sdl_mintaudio.c

SDL库 在进行视频显示程序spcaview安装时必须的库文件

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2004 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 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
    Library General Public License for more details.

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

    Sam Lantinga
    [e-mail]
*/
#include "SDL_config.h"

/*
	Audio interrupt variables and callback function

	Patrice Mandin
*/

#include <unistd.h>

#include <mint/osbind.h>
#include <mint/falcon.h>
#include <mint/mintbind.h>
#include <mint/cookie.h>

#include "SDL_audio.h"
#include "SDL_mintaudio.h"
#include "SDL_mintaudio_stfa.h"

/* The audio device */

SDL_AudioDevice *SDL_MintAudio_device;
Uint8 *SDL_MintAudio_audiobuf[2];	/* Pointers to buffers */
unsigned long SDL_MintAudio_audiosize;		/* Length of audio buffer=spec->size */
volatile unsigned short SDL_MintAudio_numbuf;		/* Buffer to play */
volatile unsigned short SDL_MintAudio_mutex;
volatile unsigned long SDL_MintAudio_clocktics;
cookie_stfa_t	*SDL_MintAudio_stfa;
unsigned short SDL_MintAudio_hasfpu;

/* MiNT thread variables */
SDL_bool SDL_MintAudio_mint_present;
SDL_bool SDL_MintAudio_quit_thread;
SDL_bool SDL_MintAudio_thread_finished;
long SDL_MintAudio_thread_pid;

/* The callback function, called by each driver whenever needed */

void SDL_MintAudio_Callback(void)
{
	Uint8 *buffer;
	SDL_AudioDevice *audio = SDL_MintAudio_device;

 	buffer = SDL_MintAudio_audiobuf[SDL_MintAudio_numbuf];
	SDL_memset(buffer, audio->spec.silence, audio->spec.size);

	if (audio->paused)
		return;

	if (audio->convert.needed) {
		int silence;

		if ( audio->convert.src_format == AUDIO_U8 ) {
			silence = 0x80;
		} else {
			silence = 0;
		}
		SDL_memset(audio->convert.buf, silence, audio->convert.len);
		audio->spec.callback(audio->spec.userdata,
			(Uint8 *)audio->convert.buf,audio->convert.len);
		SDL_ConvertAudio(&audio->convert);
		SDL_memcpy(buffer, audio->convert.buf, audio->convert.len_cvt);
	} else {
		audio->spec.callback(audio->spec.userdata, buffer, audio->spec.size);
	}
}

/* Add a new frequency/clock/predivisor to the current list */
void SDL_MintAudio_AddFrequency(_THIS, Uint32 frequency, Uint32 clock,
	Uint32 prediv, int gpio_bits)
{
	int i, p;

	if (MINTAUDIO_freqcount==MINTAUDIO_maxfreqs) {
		return;
	}

	/* Search where to insert the frequency (highest first) */
	for (p=0; p<MINTAUDIO_freqcount; p++) {
		if (frequency > MINTAUDIO_frequencies[p].frequency) {
			break;
		}
	}

	/* Put all following ones farer */
	if (MINTAUDIO_freqcount>0) {
		for (i=MINTAUDIO_freqcount; i>p; i--) {
			SDL_memcpy(&MINTAUDIO_frequencies[i], &MINTAUDIO_frequencies[i-1], sizeof(mint_frequency_t));
		}
	}

	/* And insert new one */
	MINTAUDIO_frequencies[p].frequency = frequency;
	MINTAUDIO_frequencies[p].masterclock = clock;
	MINTAUDIO_frequencies[p].predivisor = prediv;
	MINTAUDIO_frequencies[p].gpio_bits = gpio_bits;

	MINTAUDIO_freqcount++;
}

/* Search for the nearest frequency */
int SDL_MintAudio_SearchFrequency(_THIS, int desired_freq)
{
	int i;

	/* Only 1 freq ? */
	if (MINTAUDIO_freqcount==1) {
		return 0;
	}

	/* Check the array */
	for (i=0; i<MINTAUDIO_freqcount; i++) {
		if (desired_freq >= ((MINTAUDIO_frequencies[i].frequency+
			MINTAUDIO_frequencies[i+1].frequency)>>1)) {
			return i;
		}
	}

	/* Not in the array, give the latest */
	return MINTAUDIO_freqcount-1;
}

/* Check if FPU is present */
void SDL_MintAudio_CheckFpu(void)
{
	unsigned long cookie_fpu;

	SDL_MintAudio_hasfpu = 0;
	if (Getcookie(C__FPU, &cookie_fpu) != C_FOUND) {
		return;
	}
	switch ((cookie_fpu>>16)&0xfffe) {
		case 2:
		case 4:
		case 6:
		case 8:
		case 16:
			SDL_MintAudio_hasfpu = 1;
			break;
	}
}

/* The thread function, used under MiNT with xbios */
int SDL_MintAudio_Thread(long param)
{
	SndBufPtr	pointers;
	SDL_bool	buffers_filled[2] = {SDL_FALSE, SDL_FALSE};

	SDL_MintAudio_thread_finished = SDL_FALSE;
	while (!SDL_MintAudio_quit_thread) {
		if (Buffptr(&pointers)!=0)
			continue;

		if (( (unsigned long)pointers.play>=(unsigned long)SDL_MintAudio_audiobuf[0])
			&& ( (unsigned long)pointers.play<=(unsigned long)SDL_MintAudio_audiobuf[1])) 
		{
			/* DMA is reading buffer #0, setup buffer #1 if not already done */
			if (!buffers_filled[1]) {
				SDL_MintAudio_numbuf = 1;
				SDL_MintAudio_Callback();
				Setbuffer(0, SDL_MintAudio_audiobuf[1], SDL_MintAudio_audiobuf[1] + SDL_MintAudio_audiosize);
				buffers_filled[1]=SDL_TRUE;
				buffers_filled[0]=SDL_FALSE;
			}
		} else {
			/* DMA is reading buffer #1, setup buffer #0 if not already done */
			if (!buffers_filled[0]) {
				SDL_MintAudio_numbuf = 0;
				SDL_MintAudio_Callback();
				Setbuffer(0, SDL_MintAudio_audiobuf[0], SDL_MintAudio_audiobuf[0] + SDL_MintAudio_audiosize);
				buffers_filled[0]=SDL_TRUE;
				buffers_filled[1]=SDL_FALSE;
			}
		}

		usleep(100);
	}
	SDL_MintAudio_thread_finished = SDL_TRUE;
	return 0;
}

void SDL_MintAudio_WaitThread(void)
{
	if (!SDL_MintAudio_mint_present)
		return;

	if (SDL_MintAudio_thread_finished)
		return;

	SDL_MintAudio_quit_thread = SDL_TRUE;
	while (!SDL_MintAudio_thread_finished) {
		Syield();
	}
}