src/audio/alsa/SDL_alsa_audio.c

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2004 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 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
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

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

/* Allow access to a raw mixing buffer */

#include <sys/types.h>
#include <signal.h>             /* For kill() */

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

#ifdef SDL_AUDIO_DRIVER_ALSA_DYNAMIC
#include <dlfcn.h>
#include "SDL_name.h"
#include "SDL_loadso.h"
#else
#define SDL_NAME(X)	X
#endif


/* The tag name used by ALSA audio */
#define DRIVER_NAME         "alsa"

/* The default ALSA audio driver */
#define DEFAULT_DEVICE	"default"

/* Audio driver functions */
static int ALSA_OpenAudio (_THIS, SDL_AudioSpec * spec);
static void ALSA_WaitAudio (_THIS);
static void ALSA_PlayAudio (_THIS);
static Uint8 *ALSA_GetAudioBuf (_THIS);
static void ALSA_CloseAudio (_THIS);

#ifdef SDL_AUDIO_DRIVER_ALSA_DYNAMIC

static const char *alsa_library = SDL_AUDIO_DRIVER_ALSA_DYNAMIC;
static void *alsa_handle = NULL;
static int alsa_loaded = 0;

static int (*SDL_snd_pcm_open) (snd_pcm_t ** pcm, const char *name,
                                snd_pcm_stream_t stream, int mode);
static int (*SDL_NAME (snd_pcm_open)) (snd_pcm_t ** pcm, const char *name,
                                       snd_pcm_stream_t stream, int mode);
static int (*SDL_NAME (snd_pcm_close)) (snd_pcm_t * pcm);
static snd_pcm_sframes_t (*SDL_NAME (snd_pcm_writei)) (snd_pcm_t * pcm,
                                                       const void *buffer,
                                                       snd_pcm_uframes_t
                                                       size);
static int (*SDL_NAME (snd_pcm_resume)) (snd_pcm_t * pcm);
static int (*SDL_NAME (snd_pcm_prepare)) (snd_pcm_t * pcm);
static int (*SDL_NAME (snd_pcm_drain)) (snd_pcm_t * pcm);
static const char *(*SDL_NAME (snd_strerror)) (int errnum);
static size_t (*SDL_NAME (snd_pcm_hw_params_sizeof)) (void);
static size_t (*SDL_NAME (snd_pcm_sw_params_sizeof)) (void);
static int (*SDL_NAME (snd_pcm_hw_params_any)) (snd_pcm_t * pcm,
                                                snd_pcm_hw_params_t * params);
static int (*SDL_NAME (snd_pcm_hw_params_set_access)) (snd_pcm_t * pcm,
                                                       snd_pcm_hw_params_t *
                                                       params,
                                                       snd_pcm_access_t
                                                       access);
static int (*SDL_NAME (snd_pcm_hw_params_set_format)) (snd_pcm_t * pcm,
                                                       snd_pcm_hw_params_t *
                                                       params,
                                                       snd_pcm_format_t val);
static int (*SDL_NAME (snd_pcm_hw_params_set_channels)) (snd_pcm_t * pcm,
                                                         snd_pcm_hw_params_t *
                                                         params,
                                                         unsigned int val);
static int (*SDL_NAME (snd_pcm_hw_params_get_channels)) (const
                                                         snd_pcm_hw_params_t *
                                                         params);
static unsigned int
    (*SDL_NAME (snd_pcm_hw_params_set_rate_near)) (snd_pcm_t *
                                                   pcm,
                                                   snd_pcm_hw_params_t
                                                   * params,
                                                   unsigned
                                                   int val, int *dir);
static snd_pcm_uframes_t
    (*SDL_NAME (snd_pcm_hw_params_set_period_size_near)) (snd_pcm_t * pcm,
                                                          snd_pcm_hw_params_t
                                                          * params,
                                                          snd_pcm_uframes_t
                                                          val, int *dir);
static snd_pcm_sframes_t
    (*SDL_NAME (snd_pcm_hw_params_get_period_size)) (const
                                                     snd_pcm_hw_params_t
                                                     * params);
static unsigned int
    (*SDL_NAME (snd_pcm_hw_params_set_periods_near)) (snd_pcm_t * pcm,
                                                      snd_pcm_hw_params_t
                                                      * params,
                                                      unsigned int val,
                                                      int *dir);
static int (*SDL_NAME (snd_pcm_hw_params_get_periods)) (snd_pcm_hw_params_t *
                                                        params);
static int (*SDL_NAME (snd_pcm_hw_params)) (snd_pcm_t * pcm,
                                            snd_pcm_hw_params_t * params);
/*
*/
static int (*SDL_NAME (snd_pcm_sw_params_current)) (snd_pcm_t * pcm,
                                                    snd_pcm_sw_params_t *
                                                    swparams);
static int (*SDL_NAME (snd_pcm_sw_params_set_start_threshold)) (snd_pcm_t *
                                                                pcm,
                                                                snd_pcm_sw_params_t
                                                                * params,
                                                                snd_pcm_uframes_t
                                                                val);
static int (*SDL_NAME (snd_pcm_sw_params_set_avail_min)) (snd_pcm_t * pcm,
                                                          snd_pcm_sw_params_t
                                                          * params,
                                                          snd_pcm_uframes_t
                                                          val);
static int (*SDL_NAME (snd_pcm_sw_params)) (snd_pcm_t * pcm,
                                            snd_pcm_sw_params_t * params);
static int (*SDL_NAME (snd_pcm_nonblock)) (snd_pcm_t * pcm, int nonblock);
#define snd_pcm_hw_params_sizeof SDL_NAME(snd_pcm_hw_params_sizeof)
#define snd_pcm_sw_params_sizeof SDL_NAME(snd_pcm_sw_params_sizeof)

