#include <stdio.h>
#include <stdio.h>
#include <stddef.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <fcntl.h>

#include <sys/soundcard.h>

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

#define BUFFER_SIZE 4
#define SAMPLE_SIZE 16384

#define AUDIODEV "/dev/dsp"
#define STEREO 1
#define SPEED 48000

int audio_fd;

struct prodcons {
  unsigned char *buffer[BUFFER_SIZE];
  unsigned int size[BUFFER_SIZE];
  int readpos, writepos;
  sem_t sem_read;
  sem_t sem_write;
};

void
init(struct prodcons *b)
{
  int i;
  int stereo = STEREO;
  int speed = SPEED;

  audio_fd = open(AUDIODEV, O_RDWR);
  if (audio_fd <= 0) {
    perror("open");
    exit(1);
  }

  if (ioctl(audio_fd, SNDCTL_DSP_STEREO, &stereo)==-1) {
    perror("SNDCTL_DSP_STEREO");
    exit(1);
  }

  if (ioctl(audio_fd, SNDCTL_DSP_SPEED, &speed)==-1) {
    perror("SNDCTL_DSP_SPEED");
    exit(1);
  }

  for (i=0; i<BUFFER_SIZE; i++) {
    b->buffer[i] = (unsigned char *)malloc(SAMPLE_SIZE);
    b->size[i] = 0;
  }
  sem_init(&b->sem_write, 0, BUFFER_SIZE - 1);
  sem_init(&b->sem_read, 0, 0);
  b->readpos = 0;
  b->writepos = 0;
}

void
put(struct prodcons *b, unsigned char *data, unsigned int size)
{
  sem_wait(&b->sem_write);
  memcpy(b->buffer[b->writepos], data, size);
  b->size[b->writepos] = size;
  b->writepos++;
  if (b->writepos >= BUFFER_SIZE)
    b->writepos = 0;
  sem_post(&b->sem_read);
}

int
get(struct prodcons *b, unsigned char *data, unsigned int *size)
{
  sem_wait(&b->sem_read);
  *size = b->size[b->readpos];
  memcpy(data, b->buffer[b->readpos], *size);
  b->readpos++;
  if (b->readpos >= BUFFER_SIZE)
    b->readpos = 0;
  sem_post(&b->sem_write);
  return 0;
}

#define OVER (-1)

struct prodcons buffer;

void *
producer(void *data)
{
  unsigned char audio_rbuf[SAMPLE_SIZE];
  unsigned int rbytes;
  for (;;) {
    rbytes = read(audio_fd, audio_rbuf, SAMPLE_SIZE);
    if (rbytes > 0)
      put(&buffer, audio_rbuf, rbytes);
  }
  return NULL;
}

void *
consumer(void *data)
{
  unsigned char audio_wbuf[SAMPLE_SIZE];
  unsigned int wbytes;
  for (;;) {
    get(&buffer, audio_wbuf, &wbytes);
    if (wbytes > 0)
      write(audio_fd, audio_wbuf, wbytes);
  }
  return NULL;
}

int
main()
{
  pthread_t th_a, th_b;
  void *retval;

  init(&buffer);

  pthread_create(&th_a, NULL, producer, 0);
  pthread_create(&th_b, NULL, consumer, 0);

  pthread_join(th_a, &retval);
  pthread_join(th_b, &retval);

  return 0;
}