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336 lines
6.7 KiB
C++
336 lines
6.7 KiB
C++
// Gb_Snd_Emu 0.1.5. http://www.slack.net/~ant/
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#include "Gb_Apu.h"
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#include <string.h>
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/* Copyright (C) 2003-2006 Shay Green. This module is free software; you
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can redistribute it and/or modify it under the terms of the GNU Lesser
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General Public License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version. This
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module is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
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details. You should have received a copy of the GNU Lesser General Public
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License along with this module; if not, write to the Free Software Foundation,
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Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */
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#include "blargg_source.h"
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// Gb_Osc
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void Gb_Osc::reset()
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{
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delay = 0;
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last_amp = 0;
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length = 0;
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output_select = 3;
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output = outputs [output_select];
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}
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void Gb_Osc::clock_length()
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{
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if ( (regs [4] & len_enabled_mask) && length )
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length--;
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}
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// Gb_Env
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void Gb_Env::clock_envelope()
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{
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if ( env_delay && !--env_delay )
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{
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env_delay = regs [2] & 7;
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int v = volume - 1 + (regs [2] >> 2 & 2);
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if ( (unsigned) v < 15 )
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volume = v;
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}
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}
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bool Gb_Env::write_register( int reg, int data )
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{
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switch ( reg )
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{
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case 1:
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length = 64 - (regs [1] & 0x3F);
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break;
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case 2:
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if ( !(data >> 4) )
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enabled = false;
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break;
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case 4:
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if ( data & trigger )
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{
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env_delay = regs [2] & 7;
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volume = regs [2] >> 4;
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enabled = true;
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if ( length == 0 )
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length = 64;
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return true;
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}
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}
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return false;
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}
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// Gb_Square
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void Gb_Square::reset()
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{
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phase = 0;
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sweep_freq = 0;
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sweep_delay = 0;
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Gb_Env::reset();
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}
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void Gb_Square::clock_sweep()
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{
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int sweep_period = (regs [0] & period_mask) >> 4;
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if ( sweep_period && sweep_delay && !--sweep_delay )
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{
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sweep_delay = sweep_period;
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regs [3] = sweep_freq & 0xFF;
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regs [4] = (regs [4] & ~0x07) | (sweep_freq >> 8 & 0x07);
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int offset = sweep_freq >> (regs [0] & shift_mask);
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if ( regs [0] & 0x08 )
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offset = -offset;
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sweep_freq += offset;
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if ( sweep_freq < 0 )
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{
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sweep_freq = 0;
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}
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else if ( sweep_freq >= 2048 )
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{
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sweep_delay = 0; // don't modify channel frequency any further
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sweep_freq = 2048; // silence sound immediately
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}
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}
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}
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void Gb_Square::run( blip_time_t time, blip_time_t end_time, int playing )
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{
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if ( sweep_freq == 2048 )
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playing = false;
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static unsigned char const table [4] = { 1, 2, 4, 6 };
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int const duty = table [regs [1] >> 6];
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int amp = volume & playing;
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if ( phase >= duty )
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amp = -amp;
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int frequency = this->frequency();
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if ( unsigned (frequency - 1) > 2040 ) // frequency < 1 || frequency > 2041
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{
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// really high frequency results in DC at half volume
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amp = volume >> 1;
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playing = false;
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}
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{
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int delta = amp - last_amp;
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if ( delta )
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{
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last_amp = amp;
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synth->offset( time, delta, output );
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}
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}
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time += delay;
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if ( !playing )
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time = end_time;
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if ( time < end_time )
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{
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int const period = (2048 - frequency) * 4;
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Blip_Buffer* const output = this->output;
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int phase = this->phase;
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int delta = amp * 2;
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do
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{
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phase = (phase + 1) & 7;
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if ( phase == 0 || phase == duty )
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{
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delta = -delta;
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synth->offset_inline( time, delta, output );
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}
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time += period;
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}
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while ( time < end_time );
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this->phase = phase;
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last_amp = delta >> 1;
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}
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delay = time - end_time;
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}
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// Gb_Noise
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void Gb_Noise::run( blip_time_t time, blip_time_t end_time, int playing )
