package client.net.sf.saxon.ce.expr.sort;
import client.net.sf.saxon.ce.expr.XPathContext;
import client.net.sf.saxon.ce.lib.StringCollator;
import client.net.sf.saxon.ce.value.AtomicValue;
/**
* A comparer for comparing two atomic values where (a) equals is defined, and is implemented
* using the Java equals() method, and (b) ordering is not defined, and results in a dynamic error.
*/
public class EqualityComparer implements AtomicComparer {
public static EqualityComparer THE_INSTANCE = new EqualityComparer();
/**
* Get the singleton instance of this class
* @return the singleton instance of this class
*/
public static EqualityComparer getInstance() {
return THE_INSTANCE;
}
private EqualityComparer() {}
public StringCollator getCollator() {
return null;
}
/**
* Supply the dynamic context in case this is needed for the comparison
* @param context the dynamic evaluation context
* @return either the original AtomicComparer, or a new AtomicComparer in which the context
* is known. The original AtomicComparer is not modified
*/
public AtomicComparer provideContext(XPathContext context) {
return this;
}
/**
* Compare two AtomicValue objects according to the rules for their data type. UntypedAtomic
* values are compared as if they were strings; if different semantics are wanted, the conversion
* must be done by the caller.
*
* @param a the first object to be compared. It is intended that this should be an instance
* of AtomicValue, though this restriction is not enforced. If it is a StringValue, the
* collator is used to compare the values, otherwise the value must implement the java.util.Comparable
* interface.
* @param b the second object to be compared. This must be comparable with the first object: for
* example, if one is a string, they must both be strings.
* @return <0 if a<b, 0 if a=b, >0 if a>b
* @throws ClassCastException if the objects are not comparable
*/
public int compareAtomicValues(AtomicValue a, AtomicValue b) {
throw new ClassCastException("Values are not comparable");
}
/**
* Compare two AtomicValue objects for equality according to the rules for their data type. UntypedAtomic
* values are compared by converting to the type of the other operand.
* @param a the first object to be compared. This must be an AtomicValue and it must implement
* equals() with context-free XPath comparison semantics
* @param b the second object to be compared. This must be an AtomicValue and it must implement
* equals() with context-free XPath comparison semantics
* @return true if the values are equal, false if not
* @throws ClassCastException if the objects are not comparable
*/
public boolean comparesEqual(AtomicValue a, AtomicValue b) {
return a.equals(b);
}
/**
* Get a comparison key for an object. This must satisfy the rule that if two objects are equal,
* then their comparison keys are equal, and vice versa. There is no requirement that the
* comparison keys should reflect the ordering of the underlying objects.
*/
public ComparisonKey getComparisonKey(AtomicValue a) {
return new ComparisonKey(a.getPrimitiveType().getFingerprint(), a);
}
}
// 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.