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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2015 Saxonica Limited.
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.expr;
import net.sf.saxon.expr.parser.*;
import net.sf.saxon.expr.sort.AtomicComparer;
import net.sf.saxon.expr.sort.DoubleSortComparer;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.BuiltInAtomicType;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.value.BooleanValue;
import net.sf.saxon.value.Int64Value;
import net.sf.saxon.value.NumericValue;
/**
* This class implements a comparison of a numeric value to an integer constant using one of the operators
* eq, ne, lt, gt, le, ge. The semantics are identical to ValueComparison, but this is a fast path for an
* important common case.
*/
public class CompareToIntegerConstant extends UnaryExpression implements ComparisonExpression {
private long comparand;
private int operator;
/**
* Create the expression
*
* @param operand the operand to be compared with an integer constant. This must
* have a static type of NUMERIC, and a cardinality of EXACTLY ONE
* @param operator the comparison operator,
* one of {@link Token#FEQ}, {@link Token#FNE}, {@link Token#FGE},
* {@link Token#FGT}, {@link Token#FLE}, {@link Token#FLT}
* @param comparand the integer constant
*/
public CompareToIntegerConstant(Expression operand, int operator, long comparand) {
super(operand);
this.operator = operator;
this.comparand = comparand;
}
@Override
protected OperandRole getOperandRole() {
return OperandRole.SINGLE_ATOMIC;
}
public Expression getLhsExpression() {
return getBaseExpression();
}
public Operand getLhs() {
return getOperand();
}
public Expression getRhsExpression() {
return new Literal(new Int64Value(comparand));
}
public Operand getRhs() {
return new Operand(this, getRhsExpression(), OperandRole.SINGLE_ATOMIC);
}
/**
* Get the integer value on the rhs of the expression
*
* @return the integer constant
*/
public long getComparand() {
return comparand;
}
/**
* Get the comparison operator
*
* @return one of {@link Token#FEQ}, {@link Token#FNE}, {@link Token#FGE},
* {@link Token#FGT}, {@link Token#FLE}, {@link Token#FLT}
*/
public int getComparisonOperator() {
return operator;
}
/**
* An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
* This method indicates which of these methods is provided directly. The other methods will always be available
* indirectly, using an implementation that relies on one of the other methods.
*
* @return the value {@link #EVALUATE_METHOD}
*/
public int getImplementationMethod() {
return EVALUATE_METHOD;
}
public int computeSpecialProperties() {
return StaticProperty.NON_CREATIVE;
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
/*@NotNull*/
public Expression copy() {
CompareToIntegerConstant c2 = new CompareToIntegerConstant(getLhsExpression().copy(), operator, comparand);
ExpressionTool.copyLocationInfo(this, c2);
return c2;
}
/**
* Is this expression the same as another expression?
*
* @param other the expression to be compared with this one
* @return true if the two expressions are statically equivalent
*/
@Override
public boolean equals(Object other) {
return other instanceof CompareToIntegerConstant && ((CompareToIntegerConstant)other).getLhsExpression().equals(getLhsExpression())
&& ((CompareToIntegerConstant)other).comparand == comparand
&& ((CompareToIntegerConstant)other).operator == operator;
}
/**
* Hashcode supporting equals()
*/
public int hashCode() {
int h = 0x836b12a0;
return h + getLhsExpression().hashCode() ^ (int)comparand;
}
/**
* Evaluate an expression as a single item. This always returns either a single Item or
* null (denoting the empty sequence). No conversion is done. This method should not be
* used unless the static type of the expression is a subtype of "item" or "item?": that is,
* it should not be called if the expression may return a sequence. There is no guarantee that
* this condition will be detected.
*
* @param context The context in which the expression is to be evaluated
* @return the node or atomic value that results from evaluating the
* expression; or null to indicate that the result is an empty
* sequence
* @throws net.sf.saxon.trans.XPathException
* if any dynamic error occurs evaluating the
* expression
*/
public BooleanValue evaluateItem(XPathContext context) throws XPathException {
return BooleanValue.get(effectiveBooleanValue(context));
}
/**
* Get the effective boolean value of the expression. This returns false if the value
* is the empty sequence, a zero-length string, a number equal to zero, or the boolean
* false. Otherwise it returns true.
