Package net.sf.saxon.expr.sort

Class GenericAtomicComparer

java.lang.Object

net.sf.saxon.expr.sort.GenericAtomicComparer

All Implemented Interfaces:

AtomicComparer

Direct Known Subclasses:

SwitchCaseComparer

public class GenericAtomicComparer
extends java.lang.Object
implements AtomicComparer

An AtomicComparer used for comparing atomic values of arbitrary item types. It encapsulates a Collator that is used when the values to be compared are strings. It also supports a separate method for testing equality of items, which can be used for data types that are not ordered.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	GenericAtomicComparer.AtomicComparisonFunction	An AtomicComparisonFunction compares two atomic values to return a result of true or false.

Constructor Summary

Constructors

Constructor	Description
GenericAtomicComparer(StringCollator collator, XPathContext conversionContext)	Create an GenericAtomicComparer

Method Summary

Modifier and Type	Method	Description
int	compareAtomicValues(AtomicValue a, AtomicValue b)	Compare two AtomicValue objects according to the rules for their data type.
boolean	comparesEqual(AtomicValue a, AtomicValue b)	Compare two AtomicValue objects for equality according to the rules for their data type.
boolean	equals(java.lang.Object obj)
StringCollator	getCollator()	Get the collation used by this AtomicComparer if any
XPathContext	getContext()
StringCollator	getStringCollator()	Get the underlying string collator
int	hashCode()
static AtomicComparer	makeAtomicComparer(BuiltInAtomicType type0, BuiltInAtomicType type1, StringCollator collator, XPathContext context)	Factory method to make a GenericAtomicComparer for values of known types
static GenericAtomicComparer.AtomicComparisonFunction	makeAtomicComparisonFunction(BuiltInAtomicType type0, BuiltInAtomicType type1, StringCollator collator, int operator, boolean allowRecursion, int version)	Factory method to make a ComparisonFunction for values of known types
GenericAtomicComparer	provideContext(XPathContext context)	Supply the dynamic context in case this is needed for the comparison
java.lang.String	save()	Create a string representation of this AtomicComparer that can be saved in a compiled package and used to reconstitute the AtomicComparer when the package is reloaded

Methods inherited from class java.lang.Object

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

Constructor Detail

GenericAtomicComparer

public GenericAtomicComparer(StringCollator collator,
                             XPathContext conversionContext)

Create an GenericAtomicComparer

Parameters:

collator - the collation to be used

conversionContext - a context, used when converting untyped atomic values to the target type.

Method Detail

makeAtomicComparer

public static AtomicComparer makeAtomicComparer(BuiltInAtomicType type0,
                                                BuiltInAtomicType type1,
                                                StringCollator collator,
                                                XPathContext context)

Factory method to make a GenericAtomicComparer for values of known types

Parameters:

type0 - primitive type of the first operand

type1 - primitive type of the second operand

collator - the collation to be used, if any. This is supplied as a SimpleCollation object which encapsulated both the collation URI and the collation itself.

context - the dynamic context

Returns:

a GenericAtomicComparer for values of known types

makeAtomicComparisonFunction

public static GenericAtomicComparer.AtomicComparisonFunction makeAtomicComparisonFunction(BuiltInAtomicType type0,
                                                                                          BuiltInAtomicType type1,
                                                                                          StringCollator collator,
                                                                                          int operator,
                                                                                          boolean allowRecursion,
                                                                                          int version)

Factory method to make a ComparisonFunction for values of known types

Parameters:

type0 - primitive type of the first operand

type1 - primitive type of the second operand

collator - the collation to be used, if any. This is supplied as a SimpleCollation object which encapsulated both the collation URI and the collation itself.

operator - the comparison operator, fpr example Token.FEQ

allowRecursion - flag to stop infinite recursion (the function recurses if the static types are not known; it then relies on testing the run-time types)

Returns:

a comparison function for two atomic values (neither of which may be null)

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 GenericAtomicComparer 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

getStringCollator

public StringCollator getStringCollator()

Get the underlying string collator

Returns:

the string collator

compareAtomicValues

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

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.

Specified by:

compareAtomicValues in interface AtomicComparer

Parameters:

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.

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.

Returns:

<0 if a < b, 0 if a = b, >0 if a > b

Throws:

java.lang.ClassCastException - if the objects are not comparable

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 as if they were strings; if different semantics are wanted, the conversion must be done by the caller.

Specified by:

comparesEqual in interface AtomicComparer

Parameters:

a - the first object to be compared. If it is a StringValue, the collator is used to compare the values, otherwise the value must implement the equals() method.

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.

Returns:

true if the values are equal, false if not

Throws:

java.lang.ClassCastException - if the objects are not comparable

NoDynamicContextException - if no dynamic context has been supplied, and a dynamic context is needed (for example, because the comparison uses the implicit timezone)

getContext

public XPathContext getContext()

save

public java.lang.String save()

Create a string representation of this AtomicComparer that can be saved in a compiled package and used to reconstitute the AtomicComparer when the package is reloaded

Specified by:

save in interface AtomicComparer

Returns:

a string representation of the AtomicComparer

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object