src/audio/SDL_audio.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.h"
#include "SDL_audio_c.h"
#include "SDL_audiomem.h"
#include "SDL_sysaudio.h"

#define _THIS	SDL_AudioDevice *this

static SDL_AudioDriver current_audio;
static SDL_AudioDevice *open_devices[16];

/* !!! FIXME: These are wordy and unlocalized... */
#define DEFAULT_OUTPUT_DEVNAME "System audio output device"
#define DEFAULT_INPUT_DEVNAME "System audio capture device"


/*
 * Not all of these will be compiled and linked in, but it's convenient
 *  to have a complete list here and saves yet-another block of #ifdefs...
 *  Please see bootstrap[], below, for the actual #ifdef mess.
 */
extern AudioBootStrap BSD_AUDIO_bootstrap;
extern AudioBootStrap DSP_bootstrap;
extern AudioBootStrap DMA_bootstrap;
extern AudioBootStrap ALSA_bootstrap;
extern AudioBootStrap QNXNTOAUDIO_bootstrap;
extern AudioBootStrap SUNAUDIO_bootstrap;
extern AudioBootStrap DMEDIA_bootstrap;
extern AudioBootStrap ARTS_bootstrap;
extern AudioBootStrap ESD_bootstrap;
extern AudioBootStrap NAS_bootstrap;
extern AudioBootStrap DSOUND_bootstrap;
extern AudioBootStrap WINWAVEOUT_bootstrap;
extern AudioBootStrap PAUDIO_bootstrap;
extern AudioBootStrap BEOSAUDIO_bootstrap;
extern AudioBootStrap COREAUDIO_bootstrap;
extern AudioBootStrap SNDMGR_bootstrap;
extern AudioBootStrap MINTAUDIO_GSXB_bootstrap;
extern AudioBootStrap MINTAUDIO_MCSN_bootstrap;
extern AudioBootStrap MINTAUDIO_STFA_bootstrap;
extern AudioBootStrap MINTAUDIO_XBIOS_bootstrap;
extern AudioBootStrap MINTAUDIO_DMA8_bootstrap;
extern AudioBootStrap DISKAUD_bootstrap;
extern AudioBootStrap DUMMYAUD_bootstrap;
extern AudioBootStrap DCAUD_bootstrap;
extern AudioBootStrap MMEAUDIO_bootstrap;
extern AudioBootStrap DART_bootstrap;


/* Available audio drivers */
static AudioBootStrap *bootstrap[] = {
#if SDL_AUDIO_DRIVER_BSD
    &BSD_AUDIO_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_OSS
    &DSP_bootstrap,
    &DMA_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_ALSA
    &ALSA_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_QNXNTO
    &QNXNTOAUDIO_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_SUNAUDIO
    &SUNAUDIO_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_DMEDIA
    &DMEDIA_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_ARTS
    &ARTS_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_ESD
    &ESD_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_NAS
    &NAS_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_DSOUND
    &DSOUND_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_WINWAVEOUT
    &WINWAVEOUT_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_PAUDIO
    &PAUDIO_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_BEOSAUDIO
    &BEOSAUDIO_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_COREAUDIO
    &COREAUDIO_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_SNDMGR
    &SNDMGR_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_MINT
    &MINTAUDIO_GSXB_bootstrap,
    &MINTAUDIO_MCSN_bootstrap,
    &MINTAUDIO_STFA_bootstrap,
    &MINTAUDIO_XBIOS_bootstrap,
    &MINTAUDIO_DMA8_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_DISK
    &DISKAUD_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_DUMMY
    &DUMMYAUD_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_DC
    &DCAUD_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_MMEAUDIO
    &MMEAUDIO_bootstrap,
#endif
#if SDL_AUDIO_DRIVER_DART
    &DART_bootstrap,
#endif
    NULL
};

