dsl.c

来自「An interactive water fountain. A realis」· C语言 代码 · 共 281 行

/*
Copyright (C) 2003-2004 Ryan C. Gordon. and James Bentler

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program 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 General Public License for more details.

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

Originally written by Ryan C. Gordon. ([e-mail])
Adapted to work with JonoF's port by James Bentler ([e-mail])

*/
#include <stdlib.h>
#include <string.h>

#include "dsl.h"
#include "compat.h"
#include "pragmas.h"

#define _NEED_SDLMIXER	1
#include "sdl_inc.h"

extern int32_t MV_MixPage;

int32_t DSL_ErrorCode = DSL_Ok;

static int32_t mixer_initialized;
static int32_t interrupts_disabled = 0;

static int32_t(*_DSL_CallBackFunc)(int32_t);
static volatile char *_DSL_BufferStart;
static int32_t _DSL_BufferSize;
static int32_t _DSL_SampleRate;
static int32_t _DSL_remainder;
static Uint16 _DSL_format;
static int32_t _DSL_channels;


static Mix_Chunk *blank;
static uint8_t *blank_buf;

/*
possible todo ideas: cache sdl/sdl mixer error messages.
*/

char *DSL_ErrorString(int32_t ErrorNumber)
{
    char *ErrorString;

    switch (ErrorNumber)
    {
    case DSL_Warning:
    case DSL_Error:
        ErrorString = DSL_ErrorString(DSL_ErrorCode);
        break;

    case DSL_Ok:
        ErrorString = "SDL Driver ok.";
        break;

    case DSL_SDLInitFailure:
        ErrorString = "SDL Audio initialization failed.";
        break;

    case DSL_MixerActive:
        ErrorString = "SDL Mixer already initialized.";
        break;

    case DSL_MixerInitFailure:
        ErrorString = "SDL Mixer initialization failed.";
        break;

    default:
        ErrorString = "Unknown SDL Driver error.";
        break;
    }

    return ErrorString;
}

static void DSL_SetErrorCode(int32_t ErrorCode)
{
    DSL_ErrorCode = ErrorCode;
}

int32_t DSL_Init(int32_t soundcard, int32_t mixrate, int32_t numchannels, int32_t samplebits, int32_t buffersize)
{
    /* FIXME: Do I need an SDL_mixer version check
     * like that in sdlmusic.h here, too???
     */

    UNREFERENCED_PARAMETER(soundcard);
    UNREFERENCED_PARAMETER(buffersize);

    DSL_SetErrorCode(DSL_Ok);

    if (SDL_InitSubSystem(SDL_INIT_AUDIO) < 0)
    {
        DSL_SetErrorCode(DSL_SDLInitFailure);

        return DSL_Error;
    }

    _DSL_channels = numchannels;
    _DSL_SampleRate = mixrate;
    _DSL_format = (samplebits == 16) ? AUDIO_S16SYS : AUDIO_U8;

    return DSL_Ok;
}

void DSL_Shutdown(void)
{
    DSL_StopPlayback();
}

static void mixer_callback(int32_t chan, void *stream, int32_t len, void *udata)
{
    Uint8 *stptr;
    Uint8 *fxptr;
    int32_t copysize;
    UNREFERENCED_PARAMETER(chan);
    UNREFERENCED_PARAMETER(udata);
    /* len should equal _DSL_BufferSize, else this is screwed up */

    stptr = (Uint8 *)stream;

    if (_DSL_remainder > 0)
    {
        copysize = min(len, _DSL_remainder);

        fxptr = (Uint8 *)(&_DSL_BufferStart[MV_MixPage *
                                        _DSL_BufferSize]);

        memcpy(stptr, fxptr+(_DSL_BufferSize-_DSL_remainder), copysize);

        len -= copysize;
        _DSL_remainder -= copysize;

        stptr += copysize;
    }

    while (len > 0)
    {
        /* new buffer */

        _DSL_CallBackFunc(0);

        fxptr = (Uint8 *)(&_DSL_BufferStart[MV_MixPage *
                                        _DSL_BufferSize]);

        copysize = min(len, _DSL_BufferSize);

        memcpy(stptr, fxptr, copysize);

        len -= copysize;

        stptr += copysize;
    }

    _DSL_remainder = len;
}

//int32_t   DSL_BeginBufferedPlayback(char *BufferStart,
  //                              int32_t BufferSize, int32_t NumDivisions, unsigned SampleRate,
    //                            int32_t MixMode, void(*CallBackFunc)(void))
int32_t DSL_BeginBufferedPlayback(char *BufferStart, int32_t(*CallBackFunc)(int32_t), int32_t BufferSize, int32_t NumDivisions)
{
    int32_t chunksize;

    if (mixer_initialized)
    {
        DSL_SetErrorCode(DSL_MixerActive);

        return DSL_Error;
    }

    _DSL_CallBackFunc = CallBackFunc;
    _DSL_BufferStart = BufferStart;
    _DSL_BufferSize = (BufferSize / NumDivisions);
    
    _DSL_remainder = 0;

    /*
       23ms is typically ideal (11025,22050,44100)
       46ms isn't bad
    */

    chunksize = 512;

    if (_DSL_SampleRate >= 16000) chunksize *= 2;
    if (_DSL_SampleRate >= 32000) chunksize *= 2;

    if (Mix_OpenAudio(_DSL_SampleRate, _DSL_format, _DSL_channels, chunksize) < 0)
    {
        DSL_SetErrorCode(DSL_MixerInitFailure);

        return DSL_Error;
    }

    /*
       Mix_SetPostMix(mixer_callback, NULL);
    */
    /* have to use a channel because postmix will overwrite the music... */
    Mix_RegisterEffect(0, mixer_callback, NULL, NULL);

    /* create a dummy sample just to allocate that channel */
    blank_buf = (Uint8 *)malloc(4096);
    memset(blank_buf, 0, 4096);

    blank = Mix_QuickLoad_RAW(blank_buf, 4096);

    Mix_PlayChannel(0, blank, -1);

    mixer_initialized = 1;

    return DSL_Ok;
}

void DSL_StopPlayback(void)
{
    if (mixer_initialized)
    {
        Mix_HaltChannel(0);
    }

    if (blank != NULL)
    {
        Mix_FreeChunk(blank);
    }

    blank = NULL;

    if (blank_buf  != NULL)
    {
        free(blank_buf);
    }

    blank_buf = NULL;

    if (mixer_initialized)
    {
        Mix_CloseAudio();
    }

    mixer_initialized = 0;
}

unsigned DSL_GetPlaybackRate(void)
{
    return _DSL_SampleRate;
}

int32_t DisableInterrupts(void)
{
    if (interrupts_disabled++)
        return 0;
//    interrupts_disabled = 1;
    SDL_LockAudio();
    return(0);
}

int32_t RestoreInterrupts(int32_t flags)
{
    UNREFERENCED_PARAMETER(flags);
    if (--interrupts_disabled)
        return 0;
//   interrupts_disabled = 0;
    SDL_UnlockAudio();
    return(0);
}