view src/audio/disk/SDL_diskaudio.c @ 4001:6831b8723a85 SDL-1.2

Don't initialize the audio buffer passed to the application's audio callback, since they are expected to entirely fill it with data or silence. For legacy apps that might expect the buffer to already have silence and thus may not fill the buffer in the callback, there's an environment variable to expose the old behaviour. Fixes Bugzilla #416.
author Ryan C. Gordon <icculus@icculus.org>
date Thu, 05 Jul 2007 02:24:36 +0000
parents c439dad53df8
children 782fd950bd46 c121d94672cb a1b03ba2fcd0
line wrap: on
line source

/*
    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_OpenAudio(_THIS, SDL_AudioSpec *spec);
static void DISKAUD_WaitAudio(_THIS);
static void DISKAUD_PlayAudio(_THIS);
static Uint8 *DISKAUD_GetAudioBuf(_THIS);
static void DISKAUD_CloseAudio(_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)
{
	const char *envr = SDL_getenv("SDL_AUDIODRIVER");
	if (envr && (SDL_strcmp(envr, DISKAUD_DRIVER_NAME) == 0)) {
		return(1);
	}
	return(0);
}

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

static SDL_AudioDevice *DISKAUD_CreateDevice(int devindex)
{
	SDL_AudioDevice *this;
	const char *envr;

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

	envr = SDL_getenv(DISKENVR_WRITEDELAY);
	this->hidden->write_delay = (envr) ? SDL_atoi(envr) : DISKDEFAULT_WRITEDELAY;

	/* Set the function pointers */
	this->OpenAudio = DISKAUD_OpenAudio;
	this->WaitAudio = DISKAUD_WaitAudio;
	this->PlayAudio = DISKAUD_PlayAudio;
	this->GetAudioBuf = DISKAUD_GetAudioBuf;
	this->CloseAudio = DISKAUD_CloseAudio;

	this->free = DISKAUD_DeleteDevice;

	return this;
}

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

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

static void DISKAUD_PlayAudio(_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_GetAudioBuf(_THIS)
{
	return(this->hidden->mixbuf);
}

static void DISKAUD_CloseAudio(_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;
	}
}

static int DISKAUD_OpenAudio(_THIS, SDL_AudioSpec *spec)
{
	const char *fname = DISKAUD_GetOutputFilename();

	/* Open the audio device */
	this->hidden->output = SDL_RWFromFile(fname, "wb");
	if ( this->hidden->output == NULL ) {
		return(-1);
	}

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

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

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