/*
 * If non-zero, use legacy behaviour (memset the callback buffer before call).
 * Changed to NOT initializing the buffer before the callback in 1.2.12.
 * Set environment SDL_AUDIO_MUST_INIT_BUFFERS=1 to get old behaviour.
 */
static int must_init_callback_buffer = 0;

static SDL_AudioDevice *
get_audio_device(SDL_AudioDeviceID id)
{
    id--;
    if ((id >= SDL_arraysize(open_devices)) || (open_devices[id] == NULL)) {
        SDL_SetError("Invalid audio device ID");
        return NULL;
    }

    return open_devices[id];
}


/* stubs for audio drivers that don't need a specific entry point... */
static int
SDL_AudioDetectDevices_Default(int iscapture)
{
    return -1;
}
static void
SDL_AudioThreadInit_Default(_THIS)
{                               /* no-op. */
}
static void
SDL_AudioWaitDevice_Default(_THIS)
{                               /* no-op. */
}
static void
SDL_AudioPlayDevice_Default(_THIS)
{                               /* no-op. */
}
static Uint8 *
SDL_AudioGetDeviceBuf_Default(_THIS)
{
    return NULL;
}
static void
SDL_AudioWaitDone_Default(_THIS)
{                               /* no-op. */
}
static void
SDL_AudioCloseDevice_Default(_THIS)
{                               /* no-op. */
}
static void
SDL_AudioDeinitialize_Default(void)
{                               /* no-op. */
}

static int
SDL_AudioOpenDevice_Default(_THIS, const char *devname, int iscapture)
{
    return 0;
}

static const char *
SDL_AudioGetDeviceName_Default(int index, int iscapture)
{
    SDL_SetError("No such device");
    return NULL;
}

static void
SDL_AudioLockDevice_Default(SDL_AudioDevice * device)
{
    if (device->thread && (SDL_ThreadID() == device->threadid)) {
        return;
    }
    SDL_mutexP(device->mixer_lock);
}

static void
SDL_AudioUnlockDevice_Default(SDL_AudioDevice * device)
{
    if (device->thread && (SDL_ThreadID() == device->threadid)) {
        return;
    }
    SDL_mutexV(device->mixer_lock);
}


static void
finalize_audio_entry_points(void)
{
    /*
     * Fill in stub functions for unused driver entry points. This lets us
     *  blindly call them without having to check for validity first.
     */

#define FILL_STUB(x) \
        if (current_audio.impl.x == NULL) { \
            current_audio.impl.x = SDL_Audio##x##_Default; \
        }
    FILL_STUB(DetectDevices);
    FILL_STUB(GetDeviceName);
    FILL_STUB(OpenDevice);
    FILL_STUB(ThreadInit);
    FILL_STUB(WaitDevice);
    FILL_STUB(PlayDevice);
    FILL_STUB(GetDeviceBuf);
    FILL_STUB(WaitDone);
    FILL_STUB(CloseDevice);
    FILL_STUB(LockDevice);
    FILL_STUB(UnlockDevice);
    FILL_STUB(Deinitialize);
#undef FILL_STUB
}


/* The general mixing thread function */
int SDLCALL
SDL_RunAudio(void *devicep)
{
    SDL_AudioDevice *device = (SDL_AudioDevice *) devicep;
    Uint8 *stream;
    int stream_len;
    void *udata;
    void (SDLCALL * fill) (void *userdata, Uint8 * stream, int len);
    int silence;

    /* Perform any thread setup */
    device->threadid = SDL_ThreadID();
    current_audio.impl.ThreadInit(device);

    /* Set up the mixing function */
    fill = device->spec.callback;
    udata = device->spec.userdata;

    if (device->convert.needed) {
        if (device->convert.src_format == AUDIO_U8) {
            silence = 0x80;
        } else {
            silence = 0;
        }
        stream_len = device->convert.len;
    } else {
        silence = device->spec.silence;
        stream_len = device->spec.size;
    }

