#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>

#include <sys/ioctl.h>
#include <sys/soundcard.h>

#define audio_flush(fd)  audio_buffer((fd), 0, 0)

#define AUDIO_DEVICE	"/dev/audio"
#define AUDIO_FILLSZ	4608
#define MIXER_DEVICE	"/dev/mixer"

#if defined(EMPEG_H_AVAILABLE)
#include <linux/empeg.h>
#else
#define EMPEG_MIXER_MAGIC 'm'
#define EMPEG_MIXER_WRITE_SOURCE _IOW(EMPEG_MIXER_MAGIC, 0, int)
#define EMPEG_MIXER_WRITE_FLAGS _IOW(EMPEG_MIXER_MAGIC, 1, int)
#define EMPEG_MIXER_SET_SAM _IOW(EMPEG_MIXER_MAGIC, 15, int)
#endif

static int output(int fd, void const *buf, unsigned int len)
{
  char const *ptr = (const char *)buf;
  int wrote;

  while (len) {
    wrote = write(fd, ptr, len);
    if (wrote == -1) {
      if (errno == EINTR)
	continue;
      else
	return -1;
    }

    ptr += wrote;
    len -= wrote;
  }

  return 0;
}

static int audio_buffer(int fd, void const *buf, unsigned int len)
{
  char const *ptr = (const char *)buf;
  static char hold[AUDIO_FILLSZ];
  static unsigned int held;
  unsigned int left, grab;

  if (len == 0) {
    if (held) {
      memset(&hold[held], 0, &hold[AUDIO_FILLSZ] - &hold[held]);
      held = 0;

      return output(fd, hold, AUDIO_FILLSZ);
    }

    return 0;
  }

  if (held == 0 && len == AUDIO_FILLSZ)
    return output(fd, ptr, len);

  left = AUDIO_FILLSZ - held;

  while (len) {
    grab = len < left ? len : left;

    memcpy(&hold[held], ptr, grab);
    held += grab;
    left -= grab;

    ptr += grab;
    len -= grab;

    if (left == 0) {
      if (output(fd, hold, AUDIO_FILLSZ) == -1)
	return -1;

      held = 0;
      left = AUDIO_FILLSZ;
    }
  }

  return 0;
}

static int mixer_init(int fd)
{
  int source, soft_audio_mute, mute;

  source = SOUND_MASK_PCM;
  if (ioctl(fd, EMPEG_MIXER_WRITE_SOURCE, &source) == -1) {
    perror("ioctl(EMPEG_MIXER_WRITE_SOURCE)");
    return 3;
  }

  soft_audio_mute = 0;
  if (ioctl(fd, EMPEG_MIXER_SET_SAM, &soft_audio_mute) == -1) {
    perror("ioctl(EMPEG_MIXER_SET_SAM)");
    return -1;
  }

  mute = 0;
  if (ioctl(fd, EMPEG_MIXER_WRITE_FLAGS, &mute) == -1) {
    perror("ioctl(EMPEG_MIXER_WRITE_FLAGS)");
    return -1;
  }


  return 0;
}


int main(int argc, char *argv[])
{
  static char buffer[AUDIO_FILLSZ];
  int audio_fd, mixer_fd;
  unsigned int len;

  if ((audio_fd = open(AUDIO_DEVICE, O_WRONLY)) == -1) {
    perror(AUDIO_DEVICE);
    return 1;
  }

  if ((mixer_fd = open(MIXER_DEVICE, O_WRONLY)) == -1) {
    perror(MIXER_DEVICE);
    return 1;
  }

  if (mixer_init(mixer_fd) == -1) {
    close(audio_fd);
    close(mixer_fd);
    return 2;
  }

  while ((len = fread(buffer, 4, AUDIO_FILLSZ / 4, stdin))) {
    if (audio_buffer(audio_fd, buffer, 4 * len) == -1) {
      perror("write");
      return 3;
    }
  }

  if (ferror(stdin)) {
    perror("read");
    return 4;
  }

  if (audio_flush(audio_fd) == -1) {
    perror("write");
    return 3;
  }

  if (close(audio_fd) == -1) {
    perror("close");
    return 5;
  }

  return 0;
}