static Token()
{
Token token = new Token {
Text = "gt",
Id = TokenId.Identifier,
Position = 0
};
GreaterThan = token;
Token token2 = new Token {
Text = "eq",
Id = TokenId.Identifier,
Position = 0
};
EqualsTo = token2;
Token token3 = new Token {
Text = "lt",
Id = TokenId.Identifier,
Position = 0
};
LessThan = token3;
}
private void ExpandIdentifier(Func<bool> expander, bool ignoreWs)
{
if (this.token.Id == TokenId.Identifier)
{
int textPos = this.textPos;
char ch = this.ch;
Token token = this.token;
bool ignoreWhitespace = this.ignoreWhitespace;
this.ignoreWhitespace = ignoreWs;
int position = this.token.Position;
if (expander())
{
this.token.Text = this.text.Substring(position, this.textPos - position);
this.token.Position = position;
}
else
{
this.textPos = textPos;
this.ch = ch;
this.token = token;
}
this.ignoreWhitespace = ignoreWhitespace;
}
}
/// <summary>Returns the next token without advancing the lexer.</summary>
/// <returns>The next token.</returns>
internal Token PeekNextToken()
{
int savedTextPos = this.textPos;
char savedChar = this.ch;
Token savedToken = this.token;
this.NextToken();
Token result = this.token;
this.textPos = savedTextPos;
this.ch = savedChar;
this.token = savedToken;
return result;
}
/// <summary>Handles -, not unary operators.</summary>
/// <returns>The parsed expression.</returns>
private Expression ParseUnary()
{
this.RecurseEnter();
if (this.CurrentToken.Id == TokenId.Minus || this.CurrentToken.IdentifierIs(ExpressionConstants.KeywordNot))
{
Token op = this.CurrentToken;
this.lexer.NextToken();
if (op.Id == TokenId.Minus && (ExpressionLexer.IsNumeric(this.CurrentToken.Id)))
{
Token numberLiteral = this.CurrentToken;
numberLiteral.Text = "-" + numberLiteral.Text;
numberLiteral.Position = op.Position;
this.CurrentToken = numberLiteral;
this.RecurseLeave();
return this.ParsePrimary();
}
Expression expr = this.ParseUnary();
if (op.Id == TokenId.Minus)
{
this.CheckAndPromoteOperand(typeof(OperationSignatures.INegationSignatures), op.Text, ref expr, op.Position);
expr = GenerateNegate(expr);
}
else
{
this.CheckAndPromoteOperand(typeof(OperationSignatures.INotSignatures), op.Text, ref expr, op.Position);
expr = GenerateNot(expr);
}
this.RecurseLeave();
return expr;
}
this.RecurseLeave();
return this.ParsePrimary();
}
/// <summary>
/// Given left and right hand side expressions, generates a comparison expression based
/// on the given comparison token
/// </summary>
/// <param name="left">Left hand side expression</param>
/// <param name="right">Right hand side expression</param>
/// <param name="op">Comparison operator</param>
/// <returns>Resulting comparison expression</returns>
private Expression GenerateComparisonExpression(Expression left, Expression right, Token op)
{
bool equality = op.IsEqualityOperator;
if (equality && !left.Type.IsValueType && !right.Type.IsValueType)
{
if (left.Type != right.Type)
{
if (WebUtil.IsNullConstant(left))
{
left = Expression.Constant(null, right.Type);
}
else if (WebUtil.IsNullConstant(right))
{
right = Expression.Constant(null, left.Type);
}
else if (left.Type.IsAssignableFrom(right.Type))
{
right = Expression.Convert(right, left.Type);
}
else if (right.Type.IsAssignableFrom(left.Type))
{
left = Expression.Convert(left, right.Type);
}
else
{
throw ExpressionParser.IncompatibleOperandsError(op.Text, left, right, op.Position);
}
}
}
else if (left == WebUtil.NullLiteral || right == WebUtil.NullLiteral)
{
if (!equality)
{
throw ParseError(
Strings.RequestQueryParser_NullOperatorUnsupported(op.Text, op.Position, this.lexer.ExpressionText));
}
// Because we don't have an explicit "is null" check, literal comparisons
// to null are special.
if (!WebUtil.TypeAllowsNull(left.Type))
{
left = Expression.Convert(left, typeof(Nullable<>).MakeGenericType(left.Type));
}
else if (!WebUtil.TypeAllowsNull(right.Type))
{
right = Expression.Convert(right, typeof(Nullable<>).MakeGenericType(right.Type));
}
}
else
{
// Enums should be checked here for promotion when supported, but they aren't in this version.
Debug.Assert(!IsEnumType(left.Type), "!IsEnumType(left.Type)");
Debug.Assert(!IsEnumType(right.Type), "!IsEnumType(right.Type)");
Type signatures = equality ? typeof(OperationSignatures.IEqualitySignatures) : typeof(OperationSignatures.IRelationalSignatures);
this.CheckAndPromoteOperands(signatures, op.Text, ref left, ref right, op.Position);
}
Debug.Assert(op.Id == TokenId.Identifier, "op.id == TokenId.Identifier");
MethodInfo comparisonMethodInfo = null;
if (!equality)
{
if (left.Type == typeof(string))
{
comparisonMethodInfo = StringCompareMethodInfo;
}
else
if (left.Type == typeof(bool))
{
comparisonMethodInfo = BoolCompareMethodInfo;
}
else if (left.Type == typeof(bool?))
