ymz280b.c

十七种模拟器源代码 非常有用的作课程设计不可缺少的

		UINT32 new_samples, samples_left;
		UINT32 final_pos;
		int remaining = length;
		int lvol = voice->output_left;
		int rvol = voice->output_right;

		/* quick out if we're not playing and we're at 0 */
		if (!voice->playing && curr == 0)
			continue;

		/* finish off the current sample */
		if (voice->output_pos > 0)
		{
			/* interpolate */
			while (remaining > 0 && voice->output_pos < FRAC_ONE)
			{
				int interp_sample = (((INT32)prev * (FRAC_ONE - voice->output_pos)) + ((INT32)curr * voice->output_pos)) >> FRAC_BITS;
				*ldest++ += interp_sample * lvol;
				*rdest++ += interp_sample * rvol;
				voice->output_pos += voice->output_step;
				remaining--;
			}

			/* if we're over, continue; otherwise, we're done */
			if (voice->output_pos >= FRAC_ONE)
				voice->output_pos -= FRAC_ONE;
			else
				continue;
		}

		/* compute how many new samples we need */
		final_pos = voice->output_pos + remaining * voice->output_step;
		new_samples = (final_pos + FRAC_ONE - 1) >> FRAC_BITS;
		if (new_samples > MAX_SAMPLE_CHUNK)
			new_samples = MAX_SAMPLE_CHUNK;
		samples_left = new_samples;

		/* generate them into our buffer */
		if (voice->playing)
		{
			switch (voice->mode)
			{
				case 1:	samples_left = generate_adpcm(voice, chip->region_base, scratch, new_samples);	break;
				case 2:	samples_left = generate_pcm8(voice, chip->region_base, scratch, new_samples);	break;
				case 3:	samples_left = generate_pcm16(voice, chip->region_base, scratch, new_samples);	break;
				default:
				case 0:	samples_left = 0; memset(scratch, 0, new_samples * sizeof(scratch[0]));			break;
			}
		}

		/* if there are leftovers, ramp back to 0 */
		if (samples_left)
		{
			int base = new_samples - samples_left;
			int i, t = (base == 0) ? curr : scratch[base - 1];
			for (i = 0; (UINT32)i < samples_left; i++)
			{
				if (t < 0) t = -((-t * 15) >> 4);
				else if (t > 0) t = (t * 15) >> 4;
				scratch[base + i] = t;
			}

			/* if we hit the end and IRQs are enabled, signal it */
			if (base != 0)
			{
				voice->playing = 0;
				chip->status_register |= 1 << v;
				update_irq_state(chip);
			}
		}

		/* advance forward one sample */
		prev = curr;
		curr = *curr_data++;

		/* then sample-rate convert with linear interpolation */
		while (remaining > 0)
		{
			/* interpolate */
			while (remaining > 0 && voice->output_pos < FRAC_ONE)
			{
				int interp_sample = (((INT32)prev * (FRAC_ONE - voice->output_pos)) + ((INT32)curr * voice->output_pos)) >> FRAC_BITS;
				*ldest++ += interp_sample * lvol;
				*rdest++ += interp_sample * rvol;
				voice->output_pos += voice->output_step;
				remaining--;
			}

			/* if we're over, grab the next samples */
			if (voice->output_pos >= FRAC_ONE)
			{
				voice->output_pos -= FRAC_ONE;
				prev = curr;
				curr = *curr_data++;
			}
		}

		/* remember the last samples */
		voice->last_sample = prev;
		voice->curr_sample = curr;
	}

	/* mix and clip the result */
	for (v = 0; v < length; v++)
	{
		int lsamp = lacc[v] / 256;
		int rsamp = racc[v] / 256;

		if (lsamp < -32768) lsamp = -32768;
		else if (lsamp > 32767) lsamp = 32767;
		if (rsamp < -32768) rsamp = -32768;
		else if (rsamp > 32767) rsamp = 32767;

		buffer[0][v] = lsamp;
		buffer[1][v] = rsamp;
	}
}


void Addymz280b_savedata() {
  AddSaveData(SAVE_USER_0,(UINT8*)&ymz280b[0].voice,sizeof(struct YMZ280BVoice)*8);
  AddSaveData(SAVE_USER_1,(UINT8*)&ymz280b[1].voice,sizeof(struct YMZ280BVoice)*8);
}


