Ay_Cpu.h

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// Z80 CPU emulator
 
// Game_Music_Emu https://bitbucket.org/mpyne/game-music-emu/
#ifndef AY_CPU_H
#define AY_CPU_H
 
#include "blargg_endian.h"
 
typedef blargg_long cpu_time_t;
 
// must be defined by caller
void ay_cpu_out( class Ay_Cpu*, cpu_time_t, unsigned addr, int data );
int ay_cpu_in( class Ay_Cpu*, unsigned addr );
 
class Ay_Cpu {
public:
        // Clear all registers and keep pointer to 64K memory passed in
        void reset( void* mem_64k );
        
        // Run until specified time is reached. Returns true if suspicious/unsupported
        // instruction was encountered at any point during run.
        bool run( cpu_time_t end_time );
        
        // Time of beginning of next instruction
        cpu_time_t time() const             { return state->time + state->base; }
        
        // Alter current time. Not supported during run() call.
        void set_time( cpu_time_t t )       { state->time = t - state->base; }
        void adjust_time( int delta )       { state->time += delta; }
        
        #if BLARGG_BIG_ENDIAN
                struct regs_t { uint8_t b, c, d, e, h, l, flags, a; };
        #else
                struct regs_t { uint8_t c, b, e, d, l, h, a, flags; };
        #endif
        BOOST_STATIC_ASSERT( sizeof (regs_t) == 8 );
        
        struct pairs_t { uint16_t bc, de, hl, fa; };
        
        // Registers are not updated until run() returns
        struct registers_t {
                uint16_t pc;
                uint16_t sp;
                uint16_t ix;
                uint16_t iy;
                union {
                        regs_t b; //  b.b, b.c, b.d, b.e, b.h, b.l, b.flags, b.a
                        pairs_t w; // w.bc, w.de, w.hl. w.fa
                };
                union {
                        regs_t b;
                        pairs_t w;
                } alt;
                uint8_t iff1;
                uint8_t iff2;
                uint8_t r;
                uint8_t i;
                uint8_t im;
        };
        //registers_t r; (below for efficiency)
        
        // can read this far past end of memory
        enum { cpu_padding = 0x100 };
        
public:
        Ay_Cpu();
private:
        uint8_t szpc [0x200];
        uint8_t* mem;
        cpu_time_t end_time_;
        struct state_t {
                cpu_time_t base;
                cpu_time_t time;
        };
        state_t* state; // points to state_ or a local copy within run()
        state_t state_;
        void set_end_time( cpu_time_t t );
public:
        registers_t r;
};
 
inline void Ay_Cpu::set_end_time( cpu_time_t t )
{
        cpu_time_t delta = state->base - t;
        state->base = t;
        state->time += delta;
}
 
#endif