SDL_dummyaudio.c
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/*
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
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This file written by Ryan C. Gordon (icculus@icculus.org)
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*/
#include "SDL_config.h"
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/* Output audio to nowhere... */
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#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_dummyaudio.h"
/* The tag name used by DUMMY audio */
#define DUMMYAUD_DRIVER_NAME "dummy"
/* Audio driver functions */
static int DUMMYAUD_OpenAudio(_THIS, SDL_AudioSpec *spec);
static void DUMMYAUD_WaitAudio(_THIS);
static void DUMMYAUD_PlayAudio(_THIS);
static Uint8 *DUMMYAUD_GetAudioBuf(_THIS);
static void DUMMYAUD_CloseAudio(_THIS);
/* Audio driver bootstrap functions */
static int DUMMYAUD_Available(void)
{
const char *envr = SDL_getenv("SDL_AUDIODRIVER");
if (envr && (SDL_strcmp(envr, DUMMYAUD_DRIVER_NAME) == 0)) {
return(1);
}
return(0);
}
static void DUMMYAUD_DeleteDevice(SDL_AudioDevice *device)
{
SDL_free(device->hidden);
SDL_free(device);
}
static SDL_AudioDevice *DUMMYAUD_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));
/* Set the function pointers */
this->OpenAudio = DUMMYAUD_OpenAudio;
this->WaitAudio = DUMMYAUD_WaitAudio;
this->PlayAudio = DUMMYAUD_PlayAudio;
this->GetAudioBuf = DUMMYAUD_GetAudioBuf;
this->CloseAudio = DUMMYAUD_CloseAudio;
this->free = DUMMYAUD_DeleteDevice;
return this;
}
AudioBootStrap DUMMYAUD_bootstrap = {
DUMMYAUD_DRIVER_NAME, "SDL dummy audio driver",
DUMMYAUD_Available, DUMMYAUD_CreateDevice
};
/* This function waits until it is possible to write a full sound buffer */
static void DUMMYAUD_WaitAudio(_THIS)
{
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/* Don't block on first calls to simulate initial fragment filling. */
if (this->hidden->initial_calls)
this->hidden->initial_calls--;
else
SDL_Delay(this->hidden->write_delay);
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}
static void DUMMYAUD_PlayAudio(_THIS)
{
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/* no-op...this is a null driver. */
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}
static Uint8 *DUMMYAUD_GetAudioBuf(_THIS)
{
return(this->hidden->mixbuf);
}
static void DUMMYAUD_CloseAudio(_THIS)
{
if ( this->hidden->mixbuf != NULL ) {
SDL_FreeAudioMem(this->hidden->mixbuf);
this->hidden->mixbuf = NULL;
}
}
static int DUMMYAUD_OpenAudio(_THIS, SDL_AudioSpec *spec)
{
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float bytes_per_sec = 0.0f;
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/* 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);
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bytes_per_sec = (float) (((spec->format & 0xFF) / 8) *
spec->channels * spec->freq);
/*
* We try to make this request more audio at the correct rate for
* a given audio spec, so timing stays fairly faithful.
* Also, we have it not block at all for the first two calls, so
* it seems like we're filling two audio fragments right out of the
* gate, like other SDL drivers tend to do.
*/
this->hidden->initial_calls = 2;
this->hidden->write_delay =
(Uint32) ((((float) spec->size) / bytes_per_sec) * 1000.0f);
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/* We're ready to rock and roll. :-) */
return(0);
}