src/audio/arts/SDL_artsaudio.c

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2006 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library 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
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Sam Lantinga
    slouken@libsdl.org
*/
#include "SDL_config.h"

/* Allow access to a raw mixing buffer */

#include "SDL_timer.h"
#include "SDL_audio.h"
#include "../SDL_audiomem.h"
#include "../SDL_audio_c.h"
#include "SDL_artsaudio.h"

#ifdef SDL_AUDIO_DRIVER_ARTS_DYNAMIC
#include "SDL_name.h"
#include "SDL_loadso.h"
#else
#define SDL_NAME(X)	X
#endif

/* The tag name used by artsc audio */
#define ARTS_DRIVER_NAME         "arts"

/* Audio driver functions */
static int ARTS_OpenAudio(_THIS, SDL_AudioSpec * spec);
static void ARTS_WaitAudio(_THIS);
static void ARTS_PlayAudio(_THIS);
static Uint8 *ARTS_GetAudioBuf(_THIS);
static void ARTS_CloseAudio(_THIS);

#ifdef SDL_AUDIO_DRIVER_ARTS_DYNAMIC

static const char *arts_library = SDL_AUDIO_DRIVER_ARTS_DYNAMIC;
static void *arts_handle = NULL;
static int arts_loaded = 0;

static int (*SDL_NAME(arts_init)) (void);
static void (*SDL_NAME(arts_free)) (void);
static arts_stream_t(*SDL_NAME(arts_play_stream)) (int rate, int bits,
                                                   int channels,
                                                   const char *name);
static int (*SDL_NAME(arts_stream_set)) (arts_stream_t s,
                                         arts_parameter_t param, int value);
static int (*SDL_NAME(arts_stream_get)) (arts_stream_t s,
                                         arts_parameter_t param);
static int (*SDL_NAME(arts_write)) (arts_stream_t s, const void *buffer,
                                    int count);
static void (*SDL_NAME(arts_close_stream)) (arts_stream_t s);

static struct
{
    const char *name;
    void **func;
} arts_functions[] = {
    {
    "arts_init", (void **) &SDL_NAME(arts_init)}, {
    "arts_free", (void **) &SDL_NAME(arts_free)}, {
    "arts_play_stream", (void **) &SDL_NAME(arts_play_stream)}, {
    "arts_stream_set", (void **) &SDL_NAME(arts_stream_set)}, {
    "arts_stream_get", (void **) &SDL_NAME(arts_stream_get)}, {
    "arts_write", (void **) &SDL_NAME(arts_write)}, {
"arts_close_stream", (void **) &SDL_NAME(arts_close_stream)},};

static void
UnloadARTSLibrary()
{
    if (arts_loaded) {
        SDL_UnloadObject(arts_handle);
        arts_handle = NULL;
        arts_loaded = 0;
    }
}

static int
LoadARTSLibrary(void)
{
    int i, retval = -1;

    arts_handle = SDL_LoadObject(arts_library);
    if (arts_handle) {
        arts_loaded = 1;
        retval = 0;
        for (i = 0; i < SDL_arraysize(arts_functions); ++i) {
            *arts_functions[i].func =
                SDL_LoadFunction(arts_handle, arts_functions[i].name);
            if (!*arts_functions[i].func) {
                retval = -1;
                UnloadARTSLibrary();
                break;
            }
        }
    }
    return retval;
}

#else

static void
UnloadARTSLibrary()
{
    return;
}

static int
LoadARTSLibrary(void)
{
    return 0;
}

#endif /* SDL_AUDIO_DRIVER_ARTS_DYNAMIC */

/* Audio driver bootstrap functions */

static int
Audio_Available(void)
{
    int available = 0;

    if (LoadARTSLibrary() < 0) {
        return available;
    }
    if (SDL_NAME(arts_init) () == 0) {
#define ARTS_CRASH_HACK         /* Play a stream so aRts doesn't crash */
#ifdef ARTS_CRASH_HACK
        arts_stream_t stream2;
        stream2 = SDL_NAME(arts_play_stream) (44100, 16, 2, "SDL");
        SDL_NAME(arts_write) (stream2, "", 0);
        SDL_NAME(arts_close_stream) (stream2);
#endif
        available = 1;
        SDL_NAME(arts_free) ();
    }
    UnloadARTSLibrary();

    return available;
}

static void
Audio_DeleteDevice(SDL_AudioDevice * device)
{
    SDL_free(device->hidden);
    SDL_free(device);
    UnloadARTSLibrary();
}

static SDL_AudioDevice *
Audio_CreateDevice(int devindex)
{
    SDL_AudioDevice *this;

    /* Initialize all variables that we clean on shutdown */
    LoadARTSLibrary();
    this = (SDL_AudioDevice *) SDL_malloc(sizeof(SDL_AudioDevice));
    if (this) {
        SDL_memset(this, 0, (sizeof *this));
        this->hidden = (struct SDL_PrivateAudioData *)
            SDL_malloc((sizeof *this->hidden));
    }
    if ((this == NULL) || (this->hidden == NULL)) {
        SDL_OutOfMemory();
        if (this) {
            SDL_free(this);
        }
        return (0);
    }
    SDL_memset(this->hidden, 0, (sizeof *this->hidden));
    stream = 0;

