New audio subsystem.

[jog] / ausys-sdl.c

/* -*-c-*-
 *
 * $Id: ausys-sdl.c,v 1.1 2002/02/02 19:16:28 mdw Exp $
 *
 * Unix-specific (SDL) audio handling
 *
 * (c) 2002 Mark Wooding
 */

/*----- Licensing notice --------------------------------------------------* 
 *
 * This file is part of Jog: Programming for a jogging machine.
 *
 * Jog is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * Jog is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with Jog; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/*----- Revision history --------------------------------------------------* 
 *
 * $Log: ausys-sdl.c,v $
 * Revision 1.1  2002/02/02 19:16:28  mdw
 * New audio subsystem.
 *
 */

/*----- Header files ------------------------------------------------------*/

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

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

#include <sys/types.h>
#include <sys/time.h>
#include <unistd.h>
#include <pthread.h>

#include <SDL.h>

#include <mLib/alloc.h>
#include <mLib/bits.h>
#include <mLib/sub.h>
#include <mLib/trace.h>

#include "au.h"
#include "ausys.h"
#include "err.h"
#include "jog.h"

/*----- Data structures ---------------------------------------------------*/

/* --- Queue of samples to play --- */

typedef struct qnode {
  struct qnode *next;			/* Next item in the queue */
  au_data *a;				/* Pointer to sample data */
} qnode;

/*----- Global variables --------------------------------------------------*/

const char *const ausys_suffix = "wav";

/*----- Static data -------------------------------------------------------*/

static SDL_AudioSpec auspec;		/* Driver's selected parameters */
static qnode *qhead = 0, *qtail = 0;	/* Queue of samples to play */
static qnode *qfree = 0;		/* Queue of samples to free */

static pthread_t tid_free;		/* The sample-freeing thread */
static pthread_mutex_t mx_free;		/* Mutex for @qfree@ */
static pthread_cond_t cv_free;		/* More sample data to free */

static pthread_mutex_t mx_sub;		/* Protects mLib @sub@ functions */

/*----- Thread structure --------------------------------------------------*
 *
 * SDL makes a buffer-stuffing thread that @fill@ is run from.  This function
 * reads samples to play from the queue at @qhead@.  Hence @qhead@ must be
 * locked when it's modified, using @SDL_LockAudio@.
 *
 * In order to keep latency down when new sample data is wanted, we don't do
 * potentially tedious things like freeing sample data blocks in the @fill@
 * thread.  Instead, there's a queue of sample blocks which need freeing, and
 * a separate thread @dofree@ which processes the queue.  The queue, @qfree@
 * is locked by @mx_free@.  When new nodes are added to @qfree@, the
 * condition @cv_free@ is signalled.
 *
 * Finally, the mLib `sub' module isn't thread-safe, so it's locked
 * separately by @mx_sub@.
 *
 * There's an ordering on mutexes.  If you want more than one mutex at a
 * time, you must lock the greatest first.  The ordering is:
 *
 *   SDL_Audio > free > sub
 */

/*----- Main code ---------------------------------------------------------*/

/* --- @fill@ --- *
 *
 * Arguments:	@void *u@ = user data (ignored)
 *		@octet *q@ = pointer to buffer to fill in
 *		@int qsz@ = size of the buffer
 *
 * Returns:	---
 *
 * Use:		Fills an audio buffer with precomputed stuff.
 */

static void fill(void *u, octet *q, int qsz)
{
  static const octet *p = 0;		/* Current place in current sample */
  static size_t sz = 0;			/* How far to go in current sample */
  qnode *qf = 0, **qft = &qf;		/* Samples we've finished with */

  /* --- If @p@ is null we need to get a new sample --- */

  if (!p && qhead) {
    T( trace(T_AUSYS, "ausys: begin playing `%s'", SYM_NAME(qhead->a->s)); )
    p = qhead->a->p;
    sz = qhead->a->sz;
  }

  /* --- Main queue-filling loop --- */

  while (qsz) {
    size_t n;

    /* --- If the queue is empty, play silence --- */

    if (!p) {
      memset(q, auspec.silence, qsz);
      break;
    }

    /* --- Fill the buffer with my sample --- */
exit(0);
    n = qsz;
    if (n > sz)
      n = sz;
    memcpy(q, p, n);
    p += n; q += n;
    sz -= n; qsz -= n;

