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 "ordinary" atomic values, where the values implement the Comparable
* interface and the equals() method with the appropriate XPath semantics. This rules out use of
* collations, conversion of untyped atomic values, and context dependencies such as implicit timezone.
*/
public class ComparableAtomicValueComparer implements AtomicComparer {
private static ComparableAtomicValueComparer THE_INSTANCE = new ComparableAtomicValueComparer();
/**
* Get the singleton instance of this class
* @return the singleton instance of this class
*/
public static ComparableAtomicValueComparer getInstance() {
return THE_INSTANCE;
}
protected ComparableAtomicValueComparer() {}
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. This must be an AtomicValue and it must implement
* Comparable with context-free XPath comparison semantics
* @param b the second object to be compared. This must be an AtomicValue and it must implement
* Comparable with context-free XPath comparison semantics
* @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) {
if (a == null) {
return (b == null ? 0 : -1);
} else if (b == null) {
return +1;
}
return ((Comparable)a).compareTo(b);
}
/**
* 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.