/**********************************************************************************************

     YMZ280B_sh_start -- start emulation of the YMZ280B

***********************************************************************************************/

int YMZ280B_sh_start(const struct YMZ280Binterface *intf)
{
	char stream_name[2][40];
	const char *stream_name_ptrs[2];
	int vol[2];
	int i;

	/* compute ADPCM tables */
	compute_tables();

	/* initialize the voices */
	memset(&ymz280b, 0, sizeof(ymz280b));
	for (i = 0; i < intf->num; i++)
	{
		/* generate the name and create the stream */
		sprintf(stream_name[0], "%s #%d Ch1", "YMZ280B", i);
		sprintf(stream_name[1], "%s #%d Ch2", "YMZ280B", i);
		stream_name_ptrs[0] = stream_name[0];
		stream_name_ptrs[1] = stream_name[1];

		/* set the volumes */
		vol[0] = intf->mixing_level[i] & 0xffff;
		vol[1] = intf->mixing_level[i] >> 16;

		/* create the stream */
		ymz280b[i].stream = stream_init_multim(2, stream_name_ptrs, vol, audio_sample_rate, i, ymz280b_update);
		if (ymz280b[i].stream == -1)
			return 1;

		/* initialize the rest of the structure */
		ymz280b[i].master_clock = (double)intf->baseclock[i] / 384.0;
		ymz280b[i].region_base = load_region[intf->region[i]];
		ymz280b[i].irq_callback = intf->irq_callback[i];
	}

	/* allocate memory */
	accumulator = malloc(sizeof(accumulator[0]) * 2 * MAX_SAMPLE_CHUNK);
	scratch = malloc(sizeof(scratch[0]) * MAX_SAMPLE_CHUNK);
	if (!accumulator || !scratch)
		return 1;

	Addymz280b_savedata();
	/* success */
	return 0;
}



/**********************************************************************************************

     YMZ280B_sh_stop -- stop emulation of the YMZ280B

***********************************************************************************************/

void YMZ280B_sh_stop(void)
{
	/* free memory */
	if (accumulator)
		free(accumulator);
	accumulator = NULL;

	if (scratch)
		free(scratch);
	scratch = NULL;
}



/**********************************************************************************************

     write_to_register -- handle a write to the current register

***********************************************************************************************/

static void write_to_register(struct YMZ280BChip *chip, int data)
{
	struct YMZ280BVoice *voice;
	int i;

	/* force an update */
	stream_update(chip->stream, 0);

	/* lower registers follow a pattern */
	if (chip->current_register < 0x80)
	{
		voice = &chip->voice[(chip->current_register >> 2) & 7];

		switch (chip->current_register & 0xe3)
		{
			case 0x00:		/* pitch low 8 bits */
				voice->fnum = (voice->fnum & 0x100) | (data & 0xff);
				update_step(chip, voice);
				break;

			case 0x01:		/* pitch upper 1 bit, loop, key on, mode */
				voice->fnum = (voice->fnum & 0xff) | ((data & 0x01) << 8);
				voice->looping = (data & 0x10) >> 4;
				voice->mode = (data & 0x60) >> 5;
				if (!voice->keyon && (data & 0x80) && chip->keyon_enable)
				{
					voice->playing = 1;
					voice->position = voice->start;
					voice->signal = voice->loop_signal = 0;
					voice->step = voice->loop_step = 0x7f;
					voice->loop_count = 0;
				}
				if (voice->keyon && !(data & 0x80) && !voice->looping){
//ks start
				  voice->playing = 0;
				  chip->status_register &= ~(1 << ((chip->
current_register >> 2) & 7));
				}
//ks end				
				voice->keyon = (data & 0x80) >> 7;
				update_step(chip, voice);
				break;

			case 0x02:		/* total level */
				voice->level = data;
				update_volumes(voice);
				break;

			case 0x03:		/* pan */
				voice->pan = data & 0x0f;
				update_volumes(voice);
				break;

			case 0x20:		/* start address high */
				voice->start = (voice->start & (0x00ffff << 1)) | (data << 17);
				break;

