        sem_wait(&sem_two);
        scanf("%d", &num);
        sem_post(&sem_one);
    }
    return NULL;
}

void* accu(void* arg)
{
    int sum = 0, i;
    for (i = 0; i < 5; i++) {
        sem_wait(&sem_one);
        sum += num;
        sem_post(&sem_two);
    }
    printf("result:%d \n", sum);
    return NULL;
}