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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2022 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.expr.*;
import net.sf.saxon.expr.instruct.Block;
import net.sf.saxon.expr.parser.*;
import net.sf.saxon.functions.registry.BuiltInFunctionSet;
import net.sf.saxon.lib.NamespaceConstant;
import net.sf.saxon.om.*;
import net.sf.saxon.str.EmptyUnicodeString;
import net.sf.saxon.str.UnicodeString;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.FunctionItemType;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.SpecificFunctionType;
import net.sf.saxon.value.*;
import java.util.Arrays;
import java.util.Objects;
import java.util.Properties;
/**
* Abstract superclass for calls to functions in the standard function library
*/
public abstract class SystemFunction extends AbstractFunction {
private int arity;
private BuiltInFunctionSet.Entry details;
private RetainedStaticContext retainedStaticContext;
/**
* Make a system function call (one in the standard function namespace).
*
* @param name The local name of the function.
* @param rsc Necessary information about the static context
* @param arguments the arguments to the function call
* @return a FunctionCall that implements this function, if it exists
* @throws IllegalArgumentException if there is no system function with the required name and arity
*/
/*@Nullable*/
public static Expression makeCall(String name, RetainedStaticContext rsc, Expression... arguments) {
SystemFunction f = makeFunction(name, rsc, arguments.length);
Expression expr = f.makeFunctionCall(arguments);
expr.setRetainedStaticContext(rsc);
return expr;
}
/**
* Make a system function item (one in the standard function namespace).
*
* @param name The local name of the function.
* @param rsc Necessary information about the static context
* @param arity the arity of the function
* @return the function item
* @throws IllegalArgumentException if there is no system function with the required name and arity
*/
public static SystemFunction makeFunction(String name, RetainedStaticContext rsc, int arity) {
Objects.requireNonNull(rsc);
SystemFunction fn = rsc.getConfiguration().makeSystemFunction(name, arity);
if (fn == null) {
throw new IllegalArgumentException(name + "#" + arity);
}
fn.setRetainedStaticContext(rsc);
return fn;
}
/**
* Make an expression that either calls this function, or that is equivalent to a call
* on this function
* @param arguments the supplied arguments to the function call
* @return either a function call on this function, or an expression that delivers
* the same result
*/
public Expression makeFunctionCall(Expression... arguments) {
if (arguments.length > getArity() && isSequenceVariadic()) {
if (getArity() != 1) {
throw new UnsupportedOperationException("Not implemented: sequence-variadic function with arity>1");
}
arguments = new Expression[]{new Block(arguments)};
}
Expression e = new SystemFunctionCall(this, arguments);
e.setRetainedStaticContext(getRetainedStaticContext());
return e;
}
/**
* Set the arity of the function
* @param arity the number of arguments
*/
public void setArity(int arity) {
this.arity = arity;
}
@Override
public boolean isSequenceVariadic() {
return (details.properties & BuiltInFunctionSet.SEQV) != 0;
}
/**
* Get an estimate of the net cost of evaluating the function, excluding the cost of evaluating
* its arguments. The result is 0 for very simple functions like position() and exists(), 1 by
* default, and higher values for particularly expensive functions.
* @return the estimated cost
*/
public int getNetCost() {
return 1;
}
/**
* Allow the function to create an optimized call based on the values of the actual arguments
* @param visitor the expression visitor
* @param contextInfo information about the context item
* @param arguments the supplied arguments to the function call. Note: modifying the contents
* of this array should not be attempted, it is likely to have no effect.
* @return either a function call on this function, or an expression that delivers
* the same result, or null indicating that no optimization has taken place
* @throws XPathException if an error is detected
*/
public Expression makeOptimizedFunctionCall (
ExpressionVisitor visitor, ContextItemStaticInfo contextInfo, Expression... arguments)
throws XPathException {
Optimizer opt = visitor.obtainOptimizer();
if (opt.isOptionSet(OptimizerOptions.CONSTANT_FOLDING)) {
return fixArguments(arguments);
} else {
return null;
}
}
/**
* Optimize for constant argument values
* @param arguments the supplied arguments to the function call
* @return either a function call on this function, or an expression that delivers
* the same result, or null indicating that no optimization has taken place
* @throws XPathException if an error is detected
*/
public Expression fixArguments(Expression... arguments) throws XPathException {
// Check if any arguments are known to be empty, with a declared result for that case
for (int i = 0; i < getArity(); i++) {
if (Literal.isEmptySequence(arguments[i]) && resultIfEmpty(i) != null) {
return Literal.makeLiteral(details.resultIfEmpty[i].materialize());
}
}
return null;
}
/**
* Ask if the function always returns a known result when one of the arguments is an empty sequence
* @param arg the argument whose value is an empty sequence (counting from zero)
* @return the value to be returned when this argument is an empty sequence, or null if unknown / not applicable
*/
protected Sequence resultIfEmpty(int arg) {
return details.resultIfEmpty[arg];
}
/**
* Get the static context in which the function operates, for use with functions whose result
* depends on the static context
* @return the retained static context
*/
public RetainedStaticContext getRetainedStaticContext() {
return retainedStaticContext;
}
/**
* Set the static context in which the function operates, for use with functions whose result
* depends on the static context
*
* @param retainedStaticContext the retained static context
*/
public void setRetainedStaticContext(RetainedStaticContext retainedStaticContext) {
this.retainedStaticContext = retainedStaticContext;
}
/**
* Ask whether the result of the function depends on the context item
* @return true if the function depends on the context item
*/
public boolean dependsOnContextItem() {
return (details.properties & (BuiltInFunctionSet.CITEM | BuiltInFunctionSet.CDOC)) != 0;
}
/**
* Set the details of this type of function
*
* @param entry information giving details of the function signature and other function properties
*/
public void setDetails(BuiltInFunctionSet.Entry entry) {
details = entry;
}
/**
* Get the details of the function signature
*
* @return information about the function signature and other function properties
*/
public BuiltInFunctionSet.Entry getDetails() {
return details;
}
/**
* Get the qualified name of the function being called
*
* @return the qualified name
*/
@Override
public StructuredQName getFunctionName() {
return details.name;
}
/**
* Get a description of this function for use in error messages. For named functions, the description
* is the function name (as a lexical QName). For others, it might be, for example, "inline function",
* or "partially-applied ends-with function".
