raze-gles/libraries/game-music-emu/gme/Gb_Cpu.h

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2019-11-10 22:58:51 +00:00
// Nintendo Game Boy CPU emulator
// Treats every instruction as taking 4 cycles
// Game_Music_Emu https://bitbucket.org/mpyne/game-music-emu/
#ifndef GB_CPU_H
#define GB_CPU_H
#include "blargg_common.h"
#include "blargg_endian.h"
typedef unsigned gb_addr_t; // 16-bit CPU address
class Gb_Cpu {
enum { clocks_per_instr = 4 };
public:
// Clear registers and map all pages to unmapped
void reset( void* unmapped = 0 );
// Map code memory (memory accessed via the program counter). Start and size
// must be multiple of page_size.
enum { page_size = 0x2000 };
void map_code( gb_addr_t start, unsigned size, void* code );
uint8_t* get_code( gb_addr_t );
// Push a byte on the stack
void push_byte( int );
// Game Boy Z80 registers. *Not* kept updated during a call to run().
struct core_regs_t {
#if BLARGG_BIG_ENDIAN
uint8_t b, c, d, e, h, l, flags, a;
#else
uint8_t c, b, e, d, l, h, a, flags;
#endif
};
struct registers_t : core_regs_t {
long pc; // more than 16 bits to allow overflow detection
uint16_t sp;
};
registers_t r;
// Interrupt enable flag set by EI and cleared by DI
//bool interrupts_enabled; // unused
// Base address for RST vectors (normally 0)
gb_addr_t rst_base;
// If CPU executes opcode 0xFF at this address, it treats as illegal instruction
enum { idle_addr = 0xF00D };
// Run CPU for at least 'count' cycles and return false, or return true if
// illegal instruction is encountered.
bool run( blargg_long count );
// Number of clock cycles remaining for most recent run() call
blargg_long remain() const { return state->remain * clocks_per_instr; }
// Can read this many bytes past end of a page
enum { cpu_padding = 8 };
public:
Gb_Cpu() : rst_base( 0 ) { state = &state_; }
enum { page_shift = 13 };
enum { page_count = 0x10000 >> page_shift };
private:
// noncopyable
Gb_Cpu( const Gb_Cpu& );
Gb_Cpu& operator = ( const Gb_Cpu& );
struct state_t {
uint8_t* code_map [page_count + 1];
blargg_long remain;
};
state_t* state; // points to state_ or a local copy within run()
state_t state_;
void set_code_page( int, uint8_t* );
};
inline uint8_t* Gb_Cpu::get_code( gb_addr_t addr )
{
return state->code_map [addr >> page_shift] + addr
#if !BLARGG_NONPORTABLE
% (unsigned) page_size
#endif
;
}
#endif