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use crate::instructions::Instruction;
fn tokenize(line: &str) -> Vec<String> {
line.split(|c| c == ' ' || c == ',' || c == '\t')
.filter(|s| !s.is_empty())
.map(|s| s.to_lowercase())
.collect()
}
fn parse_reg(s: &str) -> u8 {
match s {
"a" => 0,
"b" => 1,
"c" => 2,
"d" => 3,
_ => panic!("Unknown register {}", s),
}
}
pub fn assembler(source: &str) -> Vec<u8> {
let mut bytes = Vec::new();
for (line_no, line) in source.lines().enumerate() {
let line = line.trim();
// Comments in assembly start with ";"
if line.is_empty() || line.starts_with(';') {
continue;
}
let tokens = tokenize(line);
match tokens[0].as_str() {
"mov" => {
// mov reg, imm
let reg = parse_reg(&tokens[1]);
let imm: u8 = tokens[2].parse().unwrap();
bytes.push(Instruction::MOV as u8);
bytes.push(reg);
bytes.push(imm);
}
"add" => {
// add a, b
let r1 = parse_reg(&tokens[1]);
let r2 = parse_reg(&tokens[2]);
bytes.push(Instruction::ADD as u8);
bytes.push(r1);
bytes.push(r2);
}
"sub" => {
// sub a, b
let r1 = parse_reg(&tokens[1]);
let r2 = parse_reg(&tokens[2]);
bytes.push(Instruction::SUB as u8);
bytes.push(r1);
bytes.push(r2);
}
"hlt" => {
bytes.push(Instruction::HLT as u8);
}
_ => panic!("Line {}: unknown instruction", line_no + 1),
}
}
bytes
}
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