src/audio/esd/SDL_esdaudio.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 an ESD network stream mixing buffer */

#include <sys/types.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <esd.h>

#include "SDL_timer.h"
#include "SDL_audio.h"
#include "../SDL_audiomem.h"
#include "../SDL_audio_c.h"
#include "../SDL_audiodev_c.h"
#include "SDL_esdaudio.h"

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

/* The tag name used by ESD audio */
#define ESD_DRIVER_NAME		"esd"

/* Audio driver functions */
static int ESD_OpenAudio(_THIS, SDL_AudioSpec * spec);
static void ESD_WaitAudio(_THIS);
static void ESD_PlayAudio(_THIS);
static Uint8 *ESD_GetAudioBuf(_THIS);
static void ESD_CloseAudio(_THIS);

#ifdef SDL_AUDIO_DRIVER_ESD_DYNAMIC

static const char *esd_library = SDL_AUDIO_DRIVER_ESD_DYNAMIC;
static void *esd_handle = NULL;
static int esd_loaded = 0;

static int (*SDL_NAME(esd_open_sound)) (const char *host);
static int (*SDL_NAME(esd_close)) (int esd);
static int (*SDL_NAME(esd_play_stream)) (esd_format_t format, int rate,
                                         const char *host, const char *name);
static struct
{
    const char *name;
    void **func;
} esd_functions[] = {
    {
    "esd_open_sound", (void **) &SDL_NAME(esd_open_sound)}, {
    "esd_close", (void **) &SDL_NAME(esd_close)}, {
"esd_play_stream", (void **) &SDL_NAME(esd_play_stream)},};

static void
UnloadESDLibrary()
{
    if (esd_loaded) {
        SDL_UnloadObject(esd_handle);
        esd_handle = NULL;
        esd_loaded = 0;
    }
}

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

    esd_handle = SDL_LoadObject(esd_library);
    if (esd_handle) {
        esd_loaded = 1;
        retval = 0;
        for (i = 0; i < SDL_arraysize(esd_functions); ++i) {
            *esd_functions[i].func =
                SDL_LoadFunction(esd_handle, esd_functions[i].name);
            if (!*esd_functions[i].func) {
                retval = -1;
                UnloadESDLibrary();
                break;
            }
        }
    }
    return retval;
}

#else

static void
UnloadESDLibrary()
{
    return;
}

static int
LoadESDLibrary(void)
{
    return 0;
}

#endif /* SDL_AUDIO_DRIVER_ESD_DYNAMIC */

/* Audio driver bootstrap functions */

static int
Audio_Available(void)
{
    int connection;
    int available;

    available = 0;
    if (LoadESDLibrary() < 0) {
        return available;
    }
    connection = SDL_NAME(esd_open_sound) (NULL);
    if (connection >= 0) {
        available = 1;
        SDL_NAME(esd_close) (connection);
    }
    UnloadESDLibrary();
    return (available);
}

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

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

    /* Initialize all variables that we clean on shutdown */
    LoadESDLibrary();
    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));
    audio_fd = -1;

    /* Set the function pointers */
    this->OpenAudio = ESD_OpenAudio;
    this->WaitAudio = ESD_WaitAudio;
    this->PlayAudio = ESD_PlayAudio;
    this->GetAudioBuf = ESD_GetAudioBuf;
    this->CloseAudio = ESD_CloseAudio;

    this->free = Audio_DeleteDevice;

    return this;
}

AudioBootStrap ESD_bootstrap = {
    ESD_DRIVER_NAME, "Enlightened Sound Daemon",
    Audio_Available, Audio_CreateDevice
};

/* This function waits until it is possible to write a full sound buffer */
static void
ESD_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
ESD_PlayAudio(_THIS)
{
    int written;

    /* Write the audio data, checking for EAGAIN on broken audio drivers */
    do {
        written = write(audio_fd, mixbuf, mixlen);
        if ((written < 0) && ((errno == 0) || (errno == EAGAIN))) {
            SDL_Delay(1);       /* Let a little CPU time go by */
        }
    }
    while ((written < 0) &&
           ((errno == 0) || (errno == EAGAIN) || (errno == EINTR)));

    /* Set the next write frame */
    next_frame += frame_ticks;

    /* If we couldn't write, assume fatal error for now */
    if (written < 0) {
        this->enabled = 0;
    }
}

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

static void
ESD_CloseAudio(_THIS)
{
    if (mixbuf != NULL) {
        SDL_FreeAudioMem(mixbuf);
        mixbuf = NULL;
    }
    if (audio_fd >= 0) {
        SDL_NAME(esd_close) (audio_fd);
        audio_fd = -1;
    }
}

/* Try to get the name of the program */
static char *
get_progname(void)
{
    char *progname = NULL;
#ifdef __LINUX__
    FILE *fp;
    static char temp[BUFSIZ];

    SDL_snprintf(temp, SDL_arraysize(temp), "/proc/%d/cmdline", getpid());
    fp = fopen(temp, "r");
    if (fp != NULL) {
        if (fgets(temp, sizeof(temp) - 1, fp)) {
            progname = SDL_strrchr(temp, '/');
            if (progname == NULL) {
                progname = temp;
            } else {
                progname = progname + 1;
            }
        }
        fclose(fp);
    }
#endif
    return (progname);
}

static int
ESD_OpenAudio(_THIS, SDL_AudioSpec * spec)
{
    esd_format_t format;

    /* Convert audio spec to the ESD audio format */
    format = (ESD_STREAM | ESD_PLAY);
    switch (spec->format & 0xFF) {
    case 8:
        format |= ESD_BITS8;
        break;
    case 16:
        format |= ESD_BITS16;
        break;
    default:
        SDL_SetError("Unsupported ESD audio format");
        return (-1);
    }
    if (spec->channels == 1) {
        format |= ESD_MONO;
    } else {
        format |= ESD_STEREO;
    }
#if 0
    spec->samples = ESD_BUF_SIZE;       /* Darn, no way to change this yet */
#endif

    /* Open a connection to the ESD audio server */
    audio_fd =
        SDL_NAME(esd_play_stream) (format, spec->freq, NULL, get_progname());
    if (audio_fd < 0) {
        SDL_SetError("Couldn't open ESD connection");
        return (-1);
    }

    /* Calculate the final parameters for this audio specification */
    SDL_CalculateAudioSpec(spec);
    frame_ticks = (float) (spec->samples * 1000) / spec->freq;
    next_frame = SDL_GetTicks() + frame_ticks;

    /* 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: */