    /* Loop, filling the audio buffers */
    while (device->enabled) {

        /* Fill the current buffer with sound */
        if (device->convert.needed) {
            if (device->convert.buf) {
                stream = device->convert.buf;
            } else {
                continue;
            }
        } else {
            stream = current_audio.impl.GetDeviceBuf(device);
            if (stream == NULL) {
                stream = device->fake_stream;
            }
        }

        /* New code should fill buffer or set it to silence themselves. */
        if ( must_init_callback_buffer ) {
            SDL_memset(stream, silence, stream_len);
        }

        if (!device->paused) {
            SDL_mutexP(device->mixer_lock);
            (*fill) (udata, stream, stream_len);
            SDL_mutexV(device->mixer_lock);
        }

        /* Convert the audio if necessary */
        if (device->convert.needed) {
            SDL_ConvertAudio(&device->convert);
            stream = current_audio.impl.GetDeviceBuf(device);
            if (stream == NULL) {
                stream = device->fake_stream;
            }
            SDL_memcpy(stream, device->convert.buf, device->convert.len_cvt);
        }

        /* Ready current buffer for play and change current buffer */
        if (stream != device->fake_stream) {
            current_audio.impl.PlayDevice(device);
        }

        /* Wait for an audio buffer to become available */
        if (stream == device->fake_stream) {
            SDL_Delay((device->spec.samples * 1000) / device->spec.freq);
        } else {
            current_audio.impl.WaitDevice(device);
        }
    }

    /* Wait for the audio to drain.. */
    current_audio.impl.WaitDone(device);

    return (0);
}


static SDL_AudioFormat
SDL_ParseAudioFormat(const char *string)
{
#define CHECK_FMT_STRING(x) if (SDL_strcmp(string, #x) == 0) return AUDIO_##x
    CHECK_FMT_STRING(U8);
    CHECK_FMT_STRING(S8);
    CHECK_FMT_STRING(U16LSB);
    CHECK_FMT_STRING(S16LSB);
    CHECK_FMT_STRING(U16MSB);
    CHECK_FMT_STRING(S16MSB);
    CHECK_FMT_STRING(U16SYS);
    CHECK_FMT_STRING(S16SYS);
    CHECK_FMT_STRING(U16);
    CHECK_FMT_STRING(S16);
    CHECK_FMT_STRING(S32LSB);
    CHECK_FMT_STRING(S32MSB);
    CHECK_FMT_STRING(S32SYS);
    CHECK_FMT_STRING(S32);
    CHECK_FMT_STRING(F32LSB);
    CHECK_FMT_STRING(F32MSB);
    CHECK_FMT_STRING(F32SYS);
    CHECK_FMT_STRING(F32);
#undef CHECK_FMT_STRING
    return 0;
}

int
SDL_GetNumAudioDrivers(void)
{
    return (SDL_arraysize(bootstrap) - 1);
}

const char *
SDL_GetAudioDriver(int index)
{
    if (index >= 0 && index < SDL_GetNumAudioDrivers()) {
        return (bootstrap[index]->name);
    }
    return (NULL);
}

int
SDL_AudioInit(const char *driver_name)
{
    int i = 0;
    int initialized = 0;
    int tried_to_init = 0;
    const char *envr = SDL_getenv("SDL_AUDIO_MUST_INIT_BUFFERS");

    must_init_callback_buffer = ((envr != NULL) && (SDL_atoi(envr)));

    if (SDL_WasInit(SDL_INIT_AUDIO)) {
        SDL_AudioQuit();        /* shutdown driver if already running. */
    }

    SDL_memset(&current_audio, '\0', sizeof(current_audio));
    SDL_memset(open_devices, '\0', sizeof(open_devices));

