gmedecoder/gme/Nes_Apu.h

// NES 2A03 APU sound chip emulator

// Nes_Snd_Emu $vers
#ifndef NES_APU_H
#define NES_APU_H

#include "blargg_common.h"
#include "Nes_Oscs.h"

struct apu_state_t;
class Nes_Buffer;

class Nes_Apu {
public:
// Basics

	typedef int nes_time_t; // NES CPU clock cycle count

	// Sets memory reader callback used by DMC oscillator to fetch samples.
	// When callback is invoked, 'user_data' is passed unchanged as the
	// first parameter.
	//void dmc_reader( int (*callback)( void* user_data, int addr ), void* user_data = NULL );

	// Sets buffer to generate sound into, or 0 to mute output (reduces
	// emulation accuracy).
	void set_output( Blip_Buffer* );

	// All time values are the number of CPU clock cycles relative to the
	// beginning of the current time frame. Before resetting the CPU clock
	// count, call end_frame( last_cpu_time ).

	// Writes to register (0x4000-0x4013, and 0x4015 and 0x4017)
	enum { io_addr = 0x4000 };
	enum { io_size = 0x18 };
	void write_register( nes_time_t, int addr, int data );

	// Reads from status register (0x4015)
	enum { status_addr = 0x4015 };
	int read_status( nes_time_t );

	// Runs all oscillators up to specified time, ends current time frame, then
	// starts a new time frame at time 0. Time frames have no effect on emulation
	// and each can be whatever length is convenient.
	void end_frame( nes_time_t );

// Optional

	// Resets internal frame counter, registers, and all oscillators.
	// Uses PAL timing if pal_timing is true, otherwise use NTSC timing.
	// Sets the DMC oscillator's initial DAC value to initial_dmc_dac without
	// any audible click.
	void reset( bool pal_mode = false, int initial_dmc_dac = 0 );

	// Same as set_output(), but for a particular channel
	// 0: Square 1, 1: Square 2, 2: Triangle, 3: Noise, 4: DMC
	enum { osc_count = 5 };
	void set_output( int chan, Blip_Buffer* buf );

	// Adjusts frame period
	void set_tempo( double );

	// Saves/loads exact emulation state
	void save_state( apu_state_t* out ) const;
	void load_state( apu_state_t const& );

	// Sets overall volume (default is 1.0)
	void volume( double );

	// Sets treble equalization (see notes.txt)
	void treble_eq( const blip_eq_t& );

	// Sets IRQ time callback that is invoked when the time of earliest IRQ
	// may have changed, or NULL to disable. When callback is invoked,
	// 'user_data' is passed unchanged as the first parameter.
	//void irq_notifier( void (*callback)( void* user_data ), void* user_data = NULL );

	// Gets time that APU-generated IRQ will occur if no further register reads
	// or writes occur. If IRQ is already pending, returns irq_waiting. If no
	// IRQ will occur, returns no_irq.
	enum { no_irq = INT_MAX/2 + 1 };
	enum { irq_waiting = 0 };
	nes_time_t earliest_irq( nes_time_t ) const;

	// Counts number of DMC reads that would occur if 'run_until( t )' were executed.
	// If last_read is not NULL, set *last_read to the earliest time that
	// 'count_dmc_reads( time )' would result in the same result.
	int count_dmc_reads( nes_time_t t, nes_time_t* last_read = NULL ) const;

	// Time when next DMC memory read will occur
	nes_time_t next_dmc_read_time() const;

	// Runs DMC until specified time, so that any DMC memory reads can be
	// accounted for (i.e. inserting CPU wait states).
	void run_until( nes_time_t );


// Implementation
public:
	Nes_Apu();
	BLARGG_DISABLE_NOTHROW
	// Use set_output() in place of these
	BLARGG_DEPRECATED( void output    (        Blip_Buffer* c ); )
	BLARGG_DEPRECATED( void osc_output( int i, Blip_Buffer* c ); )

	BLARGG_DEPRECATED_TEXT( enum { start_addr = 0x4000 }; )
	BLARGG_DEPRECATED_TEXT( enum { end_addr   = 0x4017 }; )

	blargg_callback<int (*)( void* user_data, int addr )> dmc_reader;
	blargg_callback<void (*)( void* user_data )> irq_notifier;

	void enable_nonlinear_( double sq, double tnd );
	static float tnd_total_() { return 196.015f; }

	void enable_w4011_( bool enable = true ) { enable_w4011 = enable; }

private:
	friend struct Nes_Dmc;

	// noncopyable
	Nes_Apu( const Nes_Apu& );
	Nes_Apu& operator = ( const Nes_Apu& );

	Nes_Osc*            oscs [osc_count];
	Nes_Square          square1;
	Nes_Square          square2;
	Nes_Noise           noise;
	Nes_Triangle        triangle;
	Nes_Dmc             dmc;

	double tempo_;
	nes_time_t last_time; // has been run until this time in current frame
	nes_time_t last_dmc_time;
	nes_time_t earliest_irq_;
	nes_time_t next_irq;
	int frame_period;
	int frame_delay; // cycles until frame counter runs next
	int frame; // current frame (0-3)
	int osc_enables;
	int frame_mode;
	bool irq_flag;
	bool enable_w4011;
	Nes_Square::Synth square_synth; // shared by squares

	void irq_changed();
	void state_restored();
	void run_until_( nes_time_t );

	// TODO: remove
	friend class Nes_Core;
};

inline void Nes_Apu::set_output( int osc, Blip_Buffer* buf )
{
	assert( (unsigned) osc < osc_count );
	oscs [osc]->output = buf;
}

inline Nes_Apu::nes_time_t Nes_Apu::earliest_irq( nes_time_t ) const
{
	return earliest_irq_;
}

inline int Nes_Apu::count_dmc_reads( nes_time_t time, nes_time_t* last_read ) const
{
	return dmc.count_reads( time, last_read );
}

inline Nes_Apu::nes_time_t Nes_Dmc::next_read_time() const
{
	if ( length_counter == 0 )
		return Nes_Apu::no_irq; // not reading

	return apu->last_dmc_time + delay + (bits_remain - 1) * period;
}

inline Nes_Apu::nes_time_t Nes_Apu::next_dmc_read_time() const { return dmc.next_read_time(); }

BLARGG_DEPRECATED( typedef int      nes_time_t; ) // use your own typedef
BLARGG_DEPRECATED( typedef unsigned nes_addr_t; ) // use your own typedef

BLARGG_DEPRECATED_TEXT( inline void Nes_Apu::output    (        Blip_Buffer* c ) { set_output( c    ); } )
BLARGG_DEPRECATED_TEXT( inline void Nes_Apu::osc_output( int i, Blip_Buffer* c ) { set_output( i, c ); } )

#endif