Sap_Apu.h

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// Atari POKEY sound chip emulator
 
// Game_Music_Emu https://bitbucket.org/mpyne/game-music-emu/
#ifndef SAP_APU_H
#define SAP_APU_H
 
#include "blargg_common.h"
#include "Blip_Buffer.h"
 
class Sap_Apu_Impl;
 
class Sap_Apu {
public:
        enum { osc_count = 4 };
        void osc_output( int index, Blip_Buffer* );
        
        void reset( Sap_Apu_Impl* );
        
        enum { start_addr = 0xD200 };
        enum { end_addr   = 0xD209 };
        void write_data( blip_time_t, unsigned addr, int data );
        
        void end_frame( blip_time_t );
        
public:
        Sap_Apu();
private:
        struct osc_t
        {
                unsigned char regs [2];
                unsigned char phase;
                unsigned char invert;
                int last_amp;
                blip_time_t delay;
                blip_time_t period; // always recalculated before use; here for convenience
                Blip_Buffer* output;
        };
        osc_t oscs [osc_count];
        Sap_Apu_Impl* impl;
        blip_time_t last_time;
        int poly5_pos;
        int poly4_pos;
        int polym_pos;
        int control;
        
        void calc_periods();
        void run_until( blip_time_t );
        
        enum { poly4_len  = (1L <<  4) - 1 };
        enum { poly9_len  = (1L <<  9) - 1 };
        enum { poly17_len = (1L << 17) - 1 };
        friend class Sap_Apu_Impl;
};
 
// Common tables and Blip_Synth that can be shared among multiple Sap_Apu objects
class Sap_Apu_Impl {
public:
        Blip_Synth<blip_good_quality,1> synth;
        
        Sap_Apu_Impl();
        void volume( double d ) { synth.volume( 1.0 / Sap_Apu::osc_count / 30 * d ); }
        
private:
        typedef unsigned char byte;
        byte poly4  [Sap_Apu::poly4_len  / 8 + 1];
        byte poly9  [Sap_Apu::poly9_len  / 8 + 1];
        byte poly17 [Sap_Apu::poly17_len / 8 + 1];
        friend class Sap_Apu;
};
 
inline void Sap_Apu::osc_output( int i, Blip_Buffer* b )
{
        assert( (unsigned) i < osc_count );
        oscs [i].output = b;
}
 
#endif