raze/libraries/game-music-emu/gme/Vgm_Emu_Impl.cpp

// Game_Music_Emu https://bitbucket.org/mpyne/game-music-emu/

#include "Vgm_Emu.h"

#include <math.h>
#include <string.h>
#include "blargg_endian.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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */

#include "blargg_source.h"

enum {
	cmd_gg_stereo       = 0x4F,
	cmd_psg             = 0x50,
	cmd_ym2413          = 0x51,
	cmd_ym2612_port0    = 0x52,
	cmd_ym2612_port1    = 0x53,
	cmd_ym2151          = 0x54,
	cmd_delay           = 0x61,
	cmd_delay_735       = 0x62,
	cmd_delay_882       = 0x63,
	cmd_byte_delay      = 0x64,
	cmd_end             = 0x66,
	cmd_data_block      = 0x67,
	cmd_short_delay     = 0x70,
	cmd_pcm_delay       = 0x80,
	cmd_pcm_seek        = 0xE0,
	
	pcm_block_type      = 0x00,
	ym2612_dac_port     = 0x2A
};

inline int command_len( int command )
{
	switch ( command >> 4 )
	{
		case 0x03:
		case 0x04:
			return 2;
		
		case 0x05:
		case 0x0A:
		case 0x0B:
			return 3;
		
		case 0x0C:
		case 0x0D:
			return 4;
		
		case 0x0E:
		case 0x0F:
			return 5;
	}
	
	check( false );
	return 1;
}

template<class Emu>
inline void Ym_Emu<Emu>::begin_frame( short* p )
{
	require( enabled() );
	out = p;
	last_time = 0;
}

template<class Emu>
inline int Ym_Emu<Emu>::run_until( int time )
{
	int count = time - last_time;
	if ( count > 0 )
	{
		if ( last_time < 0 )
			return false;
		last_time = time;
		short* p = out;
		out += count * Emu::out_chan_count;
		Emu::run( count, p );
	}
	return true;
}
	
inline Vgm_Emu_Impl::fm_time_t Vgm_Emu_Impl::to_fm_time( vgm_time_t t ) const
{
	return (t * fm_time_factor + fm_time_offset) >> fm_time_bits;
}

inline blip_time_t Vgm_Emu_Impl::to_blip_time( vgm_time_t t ) const
{
	return (t * blip_time_factor) >> blip_time_bits;
}

void Vgm_Emu_Impl::write_pcm( vgm_time_t vgm_time, int amp )
{
	blip_time_t blip_time = to_blip_time( vgm_time );
	int old = dac_amp;
	int delta = amp - old;
	dac_amp = amp;
	if ( old >= 0 )
		dac_synth.offset_inline( blip_time, delta, &blip_buf );
	else
		dac_amp |= dac_disabled;
}

blip_time_t Vgm_Emu_Impl::run_commands( vgm_time_t end_time )
{
	vgm_time_t vgm_time = this->vgm_time; 
	byte const* pos = this->pos;
	if ( pos >= data_end )
	{
		set_track_ended();
		if ( pos > data_end )
			set_warning( "Stream lacked end event" );
	}
	
	while ( vgm_time < end_time && pos < data_end )
	{
		// TODO: be sure there are enough bytes left in stream for particular command
		// so we don't read past end
		switch ( *pos++ )
		{
		case cmd_end:
			pos = loop_begin; // if not looped, loop_begin == data_end
			break;
		
		case cmd_delay_735:
			vgm_time += 735;
			break;
		
		case cmd_delay_882:
			vgm_time += 882;
			break;
		
		case cmd_gg_stereo:
			psg.write_ggstereo( to_blip_time( vgm_time ), *pos++ );
			break;
		
		case cmd_psg:
			psg.write_data( to_blip_time( vgm_time ), *pos++ );
			break;
		
		case cmd_delay:
			vgm_time += pos [1] * 0x100L + pos [0];
			pos += 2;
			break;
		
		case cmd_byte_delay:
			vgm_time += *pos++;
			break;
		
		case cmd_ym2413:
			if ( ym2413.run_until( to_fm_time( vgm_time ) ) )
				ym2413.write( pos [0], pos [1] );
			pos += 2;
			break;
		