*
* @return a description of the function for use in error messages
*/
@Override
public String getDescription() {
return details.name.getDisplayName();
}
/**
* Get the arity of the function (the number of arguments). Note that a subclass of SystemFunction may
* support a family of functions with different arity, but an instance of the SystemFunction class always has
* a single arity.
* @return the arity of the function
*/
@Override
public int getArity() {
return arity;
}
/**
* Get the roles of the arguments, for the purposes of streaming
*
* @return an array of OperandRole objects, one for each argument
*/
@Override
public OperandRole[] getOperandRoles() {
OperandRole[] roles = new OperandRole[getArity()];
OperandUsage[] usages;
if (isSequenceVariadic()) {
usages = new OperandUsage[getArity()];
Arrays.fill(usages, details.usage[0]);
} else {
usages = details.usage;
}
try {
for (int i = 0; i < usages.length; i++) {
roles[i] = new OperandRole(0, usages[i], getRequiredType(i));
}
} catch (ArrayIndexOutOfBoundsException e) {
e.printStackTrace();
}
return roles;
}
/**
* For a function that returns an integer or a sequence of integers, get
* a lower and upper bound on the values of the integers that may be returned, from
* static analysis. The default implementation returns null, meaning "unknown" or
* "not applicable". Other implementations return an array of two IntegerValue objects,
* representing the lower and upper bounds respectively. The values
* UNBOUNDED_LOWER and UNBOUNDED_UPPER are used by convention to indicate that
* the value may be arbitrarily large. The values MAX_STRING_LENGTH and MAX_SEQUENCE_LENGTH
* are used to indicate values limited by the size of a string or the size of a sequence.
*
* @return the lower and upper bounds of integer values in the result, or null to indicate
* unknown or not applicable.
*/
/*@Nullable*/
public IntegerValue[] getIntegerBounds() {
return null;
}
/**
* Method called during static type checking. This method may be implemented in subclasses so that functions
* can take advantage of knowledge of the types of the arguments that will be supplied.
* @param visitor an expression visitor, providing access to the static context and configuration
* @param contextItemType information about whether the context item is set, and what its type is
* @param arguments the expressions appearing as arguments in the function call
* @throws XPathException if an error is detected
*/
public void supplyTypeInformation (
ExpressionVisitor visitor, ContextItemStaticInfo contextItemType, Expression[] arguments) throws XPathException {
//default: no action
}
/**
* Determine whether two functions are equivalent
*/
@Override
public boolean equals(Object o) {
return (o instanceof SystemFunction) && super.equals(o);
}
@Override
public int hashCode() {
// included explicitly because equals() is overridden: prevents compiler warnings
return super.hashCode();
}
/**
* Return the error code to be used for type errors. This is overridden for functions
* such as exactly-one(), one-or-more(), ...
