Started work on parser.

src/MOS/6502/assembler/parser.js

@@ -0,0 +1,106 @@
+
+function TokenStream(input){
+  var pos = 0;
+
+  function peek(){
+    return input[pos];
+  }
+
+  function next(){
+    let v = input[pos];
+    pos += 1;
+    return v;
+  }
+
+  function line(){
+    return (pos < input.length) ? input[pos].line : -1;
+  }
+
+  function col(){
+    return (pos < input.length) ? input[pos].col : -1;
+  }
+
+  function eof(){
+    return (pos >= input.length);
+  }
+
+  function die(msg){
+    throw new Error(msg + " Line: " + input[pos].line + ", Col: " + input[pos].col);
+  }
+
+  return {
+    peek: peek,
+    next: next,
+    line: line,
+    col: col,
+    eof, eof,
+    die: die
+  };
+}
+
+
+var stream = null;
+
+
+parseDirective(){
+  let d = stream.next();
+  let args = [];
+  while (stream.peek().line === d.line){
+    let a = stream.next();
+    switch(a.type){
+      case "number":
+        // TODO: Check if math ops are called.
+      case "string":
+        args.push(a);
+        break;
+      case "label":
+        args.push({
+          type: "var",
+          val: a.val,
+          line: a.line,
+          col: a.col
+        });
+        break;
+      case "punc":
+        // Ignore punctuations!
+        break;
+      default:
+        stream.die("Invalid token '" + a.type + "'.");
+    }
+  }
+
+  return {
+    type: 'directive',
+    args: args,
+    line: d.line,
+    col: d.col
+  };
+}
+
+parseExpression(){
+  o = stream.peek();
+  if (o.type === 'directive'){
+    return parseDirective();
+  }
+}
+
+parse(tokens){
+  let p = {
+    type: "prog",
+    expressions: [];
+  };
+  stream = TokenStream(tokens);
+  while (!stream.eof()){
+    p.expressions.push(parseExpression());
+  }
+  stream = null;
+  return p;
+}
+
+
+module.exports = Object.freeze({
+  parse: parse
+});
+
+
+