    /* Select the proper audio driver */
    if (driver_name == NULL) {
        driver_name = SDL_getenv("SDL_AUDIODRIVER");
    }

    for (i = 0; (!initialized) && (bootstrap[i]); ++i) {
        /* make sure we should even try this driver before doing so... */
        const AudioBootStrap *backend = bootstrap[i];
        if (((driver_name) && (SDL_strcasecmp(backend->name, driver_name))) ||
            ((!driver_name) && (backend->demand_only))) {
            continue;
        }

        tried_to_init = 1;
        SDL_memset(&current_audio, 0, sizeof(current_audio));
        current_audio.name = backend->name;
        current_audio.desc = backend->desc;
        initialized = backend->init(&current_audio.impl);
    }

    if (!initialized) {
        /* specific drivers will set the error message if they fail... */
        if (!tried_to_init) {
            if (driver_name) {
                SDL_SetError("%s not available", driver_name);
            } else {
                SDL_SetError("No available audio device");
            }
        }

        SDL_memset(&current_audio, 0, sizeof(current_audio));
        return (-1);            /* No driver was available, so fail. */
    }

    finalize_audio_entry_points();

    return (0);
}

/*
 * Get the current audio driver name
 */
const char *
SDL_GetCurrentAudioDriver()
{
    return current_audio.name;
}


int
SDL_GetNumAudioDevices(int iscapture)
{
    if (!SDL_WasInit(SDL_INIT_AUDIO)) {
        return -1;
    }
    if ((iscapture) && (!current_audio.impl.HasCaptureSupport)) {
        return 0;
    }

    if ((iscapture) && (current_audio.impl.OnlyHasDefaultInputDevice)) {
        return 1;
    }

    if ((!iscapture) && (current_audio.impl.OnlyHasDefaultOutputDevice)) {
        return 1;
    }

    return current_audio.impl.DetectDevices(iscapture);
}


const char *
SDL_GetAudioDeviceName(int index, int iscapture)
{
    if (!SDL_WasInit(SDL_INIT_AUDIO)) {
        SDL_SetError("Audio subsystem is not initialized");
        return NULL;
    }

    if ((iscapture) && (!current_audio.impl.HasCaptureSupport)) {
        SDL_SetError("No capture support");
        return NULL;
    }

    if (index < 0) {
        SDL_SetError("No such device");
        return NULL;
    }

    if ((iscapture) && (current_audio.impl.OnlyHasDefaultInputDevice)) {
        return DEFAULT_INPUT_DEVNAME;
    }

    if ((!iscapture) && (current_audio.impl.OnlyHasDefaultOutputDevice)) {
        return DEFAULT_OUTPUT_DEVNAME;
    }

    return current_audio.impl.GetDeviceName(index, iscapture);
}


static void
close_audio_device(SDL_AudioDevice * device)
{
    device->enabled = 0;
    if (device->thread != NULL) {
        SDL_WaitThread(device->thread, NULL);
    }
    if (device->mixer_lock != NULL) {
        SDL_DestroyMutex(device->mixer_lock);
    }
    if (device->fake_stream != NULL) {
        SDL_FreeAudioMem(device->fake_stream);
    }
    if (device->convert.needed) {
        SDL_FreeAudioMem(device->convert.buf);
    }
    if (device->opened) {
        current_audio.impl.CloseDevice(device);
        device->opened = 0;
    }
    SDL_FreeAudioMem(device);
}


/*
 * Sanity check desired AudioSpec for SDL_OpenAudio() in (orig).
 *  Fills in a sanitized copy in (prepared).
 *  Returns non-zero if okay, zero on fatal parameters in (orig).
 */
static int
prepare_audiospec(const SDL_AudioSpec * orig, SDL_AudioSpec * prepared)
{
    SDL_memcpy(prepared, orig, sizeof(SDL_AudioSpec));

    if (orig->callback == NULL) {
        SDL_SetError("SDL_OpenAudio() passed a NULL callback");
        return 0;
    }

    if (orig->freq == 0) {
        const char *env = SDL_getenv("SDL_AUDIO_FREQUENCY");
        if ((!env) || ((prepared->freq = SDL_atoi(env)) == 0)) {
            prepared->freq = 22050;     /* a reasonable default */
        }
    }

