src/audio/disk/SDL_diskaudio.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

    This file written by Ryan C. Gordon (icculus@icculus.org)
*/
#include "SDL_config.h"

/* Output raw audio data to a file. */

#if HAVE_STDIO_H
#include <stdio.h>
#endif

#include "SDL_rwops.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_diskaudio.h"

/* The tag name used by DISK audio */
#define DISKAUD_DRIVER_NAME         "disk"

/* environment variables and defaults. */
#define DISKENVR_OUTFILE         "SDL_DISKAUDIOFILE"
#define DISKDEFAULT_OUTFILE      "sdlaudio.raw"
#define DISKENVR_WRITEDELAY      "SDL_DISKAUDIODELAY"
#define DISKDEFAULT_WRITEDELAY   150

/* Audio driver functions */
static int DISKAUD_OpenDevice(_THIS, const char *devname, int iscapture);
static void DISKAUD_WaitDevice(_THIS);
static void DISKAUD_PlayDevice(_THIS);
static Uint8 *DISKAUD_GetDeviceBuf(_THIS);
static void DISKAUD_CloseDevice(_THIS);

static const char *
DISKAUD_GetOutputFilename(void)
{
    const char *envr = SDL_getenv(DISKENVR_OUTFILE);
    return ((envr != NULL) ? envr : DISKDEFAULT_OUTFILE);
}

/* Audio driver bootstrap functions */
static int
DISKAUD_Available(void)
{
    /* !!! FIXME: check this at a higher level... */
    /* only ever use this driver if explicitly requested. */
    const char *envr = SDL_getenv("SDL_AUDIODRIVER");
    if (envr && (SDL_strcasecmp(envr, DISKAUD_DRIVER_NAME) == 0)) {
        return (1);
    }
    return (0);
}

static int
DISKAUD_Init(SDL_AudioDriverImpl *impl)
{
    /* Initialize all variables that we clean on shutdown */
    SDL_memset(impl, '\0', sizeof (SDL_AudioDriverImpl));

    /* Set the function pointers */
    impl->OpenDevice = DISKAUD_OpenDevice;
    impl->WaitDevice = DISKAUD_WaitDevice;
    impl->PlayDevice = DISKAUD_PlayDevice;
    impl->GetDeviceBuf = DISKAUD_GetDeviceBuf;
    impl->CloseDevice = DISKAUD_CloseDevice;

    return 1;
}

AudioBootStrap DISKAUD_bootstrap = {
    DISKAUD_DRIVER_NAME, "direct-to-disk audio",
    DISKAUD_Available, DISKAUD_Init
};

/* This function waits until it is possible to write a full sound buffer */
static void
DISKAUD_WaitDevice(_THIS)
{
    SDL_Delay(this->hidden->write_delay);
}

static void
DISKAUD_PlayDevice(_THIS)
{
    int written;

    /* Write the audio data */
    written = SDL_RWwrite(this->hidden->output,
                          this->hidden->mixbuf, 1, this->hidden->mixlen);

    /* If we couldn't write, assume fatal error for now */
    if ((Uint32) written != this->hidden->mixlen) {
        this->enabled = 0;
    }
#ifdef DEBUG_AUDIO
    fprintf(stderr, "Wrote %d bytes of audio data\n", written);
#endif
}

static Uint8 *
DISKAUD_GetDeviceBuf(_THIS)
{
    return (this->hidden->mixbuf);
}

static void
DISKAUD_CloseDevice(_THIS)
{
    if (this->hidden->mixbuf != NULL) {
        SDL_FreeAudioMem(this->hidden->mixbuf);
        this->hidden->mixbuf = NULL;
    }
    if (this->hidden->output != NULL) {
        SDL_RWclose(this->hidden->output);
        this->hidden->output = NULL;
    }
    SDL_free(this->hidden);
    this->hidden = NULL;
}

static int
DISKAUD_OpenDevice(_THIS, const char *devname, int iscapture)
{
    const char *envr = SDL_getenv(DISKENVR_WRITEDELAY);
    const char *fname = DISKAUD_GetOutputFilename();

    /* !!! FIXME: use device name for non-default filename? */
    if (devname != NULL) {
        SDL_SetError("Disk audio device name must be NULL");
        return 0;
    }

    this->hidden = (struct SDL_PrivateAudioData *)
            SDL_malloc(sizeof (*this->hidden));
    if (this->hidden == NULL) {
        SDL_OutOfMemory();
        return 0;
    }
    SDL_memset(this->hidden, 0, sizeof (*this->hidden));

    /* Open the audio device */
    this->hidden->output = SDL_RWFromFile(fname, "wb");
    if (this->hidden->output == NULL) {
        DISKAUD_CloseDevice(this);
        return 0;
    }

    /* Allocate mixing buffer */
    this->hidden->mixbuf = (Uint8 *) SDL_AllocAudioMem(this->hidden->mixlen);
    if (this->hidden->mixbuf == NULL) {
        DISKAUD_CloseDevice(this);
        return 0;
    }
    SDL_memset(this->hidden->mixbuf, this->spec.silence, this->spec.size);

    this->hidden->mixlen = this->spec.size;
    this->hidden->write_delay =
        (envr) ? SDL_atoi(envr) : DISKDEFAULT_WRITEDELAY;

#if HAVE_STDIO_H
    fprintf(stderr,
            "WARNING: You are using the SDL disk writer audio driver!\n"
            " Writing to file [%s].\n", fname);
#endif

    /* We're ready to rock and roll. :-) */
    return 1;
}

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