/* cast funcs to char* first, to please GCC's strict aliasing rules. */
static struct
{
    const char *name;
    void **func;
} alsa_functions[] = {
    {
    "snd_pcm_open", (void **) (char *) &SDL_NAME (snd_pcm_open)}, {
    "snd_pcm_close", (void **) (char *) &SDL_NAME (snd_pcm_close)}, {
    "snd_pcm_writei", (void **) (char *) &SDL_NAME (snd_pcm_writei)}, {
    "snd_pcm_resume", (void **) (char *) &SDL_NAME (snd_pcm_resume)}, {
    "snd_pcm_prepare", (void **) (char *) &SDL_NAME (snd_pcm_prepare)}, {
    "snd_pcm_drain", (void **) (char *) &SDL_NAME (snd_pcm_drain)}, {
    "snd_strerror", (void **) (char *) &SDL_NAME (snd_strerror)}, {
    "snd_pcm_hw_params_sizeof",
            (void **) (char *) &SDL_NAME (snd_pcm_hw_params_sizeof)}, {
    "snd_pcm_sw_params_sizeof",
            (void **) (char *) &SDL_NAME (snd_pcm_sw_params_sizeof)}, {
    "snd_pcm_hw_params_any",
            (void **) (char *) &SDL_NAME (snd_pcm_hw_params_any)}, {
    "snd_pcm_hw_params_set_access",
            (void **) (char *) &SDL_NAME (snd_pcm_hw_params_set_access)}, {
    "snd_pcm_hw_params_set_format",
            (void **) (char *) &SDL_NAME (snd_pcm_hw_params_set_format)}, {
    "snd_pcm_hw_params_set_channels",
            (void **) (char *) &SDL_NAME (snd_pcm_hw_params_set_channels)}, {
    "snd_pcm_hw_params_get_channels",
            (void **) (char *) &SDL_NAME (snd_pcm_hw_params_get_channels)}, {
    "snd_pcm_hw_params_set_rate_near",
            (void **) (char *) &SDL_NAME (snd_pcm_hw_params_set_rate_near)}, {
        "snd_pcm_hw_params_set_period_size_near", (void **) (char *)
    &SDL_NAME (snd_pcm_hw_params_set_period_size_near)}, {
    "snd_pcm_hw_params_get_period_size",
            (void **) (char *) &SDL_NAME (snd_pcm_hw_params_get_period_size)},
    {
        "snd_pcm_hw_params_set_periods_near", (void **) (char *)
    &SDL_NAME (snd_pcm_hw_params_set_periods_near)}, {
    "snd_pcm_hw_params_get_periods",
            (void **) (char *) &SDL_NAME (snd_pcm_hw_params_get_periods)}, {
    "snd_pcm_hw_params", (void **) (char *) &SDL_NAME (snd_pcm_hw_params)}, {
    "snd_pcm_sw_params_current",
            (void **) (char *) &SDL_NAME (snd_pcm_sw_params_current)}, {
        "snd_pcm_sw_params_set_start_threshold", (void **) (char *)
    &SDL_NAME (snd_pcm_sw_params_set_start_threshold)}, {
    "snd_pcm_sw_params_set_avail_min",
            (void **) (char *) &SDL_NAME (snd_pcm_sw_params_set_avail_min)}, {
    "snd_pcm_sw_params", (void **) (char *) &SDL_NAME (snd_pcm_sw_params)}, {
"snd_pcm_nonblock", (void **) (char *) &SDL_NAME (snd_pcm_nonblock)},};

