public BaseExpression Parse(string source)
{
var tokenizer = new Tokenizer();
var tokens = tokenizer.Read(source);
var queue = new TokensQueue(tokens);
return Parse(queue);
}
public IList<BaseExpression> ParseArguments(TokensQueue tokens)
{
var res = new List<BaseExpression>();
while (!tokens.IsEndOfLine) {
var preview = tokens.Peek();
if (preview.Type == TokenType.CloseParenthesis) return res;
var arg = Parse(tokens);
res.Add(arg);
preview = tokens.Peek();
if (preview.Type != TokenType.Comma) break;
tokens.Read(TokenType.Comma);
}
return res;
}
protected BaseExpression ParseLiteral(Token token, TokensQueue queue)
{
if (queue.Count > 0) {
var preview = queue.Peek();
if (preview.Type == TokenType.OpenParenthesis) {
return Func(token, queue);
}
}
if (token.StringValue == "$") {
return new NumberExpression { Value = _context.Offset };
}
var lblValue = _context.GetLabel(token);
if (lblValue == null) {
throw new TokenException("unknown symbol " + token.StringValue, token);
}
return new NumberExpression { Value = (long)lblValue };
}
protected BaseExpression Func(Token nameToken, TokensQueue tokens)
{
tokens.Read(TokenType.OpenParenthesis);
var args = ParseArguments(tokens);
tokens.Read(TokenType.CloseParenthesis);
switch (nameToken.StringValue.ToLower()) {
case "low":
if (args.Count != 1) {
throw new TokenException("expected 1 argument", nameToken);
}
return new LowByteExpression(args.First());
case "high":
if (args.Count != 1) {
throw new TokenException("expected 1 argument", nameToken);
}
return new HighByteExpression(args.First());
default:
throw new TokenException("unknown function " + nameToken.StringValue, nameToken);
}
}
public BaseExpression Parse(TokensQueue tokens)
{
return ParseWithPriority(tokens, 0);
}
private BaseExpression ProcessBinaryExpression(Token opToken, BaseExpression left, TokensQueue tokens)
{
var tokenPriority = GetPriority(opToken.Type);
var other = ParseWithPriority(tokens, tokenPriority + 1);
switch (opToken.Type) {
case TokenType.Plus: return new AddExpression(left, other);
case TokenType.Minus: return new SubExpression(left, other);
case TokenType.Multiply: return new MulExpression(left, other);
case TokenType.Divide: return new DivExpression(left, other);
case TokenType.Mod: return new ModExpression(left, other);
case TokenType.LeftShift: return new ShiftLeftExpression(left, other);
case TokenType.RightShift: return new ShiftRightExpression(left, other);
case TokenType.BitOr: return new BitOrExpression(left, other);
case TokenType.BitAnd: return new BitAndExpression(left, other);
case TokenType.BitXor: return new BitXorExpression(left, other);
default:
throw new TokenException("unexpected operator", opToken);
}
}
private BaseExpression ParseWithPriority(TokensQueue tokens, int priority)
{
BaseExpression left = ParseOperand(tokens);
while (tokens.Count > 0) {
var preview = tokens.Peek();
switch (preview.Type) {
case TokenType.NewLine:
case TokenType.Comma:
case TokenType.CloseParenthesis:
return left;
}
var tokenPriority = GetPriority(preview.Type);
if (tokenPriority >= 0 && tokenPriority < priority) {
if (left != null) return left;
throw new Exception("some case");
}
var token = tokens.Read();
switch (token.Type) {
case TokenType.Plus:
case TokenType.Minus:
case TokenType.Multiply:
case TokenType.Divide:
case TokenType.Mod:
case TokenType.LeftShift:
case TokenType.RightShift:
case TokenType.BitOr:
case TokenType.BitAnd:
case TokenType.BitXor:
left = ProcessBinaryExpression(token, left, tokens);
break;
default:
throw new TokenException("unexpected token " + token.StringValue, token);
}
}
return left;
}
private BaseExpression ParseOperand(TokensQueue tokens)
{
if (tokens.IsEndOfLine) {
throw new TokenException("operand expected", tokens.LastReadToken);
}
var token = tokens.Read();
switch (token.Type) {
case TokenType.Integer: return new NumberExpression { Value = token.IntegerValue };
case TokenType.Literal: return ParseLiteral(token, tokens);
case TokenType.NewLine: throw new TokenException("value expected", token);
case TokenType.Minus: return new NegateExpression(ParseOperand(tokens));
case TokenType.OpenParenthesis:
var inner = Parse(tokens);
if (tokens.IsEndOfLine) {
throw new TokenException("missing closing parenthesis", tokens.LastReadToken);
}
tokens.Read(TokenType.CloseParenthesis);
return inner;
default:
throw new TokenException("unexpected token " + token.StringValue, token);
}
}