    if (orig->format == 0) {
        const char *env = SDL_getenv("SDL_AUDIO_FORMAT");
        if ((!env) || ((prepared->format = SDL_ParseAudioFormat(env)) == 0)) {
            prepared->format = AUDIO_S16;       /* a reasonable default */
        }
    }

    switch (orig->channels) {
    case 0:{
            const char *env = SDL_getenv("SDL_AUDIO_CHANNELS");
            if ((!env) || ((prepared->channels = (Uint8) SDL_atoi(env)) == 0)) {
                prepared->channels = 2; /* a reasonable default */
            }
            break;
        }
    case 1:                    /* Mono */
    case 2:                    /* Stereo */
    case 4:                    /* surround */
    case 6:                    /* surround with center and lfe */
        break;
    default:
        SDL_SetError("Unsupported number of audio channels.");
        return 0;
    }

    if (orig->samples == 0) {
        const char *env = SDL_getenv("SDL_AUDIO_SAMPLES");
        if ((!env) || ((prepared->samples = (Uint16) SDL_atoi(env)) == 0)) {
            /* Pick a default of ~46 ms at desired frequency */
            /* !!! FIXME: remove this when the non-Po2 resampling is in. */
            const int samples = (prepared->freq / 1000) * 46;
            int power2 = 1;
            while (power2 < samples) {
                power2 *= 2;
            }
            prepared->samples = power2;
        }
    }

    /* Calculate the silence and size of the audio specification */
    SDL_CalculateAudioSpec(prepared);

    return 1;
}


static SDL_AudioDeviceID
open_audio_device(const char *devname, int iscapture,
                  const SDL_AudioSpec * _desired, SDL_AudioSpec * obtained,
                  int min_id)
{
    SDL_AudioDeviceID id = 0;
    SDL_AudioSpec desired;
    SDL_AudioDevice *device;
    int i = 0;

    if (!SDL_WasInit(SDL_INIT_AUDIO)) {
        SDL_SetError("Audio subsystem is not initialized");
        return 0;
    }

    if ((iscapture) && (!current_audio.impl.HasCaptureSupport)) {
        SDL_SetError("No capture support");
        return 0;
    }

    if (!prepare_audiospec(_desired, &desired)) {
        return 0;
    }

    /* If app doesn't care about a specific device, let the user override. */
    if (devname == NULL) {
        devname = SDL_getenv("SDL_AUDIO_DEVICE_NAME");
    }

    /*
     * Catch device names at the high level for the simple case...
     * This lets us have a basic "device enumeration" for systems that
     *  don't have multiple devices, but makes sure the device name is
     *  always NULL when it hits the low level.
     *
     * Also make sure that the simple case prevents multiple simultaneous
     *  opens of the default system device.
     */

    if ((iscapture) && (current_audio.impl.OnlyHasDefaultInputDevice)) {
        if ((devname) && (SDL_strcmp(devname, DEFAULT_INPUT_DEVNAME) != 0)) {
            SDL_SetError("No such device");
            return 0;
        }
        devname = NULL;

        for (i = 0; i < SDL_arraysize(open_devices); i++) {
            if ((open_devices[i]) && (open_devices[i]->iscapture)) {
                SDL_SetError("Audio device already open");
                return 0;
            }
        }
    }

    if ((!iscapture) && (current_audio.impl.OnlyHasDefaultOutputDevice)) {
        if ((devname) && (SDL_strcmp(devname, DEFAULT_OUTPUT_DEVNAME) != 0)) {
            SDL_SetError("No such device");
            return 0;
        }
        devname = NULL;

        for (i = 0; i < SDL_arraysize(open_devices); i++) {
            if ((open_devices[i]) && (!open_devices[i]->iscapture)) {
                SDL_SetError("Audio device already open");
                return 0;
            }
        }
    }

    device = (SDL_AudioDevice *) SDL_AllocAudioMem(sizeof(SDL_AudioDevice));
    if (device == NULL) {
        SDL_OutOfMemory();
        return 0;
    }
    SDL_memset(device, '\0', sizeof(SDL_AudioDevice));
    SDL_memcpy(&device->spec, &desired, sizeof(SDL_AudioSpec));
    device->enabled = 1;
    device->paused = 1;
    device->iscapture = iscapture;