			case 0x21:		/* loop start address high */
				voice->loop_start = (voice->loop_start & (0x00ffff << 1)) | (data << 17);
				break;

			case 0x22:		/* loop end address high */
				voice->loop_end = (voice->loop_end & (0x00ffff << 1)) | (data << 17);
				break;

			case 0x23:		/* stop address high */
				voice->stop = (voice->stop & (0x00ffff << 1)) | (data << 17);
				break;

			case 0x40:		/* start address middle */
				voice->start = (voice->start & (0xff00ff << 1)) | (data << 9);
				break;

			case 0x41:		/* loop start address middle */
				voice->loop_start = (voice->loop_start & (0xff00ff << 1)) | (data << 9);
				break;

			case 0x42:		/* loop end address middle */
				voice->loop_end = (voice->loop_end & (0xff00ff << 1)) | (data << 9);
				break;

			case 0x43:		/* stop address middle */
				voice->stop = (voice->stop & (0xff00ff << 1)) | (data << 9);
				break;

			case 0x60:		/* start address low */
				voice->start = (voice->start & (0xffff00 << 1)) | (data << 1);
				break;

			case 0x61:		/* loop start address low */
				voice->loop_start = (voice->loop_start & (0xffff00 << 1)) | (data << 1);
				break;

			case 0x62:		/* loop end address low */
				voice->loop_end = (voice->loop_end & (0xffff00 << 1)) | (data << 1);
				break;

			case 0x63:		/* stop address low */
				voice->stop = (voice->stop & (0xffff00 << 1)) | (data << 1);
				break;

			default:
#ifdef RAINE_DEBUG
			  print_debug("YMZ280B: unknown register write %02X = %02X\n", chip->current_register, data);
#endif
				break;
		}
	}

	/* upper registers are special */
	else
	{
		switch (chip->current_register)
		{
			case 0xfe:		/* IRQ mask */
				chip->irq_mask = data;
				update_irq_state(chip);
				break;

			case 0xff:		/* IRQ enable, test, etc */
				chip->irq_enable = (data & 0x10) >> 4;
				update_irq_state(chip);
// ks start
				if (chip->keyon_enable && !(data & 0x80))
				  for (i = 0; i < 8; i++)
				    chip->voice[i].playing = 0;
				if (!chip->keyon_enable && (data & 0x80))
				  for (i = 0; i < 8; i++)
				    if (chip->voice[i].keyon && chip
->voice[i].looping)
				      chip->voice[i].playing =
 1;
				chip->keyon_enable = (data & 0x80) >> 7;
// ks end				
				break;

			default:
#ifdef RAINE_DEBUG
			  print_debug("YMZ280B: unknown register write %02X = %02X\n", chip->current_register, data);
#endif			  
				break;
		}
	}
}



/**********************************************************************************************

     compute_status -- determine the status bits

***********************************************************************************************/

static int compute_status(struct YMZ280BChip *chip)
{
	UINT8 result = chip->status_register;

	/* force an update */
	stream_update(chip->stream, 0);

	/* clear the IRQ state */
	chip->status_register = 0;
	update_irq_state(chip);

	return result;
}



/**********************************************************************************************

     YMZ280B_status_0_r/YMZ280B_status_1_r -- handle a read from the status register

***********************************************************************************************/

READ_HANDLER( YMZ280B_status_0_r )
{
	return compute_status(&ymz280b[0]);
}

READ_HANDLER( YMZ280B_status_1_r )
{
	return compute_status(&ymz280b[1]);
}



/**********************************************************************************************

     YMZ280B_register_0_w/YMZ280B_register_1_w -- handle a write to the register select

***********************************************************************************************/

WRITE_HANDLER( YMZ280B_register_0_w )
{
	ymz280b[0].current_register = data;
}

WRITE_HANDLER( YMZ280B_register_1_w )
{
	ymz280b[1].current_register = data;
}



/**********************************************************************************************

     YMZ280B_data_0_w/YMZ280B_data_1_w -- handle a write to the current register

***********************************************************************************************/

WRITE_HANDLER( YMZ280B_data_0_w )
{
	write_to_register(&ymz280b[0], data);
}

WRITE_HANDLER( YMZ280B_data_1_w )
{
	write_to_register(&ymz280b[1], data);
}