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

#define STACKSIZE 20

struct stack 
{
    int count;
    int val[STACKSIZE];
};

pthread_mutex_t mut;
pthread_mutex_t output;

void print(int v)
{
    pthread_mutex_lock(&output);
    printf("Thread %u says: %d\n",pthread_self(),v);
    fflush(stdout);
    pthread_mutex_unlock(&output);
}

void prints(char* s)
{
    pthread_mutex_lock(&output);
    printf("Thread %u says: %s\n",pthread_self(),s);
    fflush(stdout);
    pthread_mutex_unlock(&output);
}

int full(struct stack* ss)
{
    return (ss->count==STACKSIZE);
}

int empty(struct stack* ss)
{
    return (ss->count==0);
}

/* Doesn't check full(). It really should */
void add(struct stack* ss, int v)
{
    pthread_mutex_lock(&mut);
    ss->val[ss->count]=v;
    prints("Adds");
    (ss->count)++;
    pthread_mutex_unlock(&mut);
}

/* Doesn't check empty(). It really should */
int del(struct stack* ss)
{
    int res;
    pthread_mutex_lock(&mut);
    (ss->count)--;
    res=ss->val[ss->count];
/*    printf("Read %d got %d\n",ss->count, res); */
    pthread_mutex_unlock(&mut);
    return res;
}



void* adder(void* in) 
{
    int v=0;
    int j=0;
    struct stack* ss=(struct stack*)in;
    while (1) {
        if (!full(ss)) {
            add(ss,v++);
        }
        pthread_yield();
    }
    return 0;
}

void* reader(void* in)
{
    struct stack* ss=(struct stack*)in;
    int j;
    prints("Looping");
    while(1) {
        if (!empty(ss)) {
            j=del(ss);
            print(j);
        }
        pthread_yield();
    }

}

int main(int argc, char** argv)
{
    pthread_t tid,r1,r2;
    struct stack ss;
    ss.count=0;
    pthread_mutex_init(&mut,0);
    pthread_mutex_init(&output,0);
    pthread_create(&tid, 0, adder, &ss);
    pthread_create(&r1,0,reader,&ss);
    pthread_create(&r2,0,reader,&ss);
    printf("adder=%d reader=%d reader=%d\n",tid,r1,r2);
    pthread_exit(0);	/* we want the threads to keep going */
    return 0;
}