com.saxonica.extfn
Class NamespaceSpecificFunctionLibrary

java.lang.Object
  com.saxonica.extfn.NamespaceSpecificFunctionLibrary

All Implemented Interfaces:

Serializable, FunctionLibrary

public class NamespaceSpecificFunctionLibrary
extends Object
implements FunctionLibrary

This class is a function library that binds extension functions whose namespace URI uses a recognized URI scheme such as "java" or "clitype". It delegates the binding of a function name to one of these libraries, based on the URI scheme name. This function library also allows specific URIs to be associated with one of the target function libraries, regardless of their URI scheme.

See Also:

Serialized Form

Constructor Summary

NamespaceSpecificFunctionLibrary(String namespace, FunctionLibrary targetLibrary)

Method Summary

Expression	bind(StructuredQName functionName, Expression[] staticArgs, StaticContext env) Bind a function, given the URI and local parts of the function name, and the list of expressions supplied as arguments.
FunctionLibrary	copy() This method creates a copy of a FunctionLibrary: if the original FunctionLibrary allows new functions to be added, then additions to this copy will not affect the original, or vice versa.
SequenceType[]	getFunctionSignature(StructuredQName functionName, int arity) Test whether a function with a given name and arity is available; if so, return its signature.

Methods inherited from class java.lang.Object

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

Constructor Detail

NamespaceSpecificFunctionLibrary

public NamespaceSpecificFunctionLibrary(String namespace,
                                        FunctionLibrary targetLibrary)

Method Detail

getFunctionSignature

public SequenceType[] getFunctionSignature(StructuredQName functionName,
                                           int arity)

Test whether a function with a given name and arity is available; if so, return its signature. This supports the function-available() function in XSLT; it is also used to support higher-order functions introduced in XQuery 1.1.

This method may be called either at compile time or at run time. If the function library is to be used only in an XQuery or free-standing XPath environment, this method may throw an UnsupportedOperationException.

Specified by:

getFunctionSignature in interface FunctionLibrary

Parameters:

functionName - the qualified name of the function being called

arity - The number of arguments. This is set to -1 in the case of the single-argument function-available() function; in this case the method should return a zero-lengh array if there is some function of this name available for calling.

Returns:

if a function of this name and arity is available for calling, then the type signature of the function, as an array of sequence types in which the zeroth entry represents the return type; or a zero-length array if the function exists but the signature is not known; or null if the function does not exist

bind

public Expression bind(StructuredQName functionName,
                       Expression[] staticArgs,
                       StaticContext env)
                throws XPathException

Bind a function, given the URI and local parts of the function name, and the list of expressions supplied as arguments. This method is called at compile time.

Specified by:

bind in interface FunctionLibrary

Parameters:

functionName - the QName of the function being called

staticArgs - The expressions supplied statically in arguments to the function call. The length of this array represents the arity of the function. The intention is that the static type of the arguments (obtainable via getItemType() and getCardinality()) may be used as part of the binding algorithm. In some cases it may be possible for the function to be pre-evaluated at compile time, for example if these expressions are all constant values.

The conventions of the XPath language demand that the results of a function depend only on the values of the expressions supplied as arguments, and not on the form of those expressions. For example, the result of f(4) is expected to be the same as f(2+2). The actual expression is supplied here to enable the binding mechanism to select the most efficient possible implementation (including compile-time pre-evaluation where appropriate).

env - The static context of the function call

Returns:

An object representing the function to be called, if one is found; null if no function was found matching the required name and arity.

Throws:

XPathException - if a function is found with the required name and arity, but the implementation of the function cannot be loaded or used; or if an error occurs while searching for the function.

copy

public FunctionLibrary copy()

This method creates a copy of a FunctionLibrary: if the original FunctionLibrary allows new functions to be added, then additions to this copy will not affect the original, or vice versa.

Specified by:

copy in interface FunctionLibrary

Returns:

a copy of this function library. This must be an instance of the original class.