Nes_Apu.h

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// NES 2A03 APU sound chip emulator
 
// Nes_Snd_Emu 0.1.8
#ifndef NES_APU_H
#define NES_APU_H
 
#include "blargg_common.h"
 
typedef blargg_long nes_time_t; // CPU clock cycle count
typedef unsigned nes_addr_t; // 16-bit memory address
 
#include "Nes_Oscs.h"
 
struct apu_state_t;
class Nes_Buffer;
 
class Nes_Apu {
public:
        // Set buffer to generate all sound into, or disable sound if NULL
        void output( Blip_Buffer* );
        
        // Set 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, nes_addr_t ), void* user_data = NULL );
        
        // 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 ).
        
        // Write to register (0x4000-0x4017, except 0x4014 and 0x4016)
        enum { start_addr = 0x4000 };
        enum { end_addr   = 0x4017 };
        void write_register( nes_time_t, nes_addr_t, int data );
        
        // Read from status register at 0x4015
        enum { status_addr = 0x4015 };
        int read_status( nes_time_t );
        
        // Run all oscillators up to specified time, end current time frame, then
        // start 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 );
        
// Additional optional features (can be ignored without any problem)
 
        // Reset internal frame counter, registers, and all oscillators.
        // Use PAL timing if pal_timing is true, otherwise use NTSC timing.
        // Set 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 );
        
        // Adjust frame period
        void set_tempo( double );
        
        // Save/load exact emulation state
        void save_state( apu_state_t* out ) const;
        void load_state( apu_state_t const& );
        
        // Set overall volume (default is 1.0)
        void volume( double );
        
        // Set treble equalization (see notes.txt)
        void treble_eq( const blip_eq_t& );
        
        // Set sound output of specific oscillator to buffer. If buffer is NULL,
        // the specified oscillator is muted and emulation accuracy is reduced.
        // The oscillators are indexed as follows: 0) Square 1, 1) Square 2,
        // 2) Triangle, 3) Noise, 4) DMC.
        enum { osc_count = 5 };
        void osc_output( int index, Blip_Buffer* buffer );
        
        // Set 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 );
        
        // Get 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;
        
        // Count 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;
        
        // Run 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 );
        
public:
        Nes_Apu();
        BLARGG_DISABLE_NOTHROW
private:
        friend class Nes_Nonlinearizer;
        void enable_nonlinear( double volume );
        static double nonlinear_tnd_gain() { return 0.75; }
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;
        void (*irq_notifier_)( void* user_data );
        void* irq_data;
        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::osc_output( int osc, Blip_Buffer* buf )
{
        assert( (unsigned) osc < osc_count );
        oscs [osc]->output = buf;
}
 
inline nes_time_t Nes_Apu::earliest_irq( nes_time_t ) const
{
        return earliest_irq_;
}
 
inline void Nes_Apu::dmc_reader( int (*func)( void*, nes_addr_t ), void* user_data )
{
        dmc.prg_reader_data = user_data;
        dmc.prg_reader = func;
}
 
inline void Nes_Apu::irq_notifier( void (*func)( void* user_data ), void* user_data )
{
        irq_notifier_ = func;
        irq_data = user_data;
}
 
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_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 + long (bits_remain - 1) * period;
}
 
inline nes_time_t Nes_Apu::next_dmc_read_time() const { return dmc.next_read_time(); }
 
#endif