    /* --- If the sample is used up, throw it away --- */

    if (!sz) {
      qnode *qq = qhead;
      qhead = qq->next;
      if (!qhead)
	qtail = 0;
      T( trace(T_AUSYS, "ausys: put `%s' on free list",
	       SYM_NAME(qq->a->s)); )
      *qft = qq;
      qft = &qq->next;
      if (qhead) {
	T( trace(T_AUSYS, "ausys: begin playing `%s'",
		 SYM_NAME(qhead->a->s)); )
	p = qhead->a->p;
	sz = qhead->a->sz;
      } else {
	T( trace(T_AUSYS, "ausys: sample queue is empty"); )
	p = 0;
	sz = 0;
      }
    }
  }

  /* --- Finally dump freed samples, all in one go --- */

  if (qf) {
    pthread_mutex_lock(&mx_free);
    *qft = qfree;
    qfree = qf;
    pthread_mutex_unlock(&mx_free);
    pthread_cond_signal(&cv_free);
  }
}

/* --- @dofree@ --- *
 *
 * Arguments:	@void *u@ = unused pointer
 *
 * Returns:	An unused pointer.
 *
 * Use:		Frees unwanted sample queue nodes.
 */

static void *dofree(void *u)
{
  qnode *q, *qq;

  pthread_mutex_lock(&mx_free);
  for (;;) {
    T( trace(T_AUSYS, "ausys: dofree sleeping"); )
    pthread_cond_wait(&cv_free, &mx_free);
    T( trace(T_AUSYS, "ausys: dofree woken: work to do"); )

    while (qfree) {
      q = qfree;
      qfree = 0;
      pthread_mutex_lock(&mx_sub);
      while (q) {
	qq = q->next;
	T( trace(T_AUSYS, "ausys: freeing `%s'", SYM_NAME(q->a->s)); )
	au_free_unlocked(q->a);
	DESTROY(q);
	q = qq;
      }
      pthread_mutex_unlock(&mx_sub);
    }
  }
}

/* --- @ausys_init@ --- *
 *
 * Arguments:	---
 *
 * Returns:	---
 *
 * Use:		Does any initialization required by the system-specific audio
 *		handler.
 */

void ausys_init(void)
{
  SDL_AudioSpec want;
  pthread_attr_t ta;
  int e;

  /* --- Crank up the sample-freeing thread --- */

  if ((e = pthread_mutex_init(&mx_free, 0)) != 0 ||
      (e = pthread_mutex_init(&mx_sub, 0)) != 0 ||
      (e = pthread_cond_init(&cv_free, 0)) != 0 ||
      (e = pthread_attr_init(&ta)) != 0 ||
      (e = pthread_attr_setdetachstate(&ta, PTHREAD_CREATE_DETACHED)) != 0 ||
      (e = pthread_create(&tid_free, &ta, dofree, 0)) != 0) {
    err_report(ERR_AUDIO, ERRAU_INIT, e,
	       "couldn't create audio threads: %s", strerror(errno));
    exit(EXIT_FAILURE);
  }
  pthread_attr_destroy(&ta);

  /* --- Crank up the SDL audio subsystem --- */

  if (SDL_Init(SDL_INIT_AUDIO | SDL_INIT_NOPARACHUTE)) {
    err_report(ERR_AUDIO, ERRAU_INIT, 0,
	       "couldn't initialize SDL audio: %s", SDL_GetError());
    exit(EXIT_FAILURE);
  }

  /* --- Open the audio device --- */

  want.freq = 8000;
  want.format = AUDIO_U8;
  want.channels = 1;
  want.samples = 4096;
  want.callback = fill;
  want.userdata = 0;

  if (SDL_OpenAudio(&want, &auspec)) {
    err_report(ERR_AUDIO, ERRAU_INIT, 0,
	       "couldn't open audio device: %s", SDL_GetError());
    exit(EXIT_FAILURE);
  }

  /* --- Prepare whatever needs to be done --- */

  SDL_PauseAudio(0);
  
  T( trace(T_AUSYS, "ausys: initalized ok"); )
}

/* --- @ausys_shutdown@ --- *
 *
 * Arguments:	---
 *
 * Returns:	---
 *
 * Use:		Does any tidying up required.
 */

void ausys_shutdown(void)
{
  /* --- Busy-wait until sound buffer empties --- */

  while (qhead) {
    struct timeval tv = { 0, 100000 };
    select(0, 0, 0, 0, &tv);
  }

  /* --- Shut stuff down --- */

  pthread_cancel(tid_free);
  SDL_CloseAudio();
  SDL_Quit();

