// 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); }