// Move to the next token
// This updates the values in the token instance and returns true if successful.
internal bool MoveNext()
{
// Hold onto the ID of the last token.
// It will be needed by some of the special cases.
this.previousID = this.token.TokenID;
// If there are no more characters, we can't get another token.
if (!AdvanceChar())
{
return(false);
}
if (XPathCharTypes.IsNCNameStart(this.ch))
{
// Extract a QName if we've got the start of an NCName
TokenizeQName();
}
else if (XPathCharTypes.IsDigit(this.ch))
{
// Extract a number
TokenizeNumber();
}
else
{
// Everything else is a single/double character token, or a variable.
switch (this.ch)
{
case '(':
token.Set(XPathTokenID.LParen);
break;
case ')':
token.Set(XPathTokenID.RParen);
break;
case '[':
token.Set(XPathTokenID.LBracket);
break;
case ']':
token.Set(XPathTokenID.RBracket);
break;
case '.':
// Watch for a double period
if (PeekChar() == '.')
{
AdvanceChar();
token.Set(XPathTokenID.DblPeriod);
}
else
{
// Check if the period is the start of a number
if (XPathCharTypes.IsDigit(PeekChar()))
{
TokenizeNumber();
}
else
{
token.Set(XPathTokenID.Period);
}
}
break;
case '@':
token.Set(XPathTokenID.AtSign);
break;
case ',':
token.Set(XPathTokenID.Comma);
break;
case ':':
// Only a double colon is permitted.
// The single colon part of the QName is consumed in TokenizeQName if it is valid
if (PeekChar() == ':')
{
AdvanceChar();
token.Set(XPathTokenID.DblColon);
}
else
{
ThrowError(QueryCompileError.UnexpectedToken, CurrentSubstring());
}
break;
case '/':
// Check for a double slash
if (PeekChar() == '/')
{
AdvanceChar();
token.Set(XPathTokenID.DblSlash);
}
else
{
token.Set(XPathTokenID.Slash);
}
break;
case '|':
token.Set(XPathTokenID.Pipe);
break;
case '+':
token.Set(XPathTokenID.Plus);
break;
case '-':
token.Set(XPathTokenID.Minus);
break;
case '=':
token.Set(XPathTokenID.Eq);
break;
case '!':
// This can only be the start of a '!='
// 'not' is a negation in XPath
if (PeekChar() == '=')
{
AdvanceChar();
token.Set(XPathTokenID.Neq);
}
else
{
ThrowError(QueryCompileError.UnsupportedOperator, CurrentSubstring());
}
break;
case '<':
// Watch for '<='
if (PeekChar() == '=')
{
AdvanceChar();
token.Set(XPathTokenID.Lte);
}
else
{
token.Set(XPathTokenID.Lt);
}
break;
case '>':
// Watch for '>='
if (PeekChar() == '=')
{
AdvanceChar();
token.Set(XPathTokenID.Gte);
}
else
{
token.Set(XPathTokenID.Gt);
}
break;
case '*':
// Check if we're supposed to parse a '*' as a multiply
if (IsSpecialPrev())
{
token.Set(XPathTokenID.Multiply);
}
else
{
token.Set(XPathTokenID.Wildcard, new XPathParser.QName(string.Empty, QueryDataModel.Wildcard));
}
break;
case '$':
// Make sure '$' was followed by something that counts as a variable name
XPathParser.QName qname = GetQName();
if (qname.Prefix.Length == 0 && qname.Name.Length == 0)
{
AdvanceChar();
ThrowError(QueryCompileError.InvalidVariable, this.ch == char.MinValue ? string.Empty : CurrentSubstring());
}
token.Set(XPathTokenID.Variable, qname);
break;
case '\"':
TokenizeLiteral('\"');
break;
case '\'':
TokenizeLiteral('\'');
break;
default:
// Unrecognized character
token.Set(XPathTokenID.Unknown);
break;
}
}
// Whitespace can mark the end of a token, but is not part of the XPath syntax
ConsumeWhitespace();
return(true);
}