  T( trace(T_AUSYS, "ausys: shut down ok"); )
}

/* --- @ausys_lock@, @ausys_unlock@ --- *
 *
 * Arguments:	---
 *
 * Returns:	---
 *
 * Use:		Locks or unlocks the audio subsystem.  This protects the
 *		audio queue from becoming corrupted during all the tedious
 *		asynchronous stuff.
 */

void ausys_lock(void)
{
  pthread_mutex_lock(&mx_free);
  pthread_mutex_lock(&mx_sub);
  T( trace(T_AUSYS, "ausys: acquired lock"); )
}

void ausys_unlock(void)
{
  pthread_mutex_unlock(&mx_sub);
  pthread_mutex_unlock(&mx_free);
  T( trace(T_AUSYS, "ausys: released lock"); )
}

/* --- @ausys_decode@ --- *
 *
 * Arguments:	@au_sample *s@ = pointer to sample block
 *		@const void *p@ = pointer to sample file contents
 *		@size_t sz@ = size of sample file contents
 *
 * Returns:	Pointer to a sample data structure.
 *
 * Use:		Decodes a WAV file into something the system-specific layer
 *		actually wants to deal with.
 */

au_data *ausys_decode(au_sample *s, const void *p, size_t sz)
{
  au_data *a;
  SDL_AudioCVT cvt;
  SDL_AudioSpec spec;
  SDL_RWops *rw;
  Uint8 *buf;
  Uint32 len;
  void *q;

  /* --- Firstly, extract the audio data from the WAV file --- */

  rw = SDL_RWFromMem((void *)p, sz);
  if (!SDL_LoadWAV_RW(rw, 1, &spec, &buf, &len)) {
    err_report(ERR_AUDIO, ERRAU_OPEN, 0,
	       "can't read WAV file for `%s': %s",
	       SYM_NAME(s), SDL_GetError());
    goto fail_0;
  }

  /* --- Now convert that to the driver's expected format --- */

  if (SDL_BuildAudioCVT(&cvt, spec.format, spec.channels, spec.freq,
			auspec.format, auspec.channels, auspec.freq) == -1) {
    err_report(ERR_AUDIO, ERRAU_OPEN, 0,
	       "can't build conversion structure for `%s': %s",
	       SYM_NAME(s), SDL_GetError());
    goto fail_1;
  }

  cvt.buf = xmalloc(len * cvt.len_mult);
  cvt.len = len;
  memcpy(cvt.buf, buf, len);
  SDL_FreeWAV(buf);

  if (SDL_ConvertAudio(&cvt)) {
    err_report(ERR_AUDIO, ERRAU_OPEN, 0,
	       "can't convert `%s': %s", SYM_NAME(s), SDL_GetError());
    goto fail_2;
  }

  /* --- Now fiddle with buffers --- */

  sz = len * cvt.len_ratio;
  if (cvt.len_ratio >= 1)
    q = cvt.buf;
  else {
    q = xmalloc(sz);
    memcpy(q, cvt.buf, sz);
    xfree(cvt.buf);
  }

  /* --- Construct a new node --- */
  
  pthread_mutex_lock(&mx_sub);
  a = CREATE(au_data);
  pthread_mutex_unlock(&mx_sub);
  a->p = q;
  a->sz = sz;
  
  T( trace(T_AUSYS, "ausys: decoded `%s' ok", SYM_NAME(s)); )
  return (a);

  /* --- Tidy up after errors --- */

fail_2:
  xfree(cvt.buf);
  goto fail_0;
fail_1:
  SDL_FreeWAV(buf);
fail_0:
  return (0);    
}

/* --- @ausys_queue@ --- *
 *
 * Arguments:	@au_data *a@ = an audio thingy to play
 *
 * Returns:	---
 *
 * Use:		Queues an audio sample to be played.  The sample should be
 *		freed (with @au_free@) when it's no longer wanted.
 */

void ausys_queue(au_data *a)
{
  qnode *q;

  pthread_mutex_lock(&mx_sub);
  q = CREATE(qnode);
  pthread_mutex_unlock(&mx_sub);
  q->next = 0;
  q->a = a;
  SDL_LockAudio();
  if (qtail)
    qtail->next = q;
  else
    qhead = q;
  qtail = q;
  SDL_UnlockAudio();
  T( trace(T_AUSYS, "ausys: queuing `%s'", SYM_NAME(a->s)); )
}

/* --- @ausys_free@ --- *
 *
 * Arguments:	@au_data *a@ = an audio thingy to free
 *
 * Returns:	---
 *
 * Use:		Frees a decoded audio sample.
 */

void ausys_free(au_data *a)
{
  xfree(a->p);
  DESTROY(a);
  T( trace(T_AUSYS, "ausys: freeing data for `%s' ok", SYM_NAME(a->s)); )
}

/*----- That's all, folks -------------------------------------------------*/