net.sf.saxon.sort
Class GenericAtomicComparer
java.lang.Object
net.sf.saxon.sort.GenericAtomicComparer
- AtomicComparer, Serializable
public class GenericAtomicComparer
extends java.lang.Object
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.
GenericAtomicComparer
public GenericAtomicComparer(StringCollator collator,
XPathContext conversion)
Create an GenericAtomicComparer
collator
- the collation to be usedconversion
- a context, used when converting untyped atomic values to the target type.
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.
- compareAtomicValues in interface AtomicComparer
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.
- <0 if a <32b, 0 if a = b, >0 if a > b
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.
- comparesEqual in interface AtomicComparer
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.
getComparisonKey
public ComparisonKey getComparisonKey(AtomicValue a)
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.
- getComparisonKey in interface AtomicComparer
getStringCollator
public StringCollator getStringCollator()
Get the underlying string collator
makeAtomicComparer
public static AtomicComparer makeAtomicComparer(BuiltInAtomicType type0,
BuiltInAtomicType type1,
StringCollator collator,
XPathContext context)
Factory method to make a GenericAtomicComparer for values of known types
type0
- primitive type of the first operandtype1
- primitive type of the second operandcollator
- the collation to be used, if any. This is supplied as a NamedCollation object
which encapsulated both the collation URI and the collation itself.context
- the dynamic context
- a GenericAtomicComparer for values of known types
provideContext
public AtomicComparer provideContext(XPathContext context)
Supply the dynamic context in case this is needed for the comparison
- provideContext in interface AtomicComparer
context
- the dynamic evaluation context
- either the original AtomicComparer, or a new AtomicComparer in which the context
is known. The original AtomicComparer is not modified