quickerNES/source/core/Nes_Namco_Apu.cpp

// Nes_Snd_Emu 0.1.7. http://www.slack.net/~ant/

#include "Nes_Namco_Apu.h"

/* Copyright (C) 2003-2006 Shay Green. This module 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
module 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 module; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */

#include "blargg_source.h"

Nes_Namco_Apu::Nes_Namco_Apu()
{
	output( NULL );
	volume( 1.0 );
	reset();
}

Nes_Namco_Apu::~Nes_Namco_Apu()
{
}

void Nes_Namco_Apu::reset()
{
	last_time = 0;
	addr_reg = 0;

	int i;
	for ( i = 0; i < reg_count; i++ )
		reg [i] = 0;

	for ( i = 0; i < osc_count; i++ )
	{
		Namco_Osc& osc = oscs [i];
		osc.delay = 0;
		osc.last_amp = 0;
		osc.wave_pos = 0;
	}
}

void Nes_Namco_Apu::output( Blip_Buffer* buf )
{
	for ( int i = 0; i < osc_count; i++ )
		osc_output( i, buf );
}

/*
void Nes_Namco_Apu::reflect_state( Tagged_Data& data )
{
	reflect_int16( data, 'ADDR', &addr_reg );

	static const char hex [17] = "0123456789ABCDEF";
	int i;
	for ( i = 0; i < reg_count; i++ )
		reflect_int16( data, 'RG\0\0' + hex [i >> 4] * 0x100 + hex [i & 15], &reg [i] );

	for ( i = 0; i < osc_count; i++ )
	{
		reflect_int32( data, 'DLY0' + i, &oscs [i].delay );
		reflect_int16( data, 'POS0' + i, &oscs [i].wave_pos );
	}
}
*/

void Nes_Namco_Apu::end_frame( nes_time_t time )
{
	if ( time > last_time )
		run_until( time );

	last_time -= time;
}

void Nes_Namco_Apu::run_until( nes_time_t nes_end_time )
{
	int active_oscs = (reg [0x7F] >> 4 & 7) + 1;
	for ( int i = osc_count - active_oscs; i < osc_count; i++ )
	{
		Namco_Osc& osc = oscs [i];
		Blip_Buffer* output = osc.output;
		if ( !output )
			continue;

		blip_resampled_time_t time =
				output->resampled_time( last_time ) + osc.delay;
		blip_resampled_time_t end_time = output->resampled_time( nes_end_time );
		osc.delay = 0;
		if ( time < end_time )
		{
			const uint8_t* osc_reg = &reg [i * 8 + 0x40];
			if ( !(osc_reg [4] & 0xE0) )
				continue;

			int volume = osc_reg [7] & 15;
			if ( !volume )
				continue;

			long freq = (osc_reg [4] & 3) * 0x10000 + osc_reg [2] * 0x100L + osc_reg [0];
			if ( freq < 64 * active_oscs )
				continue; // prevent low frequencies from excessively delaying freq changes
			blip_resampled_time_t period =
					output->resampled_duration( 983040 ) / freq * active_oscs;

			int wave_size = 32 - (osc_reg [4] >> 2 & 7) * 4;
			if ( !wave_size )
				continue;

			int last_amp = osc.last_amp;
			int wave_pos = osc.wave_pos;

			do
			{
				// read wave sample
				int addr = wave_pos + osc_reg [6];
				int sample = reg [addr >> 1] >> (addr << 2 & 4);
				wave_pos++;
				sample = (sample & 15) * volume;

				// output impulse if amplitude changed
				int delta = sample - last_amp;
				if ( delta )
				{
					last_amp = sample;
					synth.offset_resampled( time, delta, output );
				}

				// next sample
				time += period;
				if ( wave_pos >= wave_size )
					wave_pos = 0;
			}
			while ( time < end_time );

			osc.wave_pos = wave_pos;
			osc.last_amp = last_amp;
		}
		osc.delay = time - end_time;
	}

	last_time = nes_end_time;
}

void Nes_Namco_Apu::save_state( namco_state_t* out ) const
{
	out->addr = addr_reg;
	for ( int r = 0; r < reg_count; r++ )
		out->regs [ r ] = reg [ r ];

	for ( int i = 0; i < osc_count; i++ )
	{
		Namco_Osc const& osc = oscs [ i ];

		out->delays [ i ] = osc.delay;
		out->positions [ i ] = osc.wave_pos;
	}
}

void Nes_Namco_Apu::load_state( namco_state_t const& in )
{
	reset();
	addr_reg = in.addr;
	for ( int r = 0; r < reg_count; r++ )
		reg [ r ] = in.regs [ r ];

	for ( int i = 0; i < osc_count; i++ )
	{
		Namco_Osc& osc = oscs [ i ];

		osc.delay = in.delays [ i ];
		osc.wave_pos = in.positions [ i ];
	}

	run_until( last_time );
}