{
comparisonMethodInfo = BoolCompareMethodInfoNullable;
}
else
if (left.Type == typeof(Guid))
{
comparisonMethodInfo = GuidCompareMethodInfo;
}
else
if (left.Type == typeof(Guid?))
{
comparisonMethodInfo = GuidCompareMethodInfoNullable;
}
}
switch (op.Text)
{
case ExpressionConstants.KeywordEqual:
left = GenerateEqual(left, right);
break;
case ExpressionConstants.KeywordNotEqual:
left = GenerateNotEqual(left, right);
break;
case ExpressionConstants.KeywordGreaterThan:
left = GenerateGreaterThan(left, right, comparisonMethodInfo);
break;
case ExpressionConstants.KeywordGreaterThanOrEqual:
left = GenerateGreaterThanEqual(left, right, comparisonMethodInfo);
break;
case ExpressionConstants.KeywordLessThan:
left = GenerateLessThan(left, right, comparisonMethodInfo);
break;
case ExpressionConstants.KeywordLessThanOrEqual:
left = GenerateLessThanEqual(left, right, comparisonMethodInfo);
break;
}
return left;
}
/// <summary>
/// Generates a comparison expression which can handle NULL values for any type.
/// NULL is always treated as the smallest possible value.
/// So for example for strings NULL is smaller than any non-NULL string.
/// For now only GreaterThan and LessThan operators are supported by this method.
/// </summary>
/// <param name="left">Left hand side expression</param>
/// <param name="rightLiteral">Literal for the right hand side</param>
/// <param name="op">gt or lt operator token</param>
/// <returns>Resulting comparison expression (has a Boolean value)</returns>
private Expression GenerateNullAwareComparison(Expression left, String rightLiteral, Token op)
{
Debug.Assert(
op.Text == ExpressionConstants.KeywordGreaterThan || op.Text == ExpressionConstants.KeywordLessThan,
"Only GreaterThan or LessThan operators are supported by the GenerateNullAwateComparison method for now.");
ExpressionLexer l = new ExpressionLexer(rightLiteral);
Expression right = this.ParsePrimaryStart(l);
if (WebUtil.TypeAllowsNull(left.Type))
{
if (!WebUtil.TypeAllowsNull(right.Type))
{
right = Expression.Convert(right, typeof(Nullable<>).MakeGenericType(right.Type));
}
}
else if (WebUtil.TypeAllowsNull(right.Type))
{
left = Expression.Convert(left, typeof(Nullable<>).MakeGenericType(left.Type));
}
else
{
// Can't perform NULL aware comparison on this type. Just let the normal
// comparison deal with it. Since the type doesn't allow NULL one should
// never appear, so normal comparison is just fine.
return this.GenerateComparisonExpression(left, right, op);
}
switch (op.Text)
{
case ExpressionConstants.KeywordGreaterThan:
// (left != null) && ((right == null) || Compare(left, right) > 0)
if (left == WebUtil.NullLiteral)
{
return Expression.Constant(false, typeof(bool));
}
else if (right == WebUtil.NullLiteral)
{
return GenerateNotEqual(left, Expression.Constant(null, left.Type));
}
else
{
return GenerateLogicalAnd(
GenerateNotEqual(left, Expression.Constant(null, left.Type)),
GenerateLogicalOr(
GenerateEqual(right, Expression.Constant(null, right.Type)),
this.GenerateComparisonExpression(left, right, op)));
}
case ExpressionConstants.KeywordLessThan:
// (right != null) && ((left == null) || Compare(left, right) < 0)
if (right == WebUtil.NullLiteral)
{
return Expression.Constant(false, typeof(bool));
}
else if (left == WebUtil.NullLiteral)
{
return GenerateNotEqual(right, Expression.Constant(null, right.Type));
}
else
{
return GenerateLogicalAnd(
GenerateNotEqual(right, Expression.Constant(null, left.Type)),
GenerateLogicalOr(
GenerateEqual(left, Expression.Constant(null, right.Type)),
this.GenerateComparisonExpression(left, right, op)));
}
default:
// For now only < and > are supported as we use this only from $skiptoken
throw ParseError(
Strings.RequestQueryParser_NullOperatorUnsupported(op.Text, op.Position, this.lexer.ExpressionText));
}
}
/// <summary>
/// Generates a comparison expression given a left hand side expression and literal for right hand side
/// </summary>
/// <param name="left">Left hand side experssions</param>
/// <param name="rightLiteral">Literal for right hand side</param>
/// <param name="op">gt, eq or lt operator token</param>
/// <returns>Resulting comparison expression</returns>
private Expression GenerateComparison(Expression left, String rightLiteral, Token op)
{
ExpressionLexer l = new ExpressionLexer(rightLiteral);
return this.GenerateComparisonExpression(left, this.ParsePrimaryStart(l), op);
}
/// <summary>Checks that the given token has the specified identifier.</summary>
/// <param name="token">Token to check</param>
/// <param name="id">Identifier to check.</param>
/// <returns>true if <paramref name="token"/> is an identifier with the specified text.</returns>
private static bool TokenIdentifierIs(Token token, string id)
{
return token.Id == TokenId.Identifier && String.Equals(id, token.Text, StringComparison.OrdinalIgnoreCase);
}
internal Token PeekNextToken()
{
int textPos = this.textPos;
char ch = this.ch;
Token token = this.token;
this.NextToken();
Token token2 = this.token;
this.textPos = textPos;
this.ch = ch;
this.token = token;
return token2;
}
