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add better error reporting to fetch stage

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This commit is contained in:
Denis-Cosmin NUTIU 2024-12-01 23:11:50 +02:00
parent 6721857320
commit 3f24509955
1 changed files with 12 additions and 6 deletions
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16
src/emulator.rs
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@ -101,10 +101,12 @@ where
fn emulation_loop<T>(&mut self) -> Result<(), anyhow::Error> { fn emulation_loop<T>(&mut self) -> Result<(), anyhow::Error> {
loop { loop {
// fetch instruction // fetch instruction
let instruction = self.fetch_instruction(); let instruction = self.fetch_instruction()?;
self.program_counter += 2; self.program_counter += 2;
// decode opcode debug!("PC={} {:04x}", self.program_counter, instruction)
// decode & execute
//let decode = self.decode_instruction(instruction); //let decode = self.decode_instruction(instruction);
// execute // execute
@ -113,11 +115,15 @@ where
} }
/// Fetches the current instruction from the memory without incrementing the program counter. /// Fetches the current instruction from the memory without incrementing the program counter.
fn fetch_instruction(&self) -> Instruction { fn fetch_instruction(&self) -> Result<Instruction, anyhow::Error> {
Instruction::new([ if self.program_counter as usize >= self.memory.len() {
return Err(anyhow!("program_counter is out of range"));
}
Ok(Instruction::new([
self.memory[self.program_counter as usize], self.memory[self.program_counter as usize],
self.memory[self.program_counter as usize + 1], self.memory[self.program_counter as usize + 1],
]) ]))
} }
fn decode_instruction(&mut self, _instruction: Instruction) -> Result<(), anyhow::Error> { fn decode_instruction(&mut self, _instruction: Instruction) -> Result<(), anyhow::Error> {