add simple assembler

1 files changed, 73 insertions, 0 deletions

diff --git a/src/assembler.rs b/src/assembler.rs
new file mode 100644
index 0000000..3cd2bf8
--- /dev/null
+++ b/src/assembler.rs
@@ -0,0 +1,73 @@
+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
+}