private Token Number()
{
SkipWhitespaces();
if (_source.IsEndOfFile)
{
return null;
}
Token token = null;
var state = NumberParseState.InPrimaryPart;
using (var lookahead = _source.BeginLookahead())
{
_buffer.Clear();
var startPosition = _source.Position;
while (!_source.IsEndOfFile)
{
var ch = _source.Peek();
if (char.IsDigit(ch))
{
if (state == NumberParseState.BeginFractionalPart)
{
state = NumberParseState.InFractionalPart;
}
_buffer.Append(ch);
_source.MoveNext();
if (_source.IsEndOfFile && (state == NumberParseState.InPrimaryPart || state == NumberParseState.InFractionalPart))
{
lookahead.Accept();
token = new Token(_buffer.ToString(), TokenKind.Number, new SourceLocation(startPosition));
break;
}
}
else if (ch == '.')
{
state = NumberParseState.BeginFractionalPart;
_buffer.Append(ch);
_source.MoveNext();
}
else
{
if (state == NumberParseState.BeginFractionalPart)
{
_context.AddError("Missing fractional part.", new SourceLocation(_source.Position));
break;
}
else
{
lookahead.Accept();
token = new Token(_buffer.ToString(), TokenKind.Number, new SourceLocation(startPosition));
break;
}
}
}
}
return token;
}
private Token Identifier()
{
_source.SkipWhile(char.IsWhiteSpace);
if (_source.IsEndOfFile)
{
return null;
}
_buffer.Clear();
Token token = null;
using (var lookahead = _source.BeginLookahead())
{
var startPosition = _source.Position;
var ch = _source.Read();
// identifier must start with a letter or _
if (char.IsLetter(ch) || ch == '_')
{
_buffer.Append(ch);
while (!_source.IsEndOfFile)
{
ch = _source.Peek();
// We will allow '.' char, because we want to allow this parameter syntax: Order.BillingAddress.Country
if (char.IsDigit(ch) || char.IsLetter(ch) || ch == '_' || ch == '.')
{
_buffer.Append(ch);
_source.MoveNext();
}
else
{
lookahead.Accept();
var tokenValue = _buffer.ToString();
var tokenKind = TokenKind.Identifier;
if (tokenValue.Equals("AND", StringComparison.OrdinalIgnoreCase))
{
tokenKind = TokenKind.AND;
}
else if (tokenValue.Equals("OR", StringComparison.OrdinalIgnoreCase))
{
tokenKind = TokenKind.OR;
}
token = new Token(tokenValue, tokenKind, new SourceLocation(startPosition));
break;
}
}
}
}
return token;
}