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{
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int amp = volume & playing;
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int tap = 13 - (regs [3] & 8);
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if ( bits >> tap & 2 )
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amp = -amp;
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{
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int delta = amp - last_amp;
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if ( delta )
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{
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last_amp = amp;
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synth->offset( time, delta, output );
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}
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}
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time += delay;
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if ( !playing )
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time = end_time;
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if ( time < end_time )
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{
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static unsigned char const table [8] = { 8, 16, 32, 48, 64, 80, 96, 112 };
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int period = table [regs [3] & 7] << (regs [3] >> 4);
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// keep parallel resampled time to eliminate time conversion in the loop
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Blip_Buffer* const output = this->output;
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const blip_resampled_time_t resampled_period =
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output->resampled_duration( period );
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blip_resampled_time_t resampled_time = output->resampled_time( time );
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unsigned bits = this->bits;
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int delta = amp * 2;
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do
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{
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unsigned changed = (bits >> tap) + 1;
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time += period;
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bits <<= 1;
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if ( changed & 2 )
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{
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delta = -delta;
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bits |= 1;
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synth->offset_resampled( resampled_time, delta, output );
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}
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resampled_time += resampled_period;
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}
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while ( time < end_time );
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this->bits = bits;
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last_amp = delta >> 1;
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}
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delay = time - end_time;
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}
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// Gb_Wave
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inline void Gb_Wave::write_register( int reg, int data )
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{
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switch ( reg )
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{
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case 0:
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if ( !(data & 0x80) )
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enabled = false;
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break;
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case 1:
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length = 256 - regs [1];
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break;
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case 2:
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volume = data >> 5 & 3;
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break;
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case 4:
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if ( data & trigger & regs [0] )
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{
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wave_pos = 0;
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enabled = true;
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if ( length == 0 )
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length = 256;
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}
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}
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}
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void Gb_Wave::run( blip_time_t time, blip_time_t end_time, int playing )
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{
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int volume_shift = (volume - 1) & 7; // volume = 0 causes shift = 7
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int frequency;
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{
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int amp = (wave [wave_pos] >> volume_shift & playing) * 2;
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frequency = this->frequency();
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if ( unsigned (frequency - 1) > 2044 ) // frequency < 1 || frequency > 2045
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{
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amp = 30 >> volume_shift & playing;
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playing = false;
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}
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int delta = amp - last_amp;
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if ( delta )
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{
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last_amp = amp;
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synth->offset( time, delta, output );
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}
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}
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time += delay;
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if ( !playing )
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time = end_time;
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if ( time < end_time )
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{
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Blip_Buffer* const output = this->output;
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int const period = (2048 - frequency) * 2;
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int wave_pos = (this->wave_pos + 1) & (wave_size - 1);
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do
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{
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int amp = (wave [wave_pos] >> volume_shift) * 2;
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wave_pos = (wave_pos + 1) & (wave_size - 1);
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int delta = amp - last_amp;
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if ( delta )
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{
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last_amp = amp;
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synth->offset_inline( time, delta, output );
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}
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time += period;
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}
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while ( time < end_time );
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this->wave_pos = (wave_pos - 1) & (wave_size - 1);
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}
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delay = time - end_time;
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}
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// Gb_Apu::write_osc
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void Gb_Apu::write_osc( int index, int reg, int data )
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{
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reg -= index * 5;
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Gb_Square* sq = &square2;
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switch ( index )
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{
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case 0:
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sq = &square1;
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case 1:
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if ( sq->write_register( reg, data ) && index == 0 )
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{
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square1.sweep_freq = square1.frequency();
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if ( (regs [0] & sq->period_mask) && (regs [0] & sq->shift_mask) )
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{
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square1.sweep_delay = 1; // cause sweep to recalculate now
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square1.clock_sweep();
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}
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}
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break;
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case 2:
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wave.write_register( reg, data );
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break;
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case 3:
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if ( noise.write_register( reg, data ) )
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noise.bits = 0x7FFF;
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}
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}
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