#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include <pthread.h>
#include <stdio.h>
#include <semaphore.h>

/* buffer of downloaded data */
char download_buffer[512];
sem_t download_empty;
sem_t download_full;

/* buffer of decompressed data */
char decompress_buffer[512];
sem_t decompress_empty;
sem_t decompress_full;

/* when to quit the program */
volatile int quit = 0;

/* the function called for the first thread, downloading the video frames */
void* download(void* p) {
    /* loop forever */
    while (!quit) {
        /* wait until the buffer is empty */
        sem_wait(&download_empty);

        /* fill it with data (really just a string from stdin) */
        scanf("%s", download_buffer);

        /* if EOF, quit */
        if (feof(stdin)) {
            quit = 1;
        }

        /* tell the decompress that it's full */
        sem_post(&download_full);
    }

    return NULL;
}

/* the function called for the second thread, decompressing the video */
void* decompress(void* p) {
    /* loop forever */
    while (!quit) {
        /* wait for the download buffer to be full */
        sem_wait(&download_full);

        /* wait for the decompress buffer to be empty */
        sem_wait(&decompress_empty);

        /* move from download buffer to decompress */
        strcpy(decompress_buffer, download_buffer);

        /* tell download thread the buffer is empty */
        sem_post(&download_empty);

        /* capitalize it */
        int i;
        for (i = 0; i < strlen(decompress_buffer); i++) {
            decompress_buffer[i] = toupper(decompress_buffer[i]);
        }

        /* tell display thread the buffer is full */
        sem_post(&decompress_full);
    }

    return NULL;
}

/* the function called for the third thread, displaying the video */
void* display(void* p) {
    /* loop forever */
    while (!quit) {
        /* wait for the decompress buffer to be full */
        sem_wait(&decompress_full);

        /* display it */
        printf("%s\n", decompress_buffer);

        /* tell the thread it's empty */
        sem_post(&decompress_empty);
    }

    return NULL;
}


int main() {
    /* the threads */
    pthread_t a, b, c;

    /* setup the semaphores to show all buffers empty */
    sem_init(&download_empty, 0, 1);
    sem_init(&download_full, 0, 0);
    sem_init(&decompress_empty, 0, 1);
    sem_init(&decompress_full, 0, 0);

    /* spawn all threads */
    pthread_create(&a, NULL, download, NULL);
    pthread_create(&b, NULL, decompress, NULL);
    pthread_create(&c, NULL, display, NULL);

    /* join all threads */
    pthread_join(a, NULL);
    pthread_join(b, NULL);
    pthread_join(c, NULL);

    return 0;
}