static void
UnloadALSALibrary (void)
{
    if (alsa_loaded) {
/*		SDL_UnloadObject(alsa_handle);*/
        dlclose (alsa_handle);
        alsa_handle = NULL;
        alsa_loaded = 0;
    }
}

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

/*	alsa_handle = SDL_LoadObject(alsa_library);*/
    alsa_handle = dlopen (alsa_library, RTLD_NOW);
    if (alsa_handle) {
        alsa_loaded = 1;
        retval = 0;
        for (i = 0; i < SDL_arraysize (alsa_functions); i++) {
/*			*alsa_functions[i].func = SDL_LoadFunction(alsa_handle,alsa_functions[i].name);*/
#if HAVE_DLVSYM
            *alsa_functions[i].func =
                dlvsym (alsa_handle, alsa_functions[i].name, "ALSA_0.9");
            if (!*alsa_functions[i].func)
#endif
                *alsa_functions[i].func =
                    dlsym (alsa_handle, alsa_functions[i].name);
            if (!*alsa_functions[i].func) {
                retval = -1;
                UnloadALSALibrary ();
                break;
            }
        }
    }
    return retval;
}

#else

static void
UnloadALSALibrary (void)
{
    return;
}

static int
LoadALSALibrary (void)
{
    return 0;
}

#endif /* SDL_AUDIO_DRIVER_ALSA_DYNAMIC */

static const char *
get_audio_device (int channels)
{
    const char *device;

    device = SDL_getenv ("AUDIODEV");   /* Is there a standard variable name? */
    if (device == NULL) {
        if (channels == 6)
            device = "surround51";
        else if (channels == 4)
            device = "surround40";
        else
            device = DEFAULT_DEVICE;
    }
    return device;
}

/* Audio driver bootstrap functions */

static int
Audio_Available (void)
{
    int available;
    int status;
    snd_pcm_t *handle;

    available = 0;
    if (LoadALSALibrary () < 0) {
        return available;
    }
    status =
        SDL_NAME (snd_pcm_open) (&handle, get_audio_device (2),
                                 SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
    if (status >= 0) {
        available = 1;
        SDL_NAME (snd_pcm_close) (handle);
    }
    UnloadALSALibrary ();
    return (available);
}

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

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

    /* Initialize all variables that we clean on shutdown */
    LoadALSALibrary ();
    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));

    /* Set the function pointers */
    this->OpenAudio = ALSA_OpenAudio;
    this->WaitAudio = ALSA_WaitAudio;
    this->PlayAudio = ALSA_PlayAudio;
    this->GetAudioBuf = ALSA_GetAudioBuf;
    this->CloseAudio = ALSA_CloseAudio;

    this->free = Audio_DeleteDevice;

    return this;
}

AudioBootStrap ALSA_bootstrap = {
    DRIVER_NAME, "ALSA 0.9 PCM audio",
    Audio_Available, Audio_CreateDevice
};