		case cmd_ym2612_port0:
			if ( pos [0] == ym2612_dac_port )
			{
				write_pcm( vgm_time, pos [1] );
			}
			else if ( ym2612.run_until( to_fm_time( vgm_time ) ) )
			{
				if ( pos [0] == 0x2B )
				{
					dac_disabled = (pos [1] >> 7 & 1) - 1;
					dac_amp |= dac_disabled;
				}
				ym2612.write0( pos [0], pos [1] );
			}
			pos += 2;
			break;
		
		case cmd_ym2612_port1:
			if ( ym2612.run_until( to_fm_time( vgm_time ) ) )
				ym2612.write1( pos [0], pos [1] );
			pos += 2;
			break;
			
		case cmd_data_block: {
			check( *pos == cmd_end );
			int type = pos [1];
			long size = get_le32( pos + 2 );
			pos += 6;
			if ( type == pcm_block_type )
				pcm_data = pos;
			pos += size;
			break;
		}
		
		case cmd_pcm_seek:
			pcm_pos = pcm_data + pos [3] * 0x1000000L + pos [2] * 0x10000L +
					pos [1] * 0x100L + pos [0];
			pos += 4;
			break;
		
		default:
			int cmd = pos [-1];
			switch ( cmd & 0xF0 )
			{
				case cmd_pcm_delay:
					write_pcm( vgm_time, *pcm_pos++ );
					vgm_time += cmd & 0x0F;
					break;
				
				case cmd_short_delay:
					vgm_time += (cmd & 0x0F) + 1;
					break;
				
				case 0x50:
					pos += 2;
					break;
				
				default:
					pos += command_len( cmd ) - 1;
					set_warning( "Unknown stream event" );
			}
		}
	}
	vgm_time -= end_time;
	this->pos = pos;
	this->vgm_time = vgm_time;
	
	return to_blip_time( end_time );
}

int Vgm_Emu_Impl::play_frame( blip_time_t blip_time, int sample_count, sample_t* buf )
{
	// to do: timing is working mostly by luck
	
	int min_pairs = sample_count >> 1;
	int vgm_time = ((long) min_pairs << fm_time_bits) / fm_time_factor - 1;
	assert( to_fm_time( vgm_time ) <= min_pairs );
	int pairs = min_pairs;
	while ( (pairs = to_fm_time( vgm_time )) < min_pairs )
		vgm_time++;
	//debug_printf( "pairs: %d, min_pairs: %d\n", pairs, min_pairs );
	
	if ( ym2612.enabled() )
	{
		ym2612.begin_frame( buf );
		memset( buf, 0, pairs * stereo * sizeof *buf );
	}
	else if ( ym2413.enabled() )
	{
		ym2413.begin_frame( buf );
	}
	
	run_commands( vgm_time );
	ym2612.run_until( pairs );
	ym2413.run_until( pairs );
	
	fm_time_offset = (vgm_time * fm_time_factor + fm_time_offset) -
			((long) pairs << fm_time_bits);
	
	psg.end_frame( blip_time );
	
	return pairs * stereo;
}

// Update pre-1.10 header FM rates by scanning commands
void Vgm_Emu_Impl::update_fm_rates( long* ym2413_rate, long* ym2612_rate ) const
{
	byte const* p = data + 0x40;
	while ( p < data_end )
	{
		switch ( *p )
		{
		case cmd_end:
			return;
		
		case cmd_psg:
		case cmd_byte_delay:
			p += 2;
			break;
		
		case cmd_delay:
			p += 3;
			break;
		
		case cmd_data_block:
			p += 7 + get_le32( p + 3 );
			break;
		
		case cmd_ym2413:
			*ym2612_rate = 0;
			return;
		
		case cmd_ym2612_port0:
		case cmd_ym2612_port1:
			*ym2612_rate = *ym2413_rate;
			*ym2413_rate = 0;
			return;
		
		case cmd_ym2151:
			*ym2413_rate = 0;
			*ym2612_rate = 0;
			return;
		
		default:
			p += command_len( *p );
		}
	}
}