    /* Create a semaphore for locking the sound buffers */
    if (!current_audio.impl.SkipMixerLock) {
        device->mixer_lock = SDL_CreateMutex();
        if (device->mixer_lock == NULL) {
            close_audio_device(device);
            SDL_SetError("Couldn't create mixer lock");
            return 0;
        }
    }

    if (!current_audio.impl.OpenDevice(device, devname, iscapture)) {
        close_audio_device(device);
        return 0;
    }
    device->opened = 1;

    /* If the audio driver changes the buffer size, accept it */
    if (device->spec.samples != desired.samples) {
        desired.samples = device->spec.samples;
        SDL_CalculateAudioSpec(&device->spec);
    }

    /* Allocate a fake audio memory buffer */
    device->fake_stream = SDL_AllocAudioMem(device->spec.size);
    if (device->fake_stream == NULL) {
        close_audio_device(device);
        SDL_OutOfMemory();
        return 0;
    }

    /* See if we need to do any conversion */
    if (obtained != NULL) {
        SDL_memcpy(obtained, &device->spec, sizeof(SDL_AudioSpec));
    } else if (desired.freq != device->spec.freq ||
               desired.format != device->spec.format ||
               desired.channels != device->spec.channels) {
        /* Build an audio conversion block */
        if (SDL_BuildAudioCVT(&device->convert,
                              desired.format, desired.channels,
                              desired.freq,
                              device->spec.format, device->spec.channels,
                              device->spec.freq) < 0) {
            close_audio_device(device);
            return 0;
        }
        if (device->convert.needed) {
            device->convert.len = (int) (((double) desired.size) /
                                         device->convert.len_ratio);

            device->convert.buf =
                (Uint8 *) SDL_AllocAudioMem(device->convert.len *
                                            device->convert.len_mult);
            if (device->convert.buf == NULL) {
                close_audio_device(device);
                SDL_OutOfMemory();
                return 0;
            }
        }
    }

    /* Find an available device ID and store the structure... */
    for (id = min_id - 1; id < SDL_arraysize(open_devices); id++) {
        if (open_devices[id] == NULL) {
            open_devices[id] = device;
            break;
        }
    }

    if (id == SDL_arraysize(open_devices)) {
        SDL_SetError("Too many open audio devices");
        close_audio_device(device);
        return 0;
    }

    /* Start the audio thread if necessary */
    if (!current_audio.impl.ProvidesOwnCallbackThread) {
        /* Start the audio thread */
/* !!! FIXME: this is nasty. */
#if (defined(__WIN32__) && !defined(_WIN32_WCE)) && !defined(HAVE_LIBC)
#undef SDL_CreateThread
        device->thread = SDL_CreateThread(SDL_RunAudio, device, NULL, NULL);
#else
        device->thread = SDL_CreateThread(SDL_RunAudio, device);
#endif
        if (device->thread == NULL) {
            SDL_CloseAudioDevice(id + 1);
            SDL_SetError("Couldn't create audio thread");
            return 0;
        }
    }

    return id + 1;
}


int
SDL_OpenAudio(const SDL_AudioSpec * desired, SDL_AudioSpec * obtained)
{
    SDL_AudioDeviceID id = 0;

    /* Start up the audio driver, if necessary. This is legacy behaviour! */
    if (!SDL_WasInit(SDL_INIT_AUDIO)) {
        if (SDL_InitSubSystem(SDL_INIT_AUDIO) < 0) {
            return (-1);
        }
    }

