net.sf.saxon.expr.sort
Class TextComparer

java.lang.Object
  net.sf.saxon.expr.sort.TextComparer

All Implemented Interfaces:

Serializable, AtomicComparer

public class TextComparer
extends Object
implements AtomicComparer, Serializable

A Comparer used for comparing sort keys when data-type="text". The items to be compared are converted to strings, and the strings are then compared using an underlying collator

Author:

Michael H. Kay

See Also:

Serialized Form

Constructor Summary

TextComparer(AtomicComparer baseComparer)

Method Summary

int	compareAtomicValues(AtomicValue a, AtomicValue b) Compare two Items by converting them to strings and comparing the string values.
boolean	comparesEqual(AtomicValue a, AtomicValue b) Compare two AtomicValue objects for equality according to the rules for their data type.
AtomicComparer	getBaseComparer() Get the underlying comparer (which doesn't do conversion to string)
StringCollator	getCollator() Get the collation used by this AtomicComparer if any
ComparisonKey	getComparisonKey(AtomicValue a) Get a comparison key for an object.
AtomicComparer	provideContext(XPathContext context) Supply the dynamic context in case this is needed for the comparison

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TextComparer

public TextComparer(AtomicComparer baseComparer)

Method Detail

getBaseComparer

public AtomicComparer getBaseComparer()

Get the underlying comparer (which doesn't do conversion to string)

getCollator

public StringCollator getCollator()

Description copied from interface: AtomicComparer

Get the collation used by this AtomicComparer if any

Specified by:

getCollator in interface AtomicComparer

Returns:

the collation used for comparing strings, or null if not applicable

provideContext

public AtomicComparer provideContext(XPathContext context)

Supply the dynamic context in case this is needed for the comparison

Specified by:

provideContext in interface AtomicComparer

Parameters:

context - the dynamic evaluation context

Returns:

either the original AtomicComparer, or a new AtomicComparer in which the context is known. The original AtomicComparer is not modified

Throws:

NoDynamicContextException - if the context is an "early evaluation" (compile-time) context

compareAtomicValues

public int compareAtomicValues(AtomicValue a,
                               AtomicValue b)
                        throws ClassCastException,
                               NoDynamicContextException

Compare two Items by converting them to strings and comparing the string values.

Specified by:

compareAtomicValues in interface AtomicComparer

Parameters:

a - the first Item to be compared.

b - the second Item to be compared.

Returns:

<0 if a0 if a>b

Throws:

ClassCastException - if the objects are not Items, or are items that cannot be convered to strings (e.g. QNames)

NoDynamicContextException - if this comparer required access to dynamic context information, notably the implicit timezone, and this information is not available. In general this happens if a context-dependent comparison is attempted at compile-time, and it signals the compiler to generate code that tries again at run-time.

comparesEqual

public boolean comparesEqual(AtomicValue a,
                             AtomicValue b)
                      throws NoDynamicContextException

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.

Specified by:

comparesEqual in interface AtomicComparer

Parameters:

a - the first object to be compared.

b - the second object to be compared.

Returns:

true if the values are equal, false if not

Throws:

ClassCastException - if the objects are not comparable

NoDynamicContextException

getComparisonKey

public ComparisonKey getComparisonKey(AtomicValue a)
                               throws NoDynamicContextException

Get a comparison key for an object. This must satisfy the rule that if two objects are equal according to the XPath eq operator, then their comparison keys are equal according to the Java equals() method, and vice versa. There is no requirement that the comparison keys should reflect the ordering of the underlying objects.

Specified by:

getComparisonKey in interface AtomicComparer

Throws:

NoDynamicContextException