package client.net.sf.saxon.ce.expr.sort;
import client.net.sf.saxon.ce.expr.XPathContext;
import client.net.sf.saxon.ce.lib.NamespaceConstant;
import client.net.sf.saxon.ce.lib.StringCollator;
import client.net.sf.saxon.ce.om.StandardNames;
import client.net.sf.saxon.ce.value.AtomicValue;
/**
* An AtomicComparer used for comparing strings, untypedAtomic values, and URIs using a collation.
* A CollatingAtomicComparer is used when it is known in advance that both operands will be of these
* types. This enables all conversions and promotions to be bypassed: the string values of both operands
* are simply extracted and passed to the collator for comparison.
*
* @author Michael H. Kay
*
*/
public class CollatingAtomicComparer implements AtomicComparer {
private StringCollator collator;
private String collationURI;
private boolean canReturnCollationKeys;
/**
* Create an GenericAtomicComparer
* @param collator the collation to be used. If the method is called at compile time, this should
* be a NamedCollation so that it can be cloned at run-time.
*/
public CollatingAtomicComparer(StringCollator collator) {
if (collator == null) {
this.collator = CodepointCollator.getInstance();
collationURI = NamespaceConstant.CODEPOINT_COLLATION_URI;
} else {
this.collator = collator;
collationURI = "*unknown*";
}
canReturnCollationKeys = false;
}
public StringCollator getCollator() {
return collator;
}
/**
* 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;
}
/**
* Get the collation URI
* @return the collation URI
*/
public String getCollationURI() {
return collationURI;
}
/**
* 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) {
if (a == null) {
if (b == null) {
return 0;
} else {
return -1;
}
} else if (b == null) {
return +1;
}
return collator.compareStrings(a.getStringValue(), b.getStringValue());
}
/**
* 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. 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 equals() method.
* @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 boolean comparesEqual(AtomicValue a, AtomicValue b) {
return compareAtomicValues(a, b) == 0;
}
/**
* 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) {
if (canReturnCollationKeys) {
return new ComparisonKey(StandardNames.XS_STRING, collator.getCollationKey(a.getStringValue()));
} else {
return new ComparisonKey(StandardNames.XS_STRING, a.getStringValue());
}
}
}
// 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.