Package net.sf.saxon.query

Class XQueryFunctionLibrary

  • All Implemented Interfaces:
    FunctionLibrary, XQueryFunctionBinder
    public class XQueryFunctionLibrary
extends java.lang.Object
implements FunctionLibrary, XQueryFunctionBinder
    An XQueryFunctionLibrary is a function library containing all the user-defined functions available for use within a particular XQuery module: that is, the functions declared in that module, and the functions imported from other modules. It also contains (transiently during compilation) a list of function calls within the module that have not yet been bound to a specific function declaration.

    • Constructor Detail

      • XQueryFunctionLibrary

        public XQueryFunctionLibrary​(Configuration config)
        Create an XQueryFunctionLibrary
        Parameters:
        config - the Saxon configuration

    • Method Detail

      • getConfiguration

        public Configuration getConfiguration()
        Get the Configuration options
        Returns:
        the Saxon configuration

      • declareFunction

        public void declareFunction​(XQueryFunction function)
                     throws XPathException
        Register a user-defined XQuery function
        Parameters:
        function - the function to be registered
        Throws:
        XPathException - if there is an existing function with the same name and arity

      • getFunctionItem

        public Function getFunctionItem​(SymbolicName.F functionName,
                                StaticContext staticContext)
                         throws XPathException
        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.

        Specified by:
        getFunctionItem in interface FunctionLibrary
        Parameters:
        functionName - the qualified name of the function being called
        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
        Returns:
        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

      • isAvailable

        public boolean isAvailable​(SymbolicName.F functionName)
        Test whether a function with a given name and arity is available

        This supports the function-available() function in XSLT.

        Specified by:
        isAvailable in interface FunctionLibrary
        Parameters:
        functionName - the qualified name of the function being called
        Returns:
        true if a function of this name and arity is available for calling

      • bind

        public Expression bind​(SymbolicName.F functionName,
                       Expression[] arguments,
                       StaticContext env,
                       java.util.List<java.lang.String> reasons)
        Identify a (namespace-prefixed) function appearing in the expression. This method is called by the XQuery parser to resolve function calls found within the query.

        Note that a function call may appear earlier in the query than the definition of the function to which it is bound. Unlike XSLT, we cannot search forwards to find the function definition. Binding of function calls is therefore a two-stage process; at the time the function call is parsed, we simply register it as pending; subsequently at the end of query parsing all the pending function calls are resolved. Another consequence of this is that we cannot tell at the time a function call is parsed whether it is a call to an internal (XSLT or XQuery) function or to an extension function written in Java.

        Specified by:
        bind in interface FunctionLibrary
        Parameters:
        functionName - the QName of the function being called
        arguments - May be null; if present, the length of the array must match the value of arity. 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).

        env - The static context of the function call
        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.
        Returns:
        an Expression representing the function call. This will normally be a FunctionCall, but it may be rewritten as some other expression.

      • getDeclaration

        public XQueryFunction getDeclaration​(StructuredQName functionName,
                                     int staticArgs)
        Get the function declaration corresponding to a given function name and arity
        Specified by:
        getDeclaration in interface XQueryFunctionBinder
        Parameters:
        functionName - the name of the function as a QName
        staticArgs - the number of expressions supplied as arguments in the function call
        Returns:
        the XQueryFunction if there is one, or null if not.

      • getDeclarationByKey

        public XQueryFunction getDeclarationByKey​(SymbolicName functionKey)
        Get the function declaration corresponding to a given function name and arity, supplied in the form "{uri}local/arity"
        Parameters:
        functionKey - a string in the form "{uri}local/arity" identifying the required function
        Returns:
        the XQueryFunction if there is one, or null if not.

      • getFunctionDefinitions

        public java.util.Iterator<XQueryFunction> getFunctionDefinitions()
        Get an iterator over the Functions defined in this module
        Returns:
        an Iterator, whose items are XQueryFunction objects. It returns all function known to this module including those imported from elsewhere; they can be distinguished by their namespace.

      • fixupGlobalFunctions

        protected void fixupGlobalFunctions​(QueryModule env)
                             throws XPathException
        Fixup all references to global functions. This method is called on completion of query parsing. Each XQueryFunction is required to bind all references to that function to the object representing the run-time executable code of the function.

        This method is for internal use.

        Parameters:
        env - the static context for the main query body.
        Throws:
        XPathException - if an error occurs

      • optimizeGlobalFunctions

        protected void optimizeGlobalFunctions​(QueryModule topModule)
                                throws XPathException
        Optimize the body of all global functions. This may involve inlining functions calls
        Parameters:
        topModule - the top level module of the compilation unit whose functions are to be optimized; functions in separately-compiled imported libraries are unaffected.
        Throws:
        XPathException - if an error occurs

      • explainGlobalFunctions

        public void explainGlobalFunctions​(ExpressionPresenter out)
                            throws XPathException
        Output "explain" information about each declared function
        Parameters:
        out - the ExpressionPresenter that renders the output
        Throws:
        XPathException

      • getUserDefinedFunction

        public UserFunction getUserDefinedFunction​(java.lang.String uri,
                                           java.lang.String localName,
                                           int arity)
        Get the function with a given name and arity. This method is provided so that XQuery functions can be called directly from a Java application. Note that there is no type checking or conversion of arguments when this is done: the arguments must be provided in exactly the form that the function signature declares them.
        Parameters:
        uri - the uri of the function name
        localName - the local part of the function name
        arity - the number of arguments.
        Returns:
        the function identified by the URI, local name, and arity; or null if there is no such 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.