arnaucube/chip8-rs
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u8 operations with wrapping to avoid overflow

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arnaucube
2020-10-19 20:44:08 +02:00
parent d68feb1fd9
commit 0d75e866a9
7 changed files with 40 additions and 29 deletions
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35
chip8/src/lib.rs
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@@ -15,7 +15,7 @@ pub struct Chip8 {
delay_timer: u8,
sound_timer: u8,
stack: [u16; 16],
sp: isize,
sp: usize,
pub key: [u8; 16],
pub draw_flag: bool,
}
@@ -77,7 +77,7 @@ impl Chip8 {
let y: usize = ((self.opcode & 0x00F0) >> 4) as usize;
let nn: u8 = (self.opcode & 0x00FF) as u8;
let nnn: u16 = (self.opcode & 0x0FFF) as u16;
// println!("{:?} {:?}", self.opcode, self.pc);
// println!("{:x} {:?}", self.opcode, self.pc);
// Decode Opcode
// https://en.wikipedia.org/wiki/CHIP-8#Opcode_table
@@ -95,10 +95,10 @@ impl Chip8 {
0x000E => {
// 00EE Returns from a subroutine
self.sp -= 1;
self.pc = self.stack[self.sp as usize];
self.pc = self.stack[self.sp];
self.pc += 2;
}
_ => println!("unk {:x}", self.opcode),
_ => println!("Unknown opcode: {:x}", self.opcode),
}
}
0x1000 => {
@@ -107,7 +107,7 @@ impl Chip8 {
}
0x2000 => {
// 2NNN Calls subroutine at NNN
self.stack[self.sp as usize] = self.pc;
self.stack[self.sp] = self.pc;
self.sp += 1;
self.pc = nnn;
}
@@ -143,7 +143,7 @@ impl Chip8 {
}
0x7000 => {
// 7XNN Adds NN to VX. (Carry flag is not changed)
self.v[x] += nn;
self.v[x] = self.v[x].wrapping_add(nn);
self.pc += 2;
}
0x8000 => {
@@ -176,7 +176,7 @@ impl Chip8 {
} else {
self.v[0xF] = 0;
}
self.v[x] += self.v[y];
self.v[x] = self.v[x].wrapping_add(self.v[y]);
self.pc += 2;
}
0x0005 => {
@@ -187,7 +187,7 @@ impl Chip8 {
} else {
self.v[0xF] = 0;
}
self.v[x] -= self.v[y];
self.v[x] = self.v[x].wrapping_sub(self.v[y]);
self.pc += 2;
}
0x0006 => {
@@ -198,7 +198,7 @@ impl Chip8 {
} else {
self.v[0xF] = 0;
}
self.v[x] = self.v[x] >> 1;
self.v[x] = self.v[x].wrapping_shr(1);
self.pc += 2;
}
0x0007 => {
@@ -209,7 +209,7 @@ impl Chip8 {
} else {
self.v[0xF] = 0;
}
self.v[x] = self.v[y] - self.v[x];
self.v[x] = self.v[y].wrapping_sub(self.v[x]);
self.pc += 2;
}
0x000E => {
@@ -220,10 +220,10 @@ impl Chip8 {
} else {
self.v[0xF] = 0;
}
self.v[x] = self.v[x] << 1;
self.v[x] = self.v[x].wrapping_shl(1);
self.pc += 2;
}
_ => println!("unk {:x}", self.opcode),
_ => println!("Unknown opcode: {:x}", self.opcode),
}
}
0x9000 => {
@@ -243,7 +243,7 @@ impl Chip8 {
0xB000 => {
// BNNN Jumps to the address NNN plus V0
self.pc = nnn + self.v[0] as u16;
self.pc += 2;
// self.pc += 2;
}
0xC000 => {
// CXNN Sets VX to the result of a bitwise and operation on a
@@ -275,9 +275,8 @@ impl Chip8 {
}
if self.gfx[pos] == 1 {
self.v[0xF] = 1;
} else {
self.gfx[pos] ^= 1;
}
self.gfx[pos] ^= 1;
}
}
}
@@ -305,7 +304,7 @@ impl Chip8 {
}
self.pc += 2;
}
_ => println!("unk {:x}", self.opcode),
_ => println!("Unknown opcode: {:x}", self.opcode),
}
}
0xF000 => {
@@ -378,10 +377,10 @@ impl Chip8 {
}
self.pc += 2;
}
_ => println!("unk {:x}", self.opcode),
_ => println!("Unknown opcode: {:x}", self.opcode),
}
}
_ => println!("opc {:x}", self.opcode),
_ => println!("Unknown opcode: {:x}", self.opcode),
}
if self.delay_timer > 0 {
self.delay_timer -= 1;