    /* SDL_OpenAudio() is legacy and can only act on Device ID #1. */
    if (open_devices[0] != NULL) {
        SDL_SetError("Audio device is already opened");
        return (-1);
    }

    id = open_audio_device(NULL, 0, desired, obtained, 1);
    if (id > 1) {               /* this should never happen in theory... */
        SDL_CloseAudioDevice(id);
        SDL_SetError("Internal error"); /* MUST be Device ID #1! */
        return (-1);
    }

    return ((id == 0) ? -1 : 0);
}

SDL_AudioDeviceID
SDL_OpenAudioDevice(const char *device, int iscapture,
                    const SDL_AudioSpec * desired, SDL_AudioSpec * obtained)
{
    return open_audio_device(device, iscapture, desired, obtained, 2);
}

SDL_audiostatus
SDL_GetAudioDeviceStatus(SDL_AudioDeviceID devid)
{
    SDL_AudioDevice *device = get_audio_device(devid);
    SDL_audiostatus status = SDL_AUDIO_STOPPED;
    if (device && device->enabled) {
        if (device->paused) {
            status = SDL_AUDIO_PAUSED;
        } else {
            status = SDL_AUDIO_PLAYING;
        }
    }
    return (status);
}


SDL_audiostatus
SDL_GetAudioStatus(void)
{
    return SDL_GetAudioDeviceStatus(1);
}

void
SDL_PauseAudioDevice(SDL_AudioDeviceID devid, int pause_on)
{
    SDL_AudioDevice *device = get_audio_device(devid);
    if (device) {
        device->paused = pause_on;
    }
}

void
SDL_PauseAudio(int pause_on)
{
    SDL_PauseAudioDevice(1, pause_on);
}


void
SDL_LockAudioDevice(SDL_AudioDeviceID devid)
{
    /* Obtain a lock on the mixing buffers */
    SDL_AudioDevice *device = get_audio_device(devid);
    if (device) {
        current_audio.impl.LockDevice(device);
    }
}

void
SDL_LockAudio(void)
{
    SDL_LockAudioDevice(1);
}

void
SDL_UnlockAudioDevice(SDL_AudioDeviceID devid)
{
    /* Obtain a lock on the mixing buffers */
    SDL_AudioDevice *device = get_audio_device(devid);
    if (device) {
        current_audio.impl.UnlockDevice(device);
    }
}

void
SDL_UnlockAudio(void)
{
    SDL_UnlockAudioDevice(1);
}

void
SDL_CloseAudioDevice(SDL_AudioDeviceID devid)
{
    SDL_AudioDevice *device = get_audio_device(devid);
    if (device) {
        close_audio_device(device);
        open_devices[devid - 1] = NULL;
    }
}

void
SDL_CloseAudio(void)
{
    SDL_CloseAudioDevice(1);
}

void
SDL_AudioQuit(void)
{
    SDL_AudioDeviceID i;
    for (i = 0; i < SDL_arraysize(open_devices); i++) {
        SDL_CloseAudioDevice(i);
    }

    /* Free the driver data */
    current_audio.impl.Deinitialize();
    SDL_memset(&current_audio, '\0', sizeof(current_audio));
    SDL_memset(open_devices, '\0', sizeof(open_devices));
}

