gistfile1.cpp

#include <iostream>
#include <cstdlib>
#include <pthread.h>

using namespace std;

#define LOOP_COUNT 30
#define NUM_THREADS 4
#define Q_SIZE 5

struct Fifo {
    pthread_mutex_t mutex;
    int data[Q_SIZE];

    int head;
    int count;

    Fifo() : head(0), count(0) {
        pthread_mutex_init(&mutex, 0);
    }

    void put(int value) {
        while (1) {
            pthread_mutex_lock(&mutex);

            if (count < Q_SIZE) {
                data[(count + head) % Q_SIZE] = value;
                ++count;
                pthread_mutex_unlock(&mutex);
                return;
            }

            pthread_mutex_unlock(&mutex);
        }
    }

    int take(void) {
        while (1) {
            pthread_mutex_lock(&mutex);

            if (count > 0) {
                int ret = data[head % Q_SIZE];
                ++head;
                --count;
                pthread_mutex_unlock(&mutex);
                return ret;
            }

            pthread_mutex_unlock(&mutex);
        }
    }
};

struct ThreadInfo {
    Fifo *fifo;
    int thread_num;
};

static void qlog(int thread_num, int val, bool is_put) {
    static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
    pthread_mutex_lock(&mutex);
    std::cerr << " thread " << thread_num <<
                 (is_put ? " putting " : " took ") << val << std::endl;
    pthread_mutex_unlock(&mutex);
}

static void *test_q(void *data) {
    ThreadInfo *info = reinterpret_cast<ThreadInfo*>(data);
    Fifo* fifo = info->fifo;
    bool prod_cons = info->thread_num % 2;
    int loop_count = 0;
    while (++loop_count <= LOOP_COUNT) {
        if (prod_cons) {
            int val = rand();
            qlog(info->thread_num, val, 1);
            fifo->put(val);
        }
        else {
            int val = fifo->take();
            qlog(info->thread_num, val, 0);
        }
    }
    return 0;
}

int main()
{
    srand(time(0));
    pthread_t threads[NUM_THREADS];
    struct ThreadInfo infos[NUM_THREADS];
    Fifo fifo;
    for (int i = 0; i < NUM_THREADS; i++) {
        infos[i].fifo = &fifo;
        infos[i].thread_num = i;
        pthread_create(threads + i, 0, test_q, infos + i);
    }
    for (int i = 0; i < NUM_THREADS; i++) {
        pthread_join(threads[i], 0);
    }

    return 0;
}