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|
use std::fs::File;
use std::io::Read;
#[derive(Debug)]
pub struct Flags {
pub zero: u8, //Zero flag
pub n: u8, //Subtraction flag (BCD)
pub h: u8, //Half carry flag (BCD)
pub carry: u8, //Carry flag
}
impl Flags {
fn new() -> Self {
Flags {
zero: 0,
n: 0,
h: 0,
carry: 0,
}
}
}
#[derive(Debug)]
pub struct Chip {
pub a: u8, //Upper bits of AF, the Accumulator
pub b: u8,
pub c: u8,
pub d: u8,
pub e: u8,
pub h: u8,
pub l: u8,
pub instr: u8, //Current instruction
pub sp: u16, //Stack pointer
pub pc: u16, //Program counter
pub byte2: u8,
pub byte3: u8,
pub flags: Flags, //Lower bits of AF, Flags register
pub rom_bank_0: [u8; 16384],
pub rom_bank_n: [u8; 16384],
pub external_ram_bank_n: [u8; 8192],
pub wram_bank_0: [u8; 4096],
pub wram_bank_n: [u8; 4096],
}
impl Chip {
pub fn new() -> Self {
Chip {
a: 0,
b: 0,
c: 0,
d: 0,
e: 0,
h: 0,
l: 0,
instr: 0,
sp: 0,
pc: 0,
byte2: 0,
byte3: 0,
flags: Flags::new(),
rom_bank_0: [0; 16384],
rom_bank_n: [0; 16384],
external_ram_bank_n: [00; 8192],
wram_bank_0: [0; 4096],
wram_bank_n: [0; 4096],
}
}
pub fn load_rom(&mut self, rom_path: &str) {
let mut rom_buf = Vec::new();
let mut rom = File::open(rom_path).unwrap_or_else(|_err| panic!("Valid ROM needed!"));
rom.read_to_end(&mut rom_buf).unwrap_or_else(|_err| panic!("Error reading ROM"));
for i in 0..self.rom_bank_0.len() {
self.rom_bank_0[i] = rom_buf.get(i).unwrap().to_owned();
}
self.pc = 0x0100;
}
pub fn write_memory(&mut self, pc: usize, value: u8) {
match pc {
0x0000..=0x3fff => { println!("ROM Bank 0"); self.rom_bank_0[pc as usize] = value }, //Fixed bank, rom_bank_0
0x4000..=0x7fff => { println!("ROM Bank 1"); self.rom_bank_n[pc as usize - 0x4000] = value },
0x8000..=0x9fff => { },
0xa000..=0xbfff => { },
0xc000..=0xcfff => { },
0xd000..=0xdfff => { },
0xfe00..=0xfe9f => { },
0xff00..=0xff7f => { },
0xff80..=0xfffe => { },
0xffff..=0xffff => { },
_ => { }
};
}
pub fn read_memory(&self, pc: usize) -> u8 {
let address = match pc {
0x0000..=0x3fff => { println!("ROM Bank 0"); self.rom_bank_0[pc as usize] }, //Fixed bank, rom_bank_0
0x4000..=0x7fff => { println!("ROM Bank 1"); self.rom_bank_n[pc as usize - 0x4000] },
0x8000..=0x9fff => { 0x0 },
0xa000..=0xbfff => { 0x0 },
0xc000..=0xcfff => { 0x0 },
0xd000..=0xdfff => { 0x0 },
0xfe00..=0xfe9f => { 0x0 },
0xff00..=0xff7f => { 0x0 },
0xff80..=0xfffe => { 0x0 },
0xffff..=0xffff => { 0x0 },
_ => { 0xff }
};
address
}
pub fn fetch(&mut self) {
self.instr = self.read_memory(self.pc as usize);
let arg1 = self.read_memory(self.pc as usize + 1);
let arg2 = self.read_memory(self.pc as usize + 2);
self.byte2 = arg1;
self.byte3 = arg2;
println!("Instr: 0x{:02X}", self.instr);
self.pc += 1;
println!("0x{:02X?}", &self.rom_bank_0[self.pc as usize..(self.pc + 10) as usize]);
}
pub fn execute(&mut self) {
let mut next = 0;
match self.instr {
0x00 => { println!("NOOP!") }
0x32 => { self.ldd_hl_a() }
0x0e | 0x06 => { self.ld_rr(); next = 1; }
0xc3 => { self.jmp_nn() }
0xa8..=0xaf => { self.xor_r() }
0x01 | 0x11 | 0x21 | 0x31 => { self.ld_rr_nn(); next = 2; },
_ => { println!("Error: 0x{:02X} not implemented!", self.instr); std::process::exit(1); }
}
self.pc += next;
}
fn ld_rr(&mut self) {
match self.instr {
0x0e => { self.c = self.byte2 },
0x06 => { self.b = self.byte2 },
_ => {},
}
}
fn ldd_hl_a(&mut self) {
let mut pc = ((self.h as u16) << 8) as u16 | self.l as u16;
self.write_memory(pc as usize, self.a);
pc -= 1;
self.h = (pc >> 8) as u8;
self.l = (pc << 8 >> 8) as u8;
}
fn xor_r(&mut self) {
let value = match self.instr & 0x0f {
0x8 => { self.b },
0x9 => { self.c },
0xa => { self.d },
0xb => { self.e },
0xc => { self.h },
0xd => { self.l },
0xe => {
let ptr = ((self.h as u16) << 8) as u16 | self.l as u16;
self.read_memory(ptr as usize)
},
0xf => { self.a },
_ => { panic!("Wrong register read for XOR_R") }
};
self.a = self.a ^ value;
self.flags.zero = (self.a == 0) as u8
}
fn jmp_nn(&mut self) {
println!("{:02X}, {:02X}", self.byte2, self.byte3);
self.pc = ((self.byte3 as u16) << 8) as u16 | self.byte2 as u16;
println!("Jumping to 0x{:02X}", self.pc);
}
fn ld_rr_nn(&mut self) {
match self.instr {
0x01 => { self.b = self.byte3; self.c = self.byte2; }, //BC = nn (nn = MSB << 8 | LSB)
0x11 => { self.d = self.byte3; self.e = self.byte2; }, //DE = nn (nn = MSB << 8 | LSB)
0x21 => { self.h = self.byte3; self.l = self.byte2; }, //HL = nn (nn = MSB << 8 | LSB)
0x31 => { self.sp = ((self.byte3 as u16) <<
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