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remove get_byte_mut_ref method from Memory 

This is the right thing to do, because the actual hardware will perform
a read and then perform a write. This could have observable side effects
on a real system
This commit is contained in:
Sam M W 2023-04-02 21:35:18 +01:00
parent 766143d52f
commit 131b0f312d
2 changed files with 18 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
src/cpu.rs
View File

@ -103,10 +103,9 @@ impl CPU {
self.registers.accumulator = val as i8;
}
(Instruction::ASL, OpInput::UseAddress(addr)) => {
CPU::shift_left_with_flags(
self.memory.get_byte_mut_ref(addr),
&mut self.registers.status,
);
let mut operand: u8 = self.memory.get_byte(addr);
CPU::shift_left_with_flags(&mut operand, &mut self.registers.status);
self.memory.set_byte(addr, operand);
}
(Instruction::BCC, OpInput::UseRelative(rel)) => {
@ -208,10 +207,9 @@ impl CPU {
}
(Instruction::DEC, OpInput::UseAddress(addr)) => {
CPU::decrement(
self.memory.get_byte_mut_ref(addr),
&mut self.registers.status,
);
let mut operand: u8 = self.memory.get_byte(addr);
CPU::decrement(&mut operand, &mut self.registers.status);
self.memory.set_byte(addr, operand);
}
(Instruction::DEY, OpInput::UseImplied) => {
@ -231,10 +229,9 @@ impl CPU {
}
(Instruction::INC, OpInput::UseAddress(addr)) => {
CPU::increment(
self.memory.get_byte_mut_ref(addr),
&mut self.registers.status,
);
let mut operand: u8 = self.memory.get_byte(addr);
CPU::increment(&mut operand, &mut self.registers.status);
self.memory.set_byte(addr, operand);
}
(Instruction::INX, OpInput::UseImplied) => {
CPU::increment(&mut self.registers.index_x, &mut self.registers.status);
@ -282,10 +279,9 @@ impl CPU {
self.registers.accumulator = val as i8;
}
(Instruction::LSR, OpInput::UseAddress(addr)) => {
CPU::shift_right_with_flags(
self.memory.get_byte_mut_ref(addr),
&mut self.registers.status,
);
let mut operand: u8 = self.memory.get_byte(addr);
CPU::shift_right_with_flags(&mut operand, &mut self.registers.status);
self.memory.set_byte(addr, operand);
}
(Instruction::ORA, OpInput::UseImmediate(val)) => {
@ -327,10 +323,9 @@ impl CPU {
self.registers.accumulator = val as i8;
}
(Instruction::ROL, OpInput::UseAddress(addr)) => {
CPU::rotate_left_with_flags(
self.memory.get_byte_mut_ref(addr),
&mut self.registers.status,
);
let mut operand: u8 = self.memory.get_byte(addr);
CPU::rotate_left_with_flags(&mut operand, &mut self.registers.status);
self.memory.set_byte(addr, operand);
}
(Instruction::ROR, OpInput::UseImplied) => {
// Accumulator mode
@ -339,10 +334,9 @@ impl CPU {
self.registers.accumulator = val as i8;
}
(Instruction::ROR, OpInput::UseAddress(addr)) => {
CPU::rotate_right_with_flags(
self.memory.get_byte_mut_ref(addr),
&mut self.registers.status,
);
let mut operand: u8 = self.memory.get_byte(addr);
CPU::rotate_right_with_flags(&mut operand, &mut self.registers.status);
self.memory.set_byte(addr, operand);
}
(Instruction::SBC, OpInput::UseImmediate(val)) => {

4
src/memory.rs
View File

@ -69,10 +69,6 @@ impl Memory {
self.bytes[address as usize]
}
pub fn get_byte_mut_ref(&mut self, address: u16) -> &mut u8 {
&mut self.bytes[address as usize]
}
pub fn get_slice(&self, start: u16, diff: u16) -> &[u8] {
let orig: usize = start.into();
let end = orig + diff as usize;