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The XSLT and XQuery Processor
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2023 Saxonica Limited
// 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.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.functions;
import net.sf.saxon.Configuration;
import net.sf.saxon.expr.Expression;
import net.sf.saxon.expr.StaticContext;
import net.sf.saxon.om.FunctionItem;
import net.sf.saxon.om.StructuredQName;
import net.sf.saxon.trans.SymbolicName;
import net.sf.saxon.trans.XPathException;
import java.util.List;
import java.util.Map;
/**
* A FunctionLibrary handles the binding of function calls in XPath (or XQuery) expressions.
* There are a number of implementations of this
* class to handle different kinds of function: system functions, constructor functions, vendor-defined
* functions, Java extension functions, stylesheet functions, and so on. There is also an implementation
* {@link net.sf.saxon.functions.FunctionLibraryList} that allows a FunctionLibrary
* to be constructed by combining other FunctionLibrary objects.
*/
public interface FunctionLibrary {
default void setConfiguration(Configuration config) {}
/**
* Test whether a function with a given name and arity is available
* This supports the function-available() function in XSLT.
*
* @param functionName the qualified name of the function being called, together with its arity.
* For legacy reasons, the arity may be set to -1 to mean any arity will do
* @param languageLevel the XPath language level (times 10, e.g. 31 for XPath 3.1)
* @return true if a function of this name and arity is available for calling
*/
/*@Nullable*/
boolean isAvailable(SymbolicName.F functionName, int languageLevel);
/**
* 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.
*
* @param functionName the QName of the function being called
* @param staticArgs Contains the expressions supplied statically in arguments to the function call.
* 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).
* @param keywords May be null if no keywords are used in the function call. Otherwise, a map identifying the
* keywords appearing in the function call, and the 0-based position at which they appeared.
* @param env The static context of the function call
* @param reasons If no matching function is found by the function library, it may add
* a diagnostic explanation to this list explaining why none of the available
* functions could be used.
* @return An expression equivalent to a call on the specified function, if one is found;
* null if no function was found matching the required name and arity.
* @throws XPathException if a matching function was identified, but the call is incorrect,
* for example because it uses incorrect argument keywords
*/
/*@Nullable*/
Expression bind(SymbolicName.F functionName, Expression[] staticArgs,
Map keywords, StaticContext env, List reasons) throws XPathException;
/**
* 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.
*
* @return a copy of this function library. This must be an instance of the original class.
*/
FunctionLibrary copy();
/**
* Test whether a function with a given name and arity is available; if so, return a function
* item that can be dynamically called.
* This supports the function-lookup() function in XPath 3.0.
*
* @param functionName the qualified name of the function being called
* @param staticContext the static context to be used by the function, in the event that
* it is a system function with dependencies on the static context
* @return if a function of this name and arity is available for calling, then a corresponding
* function item; or null if the function does not exist
* @throws XPathException in the event of certain errors, for example attempting to get a function
* that is private
*/
/*@Nullable*/
FunctionItem getFunctionItem(SymbolicName.F functionName, StaticContext staticContext)
throws XPathException;
}