#define NUM_FORMATS 10
static int format_idx;
static int format_idx_sub;
static SDL_AudioFormat format_list[NUM_FORMATS][NUM_FORMATS] = {
    {AUDIO_U8, AUDIO_S8, AUDIO_S16LSB, AUDIO_S16MSB, AUDIO_U16LSB,
     AUDIO_U16MSB, AUDIO_S32LSB, AUDIO_S32MSB, AUDIO_F32LSB, AUDIO_F32MSB},
    {AUDIO_S8, AUDIO_U8, AUDIO_S16LSB, AUDIO_S16MSB, AUDIO_U16LSB,
     AUDIO_U16MSB, AUDIO_S32LSB, AUDIO_S32MSB, AUDIO_F32LSB, AUDIO_F32MSB},
    {AUDIO_S16LSB, AUDIO_S16MSB, AUDIO_U16LSB, AUDIO_U16MSB, AUDIO_S32LSB,
     AUDIO_S32MSB, AUDIO_F32LSB, AUDIO_F32MSB, AUDIO_U8, AUDIO_S8},
    {AUDIO_S16MSB, AUDIO_S16LSB, AUDIO_U16MSB, AUDIO_U16LSB, AUDIO_S32MSB,
     AUDIO_S32LSB, AUDIO_F32MSB, AUDIO_F32LSB, AUDIO_U8, AUDIO_S8},
    {AUDIO_U16LSB, AUDIO_U16MSB, AUDIO_S16LSB, AUDIO_S16MSB, AUDIO_S32LSB,
     AUDIO_S32MSB, AUDIO_F32LSB, AUDIO_F32MSB, AUDIO_U8, AUDIO_S8},
    {AUDIO_U16MSB, AUDIO_U16LSB, AUDIO_S16MSB, AUDIO_S16LSB, AUDIO_S32MSB,
     AUDIO_S32LSB, AUDIO_F32MSB, AUDIO_F32LSB, AUDIO_U8, AUDIO_S8},
    {AUDIO_S32LSB, AUDIO_S32MSB, AUDIO_F32LSB, AUDIO_F32MSB, AUDIO_S16LSB,
     AUDIO_S16MSB, AUDIO_U16LSB, AUDIO_U16MSB, AUDIO_U8, AUDIO_S8},
    {AUDIO_S32MSB, AUDIO_S32LSB, AUDIO_F32MSB, AUDIO_F32LSB, AUDIO_S16MSB,
     AUDIO_S16LSB, AUDIO_U16MSB, AUDIO_U16LSB, AUDIO_U8, AUDIO_S8},
    {AUDIO_F32LSB, AUDIO_F32MSB, AUDIO_S32LSB, AUDIO_S32MSB, AUDIO_S16LSB,
     AUDIO_S16MSB, AUDIO_U16LSB, AUDIO_U16MSB, AUDIO_U8, AUDIO_S8},
    {AUDIO_F32MSB, AUDIO_F32LSB, AUDIO_S32MSB, AUDIO_S32LSB, AUDIO_S16MSB,
     AUDIO_S16LSB, AUDIO_U16MSB, AUDIO_U16LSB, AUDIO_U8, AUDIO_S8},
};

SDL_AudioFormat
SDL_FirstAudioFormat(SDL_AudioFormat format)
{
    for (format_idx = 0; format_idx < NUM_FORMATS; ++format_idx) {
        if (format_list[format_idx][0] == format) {
            break;
        }
    }
    format_idx_sub = 0;
    return (SDL_NextAudioFormat());
}

SDL_AudioFormat
SDL_NextAudioFormat(void)
{
    if ((format_idx == NUM_FORMATS) || (format_idx_sub == NUM_FORMATS)) {
        return (0);
    }
    return (format_list[format_idx][format_idx_sub++]);
}

void
SDL_CalculateAudioSpec(SDL_AudioSpec * spec)
{
    switch (spec->format) {
    case AUDIO_U8:
        spec->silence = 0x80;
        break;
    default:
        spec->silence = 0x00;
        break;
    }
    spec->size = SDL_AUDIO_BITSIZE(spec->format) / 8;
    spec->size *= spec->channels;
    spec->size *= spec->samples;
}


/*
 * Moved here from SDL_mixer.c, since it relies on internals of an opened
 *  audio device (and is deprecated, by the way!).
 */
void
SDL_MixAudio(Uint8 * dst, const Uint8 * src, Uint32 len, int volume)
{
    /* Mix the user-level audio format */
    SDL_AudioDevice *device = get_audio_device(1);
    if (device != NULL) {
        SDL_AudioFormat format;
        if (device->convert.needed) {
            format = device->convert.src_format;
        } else {
            format = device->spec.format;
        }
        SDL_MixAudioFormat(dst, src, format, len, volume);
    }
}

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