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

static void
ALSA_PlayAudio (_THIS)
{
    int status;
    int sample_len;
    signed short *sample_buf;

    sample_len = this->spec.samples;
    sample_buf = (signed short *) mixbuf;
    while (sample_len > 0) {
        status =
            SDL_NAME (snd_pcm_writei) (pcm_handle, sample_buf, sample_len);
        if (status < 0) {
            if (status == -EAGAIN) {
                SDL_Delay (1);
                continue;
            }
            if (status == -ESTRPIPE) {
                do {
                    SDL_Delay (1);
                    status = SDL_NAME (snd_pcm_resume) (pcm_handle);
                }
                while (status == -EAGAIN);
            }
            if (status < 0) {
                status = SDL_NAME (snd_pcm_prepare) (pcm_handle);
            }
            if (status < 0) {
                /* Hmm, not much we can do - abort */
                this->enabled = 0;
                return;
            }
            continue;
        }
        sample_buf += status * this->spec.channels;
        sample_len -= status;
    }
}

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

static void
ALSA_CloseAudio (_THIS)
{
    if (mixbuf != NULL) {
        SDL_FreeAudioMem (mixbuf);
        mixbuf = NULL;
    }
    if (pcm_handle) {
        SDL_NAME (snd_pcm_drain) (pcm_handle);
        SDL_NAME (snd_pcm_close) (pcm_handle);
        pcm_handle = NULL;
    }
}

static int
ALSA_OpenAudio (_THIS, SDL_AudioSpec * spec)
{
    int status;
    snd_pcm_hw_params_t *hwparams;
    snd_pcm_sw_params_t *swparams;
    snd_pcm_format_t format;
    snd_pcm_uframes_t frames;
    Uint16 test_format;

    /* Open the audio device */
    /* Name of device should depend on # channels in spec */
    status =
        SDL_NAME (snd_pcm_open) (&pcm_handle,
                                 get_audio_device (spec->channels),
                                 SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);

    if (status < 0) {
        SDL_SetError ("Couldn't open audio device: %s",
                      SDL_NAME (snd_strerror) (status));
        return (-1);
    }

    /* Figure out what the hardware is capable of */
    snd_pcm_hw_params_alloca (&hwparams);
    status = SDL_NAME (snd_pcm_hw_params_any) (pcm_handle, hwparams);
    if (status < 0) {
        SDL_SetError ("Couldn't get hardware config: %s",
                      SDL_NAME (snd_strerror) (status));
        ALSA_CloseAudio (this);
        return (-1);
    }

    /* SDL only uses interleaved sample output */
    status =
        SDL_NAME (snd_pcm_hw_params_set_access) (pcm_handle, hwparams,
                                                 SND_PCM_ACCESS_RW_INTERLEAVED);
    if (status < 0) {
        SDL_SetError ("Couldn't set interleaved access: %s",
                      SDL_NAME (snd_strerror) (status));
        ALSA_CloseAudio (this);
        return (-1);
    }

    /* Try for a closest match on audio format */
    status = -1;
    for (test_format = SDL_FirstAudioFormat (spec->format);
         test_format && (status < 0);) {
        switch (test_format) {
        case AUDIO_U8:
            format = SND_PCM_FORMAT_U8;
            break;
        case AUDIO_S8:
            format = SND_PCM_FORMAT_S8;
            break;
        case AUDIO_S16LSB:
            format = SND_PCM_FORMAT_S16_LE;
            break;
        case AUDIO_S16MSB:
            format = SND_PCM_FORMAT_S16_BE;
            break;
        case AUDIO_U16LSB:
            format = SND_PCM_FORMAT_U16_LE;
            break;
        case AUDIO_U16MSB:
            format = SND_PCM_FORMAT_U16_BE;
            break;
        default:
            format = 0;
            break;
        }
        if (format != 0) {
            status =
                SDL_NAME (snd_pcm_hw_params_set_format) (pcm_handle,
                                                         hwparams, format);
        }
        if (status < 0) {
            test_format = SDL_NextAudioFormat ();
        }
    }
    if (status < 0) {
        SDL_SetError ("Couldn't find any hardware audio formats");
        ALSA_CloseAudio (this);
        return (-1);
    }
    spec->format = test_format;

