private void SkipWhiteSpace(ExpressionTokenParser parser)
{
var pt = parser.Peek();
while (pt?.TokenPeek != null && pt.TokenPeek.TokenName == ExpressionTokenParser.Tokens.Whitespace)
{
parser.GetToken();
pt = parser.Peek();
}
}
private ushort ParseExpression(string exp, bool labelScan)
{
var parser = new ExpressionTokenParser { InputString = exp };
var values = new Stack<ushort>();
var operators = new Stack<ExpressionTokenParser.Tokens>();
SkipWhiteSpace(parser);
var token = parser.GetToken();
while (token != null)
{
SkipWhiteSpace(parser);
if (token.TokenName == ExpressionTokenParser.Tokens.Integer ||
token.TokenName == ExpressionTokenParser.Tokens.HexNumber ||
token.TokenName == ExpressionTokenParser.Tokens.HexNumber ||
token.TokenName == ExpressionTokenParser.Tokens.Identifier)
{
ushort val;
switch (token.TokenName)
{
case ExpressionTokenParser.Tokens.HexNumber:
val = ushort.Parse(token.TokenValue.Remove(0, 1), System.Globalization.NumberStyles.HexNumber);
break;
case ExpressionTokenParser.Tokens.BinaryNumber:
val = Convert.ToUInt16(token.TokenValue.Remove(0, 1), 2);
break;
case ExpressionTokenParser.Tokens.Identifier:
if (!_equateTable.ContainsKey(token.TokenValue.Trim().ToUpper()))
{
if (!labelScan)
throw new Exceptions.UndefinedLabelException(
$"The label {token.TokenValue.Trim().ToUpper()} has not been defined, at line {_lineNumber}!");
}
val = _equateTable.ContainsKey(token.TokenValue.Trim().ToUpper())
? _equateTable[token.TokenValue.Trim().ToUpper()]
: (ushort)0;
break;
default:
val = ushort.Parse(token.TokenValue);
break;
}
values.Push(val);
}
else if (token.TokenName == ExpressionTokenParser.Tokens.Lparen)
{
operators.Push(token.TokenName);
}
else if (token.TokenName == ExpressionTokenParser.Tokens.Rparen)
{
while (operators.Peek() != ExpressionTokenParser.Tokens.Lparen)
{
values.Push(ApplyOperation(operators.Pop(), values.Pop(), values.Pop()));
}
operators.Pop();
}
else if (token.TokenName == ExpressionTokenParser.Tokens.Plus ||
token.TokenName == ExpressionTokenParser.Tokens.Minus ||
token.TokenName == ExpressionTokenParser.Tokens.Asterisk)
{
while (operators.Count > 0 && HasPrecedence(token.TokenName, operators.Peek()))
{
if (values.Count == 0) values.Push(0);
values.Push(ApplyOperation(operators.Pop(), values.Pop(), values.Pop()));
}
operators.Push(token.TokenName);
}
SkipWhiteSpace(parser);
token = parser.GetToken();
}
while (operators.Count > 0)
{
values.Push(ApplyOperation(operators.Pop(), values.Pop(), values.Pop()));
}
return values.Pop();
}