*
* @param context The context in which the expression is to be evaluated
* @return the effective boolean value
* @throws net.sf.saxon.trans.XPathException
* if any dynamic error occurs evaluating the
* expression
*/
public boolean effectiveBooleanValue(XPathContext context) throws XPathException {
NumericValue n = (NumericValue) getLhsExpression().evaluateItem(context);
if (n.isNaN()) {
return operator == Token.FNE;
}
int c = n.compareTo(comparand);
switch (operator) {
case Token.FEQ:
return c == 0;
case Token.FNE:
return c != 0;
case Token.FGT:
return c > 0;
case Token.FLT:
return c < 0;
case Token.FGE:
return c >= 0;
case Token.FLE:
return c <= 0;
default:
throw new UnsupportedOperationException("Unknown operator " + operator);
}
}
public int computeCardinality() {
return StaticProperty.EXACTLY_ONE;
}
/**
* Perform optimisation of an expression and its subexpressions. This is the third and final
* phase of static optimization.
*
* This method is called after all references to functions and variables have been resolved
* to the declaration of the function or variable, and after all type checking has been done.
*
* @param visitor the expression visitor
* @param contextInfo the static type of "." at the point where this expression is invoked.
* The parameter is set to null if it is known statically that the context item will be undefined.
* If the type of the context item is not known statically, the argument is set to
* {@link net.sf.saxon.type.Type#ITEM_TYPE}
* @return the original expression, rewritten if appropriate to optimize execution
* @throws XPathException if an error is discovered during this phase
* (typically a type error)
*/
/*@NotNull*/
public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
optimizeChildren(visitor, contextInfo);
if (getLhsExpression() instanceof Literal) {
Literal lit = Literal.makeLiteral(BooleanValue.get(effectiveBooleanValue(null)));
ExpressionTool.copyLocationInfo(this, lit);
return lit;
}
return this;
}
/**
* Determine the data type of the expression, if possible. All expression return
* sequences, in general; this method determines the type of the items within the
* sequence, assuming that (a) this is known in advance, and (b) it is the same for
* all items in the sequence.
*
* This method should always return a result, though it may be the best approximation
* that is available at the time.
*
* @return a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER,
* Type.NODE, or Type.ITEM (meaning not known at compile time)
*/
/*@NotNull*/
public ItemType getItemType() {
return BuiltInAtomicType.BOOLEAN;
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public void export(ExpressionPresenter destination) {
destination.startElement("compareToInt", this);
destination.emitAttribute("op", Token.tokens[operator]);
destination.emitAttribute("val", comparand + "");
getLhsExpression().export(destination);
destination.endElement();
}
/**
* The toString() method for an expression attempts to give a representation of the expression
* in an XPath-like form.
*
* For subclasses of Expression that represent XPath expressions, the result should always be a string that
* parses as an XPath 3.0 expression
*
* @return a representation of the expression as a string
*/
@Override
public String toString() {
return ExpressionTool.parenthesize(getLhsExpression()) + " " +
Token.tokens[operator] + " " + comparand;
}
/**
* Produce a short string identifying the expression for use in error messages
*
* @return a short string, sufficient to identify the expression
*/
@Override
public String toShortString() {
return getLhsExpression().toShortString() + " " + Token.tokens[operator] + " " + comparand;
}
/**
* Get the AtomicComparer used to compare atomic values. This encapsulates any collation that is used
*/
public AtomicComparer getAtomicComparer() {
return DoubleSortComparer.getInstance();
// Note: this treats NaN=NaN as true, but it doesn't matter, because the rhs will never be NaN.
}
/**
* Get the primitive (singleton) operator used: one of Token.FEQ, Token.FNE, Token.FLT, Token.FGT,
* Token.FLE, Token.FGE
*/
public int getSingletonOperator() {
return operator;
}
/**
* Determine whether untyped atomic values should be converted to the type of the other operand
*
* @return true if untyped values should be converted to the type of the other operand, false if they
* should be converted to strings.
*/
public boolean convertsUntypedToOther() {
return true;
}
}
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