    /* Set the number of channels */
    status =
        SDL_NAME (snd_pcm_hw_params_set_channels) (pcm_handle, hwparams,
                                                   spec->channels);
    if (status < 0) {
        status = SDL_NAME (snd_pcm_hw_params_get_channels) (hwparams);
        if ((status <= 0) || (status > 2)) {
            SDL_SetError ("Couldn't set audio channels");
            ALSA_CloseAudio (this);
            return (-1);
        }
        spec->channels = status;
    }

    /* Set the audio rate */
    status =
        SDL_NAME (snd_pcm_hw_params_set_rate_near) (pcm_handle, hwparams,
                                                    spec->freq, NULL);
    if (status < 0) {
        SDL_SetError ("Couldn't set audio frequency: %s",
                      SDL_NAME (snd_strerror) (status));
        ALSA_CloseAudio (this);
        return (-1);
    }
    spec->freq = status;

    /* Set the buffer size, in samples */
    frames = spec->samples;
    frames =
        SDL_NAME (snd_pcm_hw_params_set_period_size_near) (pcm_handle,
                                                           hwparams, frames,
                                                           NULL);
    spec->samples = frames;
    SDL_NAME (snd_pcm_hw_params_set_periods_near) (pcm_handle, hwparams, 2,
                                                   NULL);

    /* "set" the hardware with the desired parameters */
    status = SDL_NAME (snd_pcm_hw_params) (pcm_handle, hwparams);
    if (status < 0) {
        SDL_SetError ("Couldn't set hardware audio parameters: %s",
                      SDL_NAME (snd_strerror) (status));
        ALSA_CloseAudio (this);
        return (-1);
    }

/* This is useful for debugging... */
/*
{ snd_pcm_sframes_t bufsize; int fragments;
   bufsize = SDL_NAME(snd_pcm_hw_params_get_period_size)(hwparams);
   fragments = SDL_NAME(snd_pcm_hw_params_get_periods)(hwparams);

   fprintf(stderr, "ALSA: bufsize = %ld, fragments = %d\n", bufsize, fragments);
}
*/

    /* Set the software parameters */
    snd_pcm_sw_params_alloca (&swparams);
    status = SDL_NAME (snd_pcm_sw_params_current) (pcm_handle, swparams);
    if (status < 0) {
        SDL_SetError ("Couldn't get software config: %s",
                      SDL_NAME (snd_strerror) (status));
        ALSA_CloseAudio (this);
        return (-1);
    }
    status =
        SDL_NAME (snd_pcm_sw_params_set_start_threshold) (pcm_handle,
                                                          swparams, 0);
    if (status < 0) {
        SDL_SetError ("Couldn't set start threshold: %s",
                      SDL_NAME (snd_strerror) (status));
        ALSA_CloseAudio (this);
        return (-1);
    }
    status =
        SDL_NAME (snd_pcm_sw_params_set_avail_min) (pcm_handle, swparams,
                                                    frames);
    if (status < 0) {
        SDL_SetError ("Couldn't set avail min: %s",
                      SDL_NAME (snd_strerror) (status));
        ALSA_CloseAudio (this);
        return (-1);
    }
    status = SDL_NAME (snd_pcm_sw_params) (pcm_handle, swparams);
    if (status < 0) {
        SDL_SetError ("Couldn't set software audio parameters: %s",
                      SDL_NAME (snd_strerror) (status));
        ALSA_CloseAudio (this);
        return (-1);
    }

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

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

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

    /* Switch to blocking mode for playback */
    SDL_NAME (snd_pcm_nonblock) (pcm_handle, 0);

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

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