    /* Set the function pointers */
    this->OpenAudio = ARTS_OpenAudio;
    this->WaitAudio = ARTS_WaitAudio;
    this->PlayAudio = ARTS_PlayAudio;
    this->GetAudioBuf = ARTS_GetAudioBuf;
    this->CloseAudio = ARTS_CloseAudio;

    this->free = Audio_DeleteDevice;

    return this;
}

AudioBootStrap ARTS_bootstrap = {
    ARTS_DRIVER_NAME, "Analog Realtime Synthesizer",
    Audio_Available, Audio_CreateDevice, 0
};

/* This function waits until it is possible to write a full sound buffer */
static void
ARTS_WaitAudio(_THIS)
{
    Sint32 ticks;

    /* Check to see if the thread-parent process is still alive */
    {
        static int cnt = 0;
        /* Note that this only works with thread implementations 
           that use a different process id for each thread.
         */
        if (parent && (((++cnt) % 10) == 0)) {  /* Check every 10 loops */
            if (kill(parent, 0) < 0) {
                this->enabled = 0;
            }
        }
    }

    /* Use timer for general audio synchronization */
    ticks = ((Sint32) (next_frame - SDL_GetTicks())) - FUDGE_TICKS;
    if (ticks > 0) {
        SDL_Delay(ticks);
    }
}

static void
ARTS_PlayAudio(_THIS)
{
    int written;

    /* Write the audio data */
    written = SDL_NAME(arts_write) (stream, mixbuf, mixlen);

    /* If timer synchronization is enabled, set the next write frame */
    if (frame_ticks) {
        next_frame += frame_ticks;
    }

    /* If we couldn't write, assume fatal error for now */
    if (written < 0) {
        this->enabled = 0;
    }
#ifdef DEBUG_AUDIO
    fprintf(stderr, "Wrote %d bytes of audio data\n", written);
#endif
}

static Uint8 *
ARTS_GetAudioBuf(_THIS)
{
    return (mixbuf);
}

static void
ARTS_CloseAudio(_THIS)
{
    if (mixbuf != NULL) {
        SDL_FreeAudioMem(mixbuf);
        mixbuf = NULL;
    }
    if (stream) {
        SDL_NAME(arts_close_stream) (stream);
        stream = 0;
    }
    SDL_NAME(arts_free) ();
}

static int
ARTS_OpenAudio(_THIS, SDL_AudioSpec * spec)
{
    int bits, frag_spec;
    SDL_AudioFormat test_format, format;

    /* Reset the timer synchronization flag */
    frame_ticks = 0.0;

    mixbuf = NULL;

    /* Try for a closest match on audio format */
    format = 0;
    bits = 0;
    for (test_format = SDL_FirstAudioFormat(spec->format);
         !format && test_format;) {
#ifdef DEBUG_AUDIO
        fprintf(stderr, "Trying format 0x%4.4x\n", test_format);
#endif
        switch (test_format) {
        case AUDIO_U8:
            bits = 8;
            format = 1;
            break;
        case AUDIO_S16LSB:
            bits = 16;
            format = 1;
            break;
        default:
            format = 0;
            break;
        }
        if (!format) {
            test_format = SDL_NextAudioFormat();
        }
    }
    if (format == 0) {
        SDL_SetError("Couldn't find any hardware audio formats");
        return (-1);
    }
    spec->format = test_format;

    if (SDL_NAME(arts_init) () != 0) {
        SDL_SetError("Unable to initialize ARTS");
        return (-1);
    }
    stream =
        SDL_NAME(arts_play_stream) (spec->freq, bits, spec->channels, "SDL");

    /* Calculate the final parameters for this audio specification */
    SDL_CalculateAudioSpec(spec);

    /* Determine the power of two of the fragment size */
    for (frag_spec = 0; (0x01 << frag_spec) < spec->size; ++frag_spec);
    if ((0x01 << frag_spec) != spec->size) {
        SDL_SetError("Fragment size must be a power of two");
        return (-1);
    }
    frag_spec |= 0x00020000;    /* two fragments, for low latency */

#ifdef ARTS_P_PACKET_SETTINGS
    SDL_NAME(arts_stream_set) (stream, ARTS_P_PACKET_SETTINGS, frag_spec);
#else
    SDL_NAME(arts_stream_set) (stream, ARTS_P_PACKET_SIZE,
                               frag_spec & 0xffff);
    SDL_NAME(arts_stream_set) (stream, ARTS_P_PACKET_COUNT, frag_spec >> 16);
#endif
    spec->size = SDL_NAME(arts_stream_get) (stream, ARTS_P_PACKET_SIZE);

    /* Allocate mixing buffer */
    mixlen = spec->size;
    mixbuf = (Uint8 *) SDL_AllocAudioMem(mixlen);
    if (mixbuf == NULL) {
        return (-1);
    }
    SDL_memset(mixbuf, spec->silence, spec->size);

    /* Get the parent process id (we're the parent of the audio thread) */
    parent = getpid();

    /* We're ready to rock and roll. :-) */
    return (0);
}

/* vi: set ts=4 sw=4 expandtab: */