*
* @return the error code to be used for type errors in the function call. Normally XPTY0004,
* but different codes are used for functions such as exactly-one()
*/
public String getErrorCodeForTypeErrors() {
return "XPTY0004";
}
/**
* Get the required type of the nth argument
*
* @param arg the number of the argument whose type is requested, zero-based
* @return the required type of the argument as defined in the function signature
*/
public SequenceType getRequiredType(int arg) {
if (details == null) {
return SequenceType.ANY_SEQUENCE;
}
return details.argumentTypes[arg];
// this is overridden for concat()
}
/**
* Determine the item type of the value returned by the function
* @return the item type of the result
*/
public ItemType getResultItemType() {
return details.itemType;
}
/**
* Get the item type of the function item
*
* @return the function item's type
*/
@Override
public FunctionItemType getFunctionItemType() {
SequenceType resultType = SequenceType.makeSequenceType(getResultItemType(), details.cardinality);
return new SpecificFunctionType(details.argumentTypes, resultType);
}
/**
* Get the return type, given knowledge of the actual arguments
* @param args the actual arguments supplied
* @return the best available item type that the function will return
*/
public ItemType getResultItemType(Expression[] args) {
if ((details.properties & BuiltInFunctionSet.AS_ARG0) != 0) {
return args[0].getItemType();
} else if ((details.properties & BuiltInFunctionSet.AS_PRIM_ARG0) != 0) {
return args[0].getItemType().getPrimitiveItemType();
} else {
return details.itemType;
}
}
/**
* Get the cardinality, given knowledge of the actual arguments
* @param args the actual arguments supplied
* @return the most precise available cardinality that the function will return
*/
public int getCardinality(Expression[] args) {
int c = details.cardinality;
if (c == BuiltInFunctionSet.OPT && (details.properties & BuiltInFunctionSet.CARD0) != 0 &&
!Cardinality.allowsZero(args[0].getCardinality())) {
return StaticProperty.EXACTLY_ONE;
} else {
return c;
}
}
/**
* Determine the special properties of this function. The general rule
* is that a system function call is non-creative unless more details
* are defined in a subclass.
* @param arguments the actual arguments supplied in a call to the function
* @return the properties
*/
public int getSpecialProperties(Expression[] arguments) {
if ((details.properties & BuiltInFunctionSet.NEW) != 0) {
return StaticProperty.ALL_NODES_NEWLY_CREATED;
}
int p = StaticProperty.NO_NODES_NEWLY_CREATED;
if ((details.properties & BuiltInFunctionSet.SIDE) != 0) {
p |= StaticProperty.HAS_SIDE_EFFECTS;
}
return p;
}
/**
* Helper method for subclasses: get the context item if it is a node, throwing appropriate errors
* if not
*
* @param context the XPath dynamic context
* @return the context item if it exists and is a node
* @throws XPathException if there is no context item or if the context item is not a node
*/
protected NodeInfo getContextNode(XPathContext context) throws XPathException {
Item item = context.getContextItem();
if (item == null) {
XPathException err = new XPathException("Context item for " + getFunctionName() + "() is absent", "XPDY0002");
err.maybeSetContext(context);
throw err;
} else if (!(item instanceof NodeInfo)) {
XPathException err = new XPathException("Context item for " + getFunctionName() + "() is not a node", "XPTY0004");
err.maybeSetContext(context);
throw err;
} else {
return (NodeInfo) item;
}
}
/**
* Make a dynamic call to a supplied argument function (convenience method for use by implementations)
*
* @param f the function
* @param context the XPath dynamic evaluation context
* @param args the actual arguments to be supplied
* @return the result of invoking the function
* @throws XPathException if a dynamic error occurs within the function
*/
public static Sequence dynamicCall(Function f, XPathContext context, Sequence[] args) throws XPathException {
context = f.makeNewContext(context, null);
context.setCurrentOutputUri(null);
if (context instanceof XPathContextMajor) {
((XPathContextMajor) context).setCurrentRegexIterator(null);
}
return f.call(context, args);
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
@Override
public void export(ExpressionPresenter out) throws XPathException {
out.startElement("fnRef");
StructuredQName qName = getFunctionName();
String name = qName.hasURI(NamespaceConstant.FN) ? qName.getLocalPart() : qName.getEQName();
out.emitAttribute("name", name);
out.emitAttribute("arity", getArity() + "");
if ((getDetails().properties & BuiltInFunctionSet.DEPENDS_ON_STATIC_CONTEXT) != 0) {
out.emitRetainedStaticContext(getRetainedStaticContext(), null);
}
out.endElement();
}
/**
* Type-check a call on this function
* @param caller the function call expression calling this function
* @param visitor the expression visitor
* @param contextInfo static context information relating to the call
* @return a type-checked replacement for the supplied function call
* @throws XPathException if an error is detected
*/
public Expression typeCheckCaller(FunctionCall caller, ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)
throws XPathException {
return caller;
}
@Override
public boolean isTrustedResultType() {
return true;
}
public String getStaticBaseUriString() {
return getRetainedStaticContext().getStaticBaseUriString();
}
/**
* Export any context attributes held within the SystemFunction object. The implementation
* will normally make one or more calls on out.emitAttribute(name, value).
* @param out the export destination
*/
public void exportAttributes(ExpressionPresenter out) {}
/**
* Export any implicit arguments held in optimized form within the SystemFunction call
* @param call the system function call (on this function)
* @param out the export destination
* @throws XPathException if a failure occurs (such as an I/O error)
*/
public void exportAdditionalArguments(SystemFunctionCall call, ExpressionPresenter out) throws XPathException {
}
/**
* Import any attributes found in the export file, that is, any attributes output using
* the exportAttributes method
* @param attributes the attributes, as a properties object
* @throws XPathException if errors are found in the SEF file
*/
public void importAttributes(Properties attributes) throws XPathException {}
/**
* Get the (local) name of a class that can be used to generate bytecode for this
* system function
* @return the name of a bytecode generation class, or null if there is no bytecode
* support for this function
*/
public String getCompilerName() {
return null;
}
/**
* Get a name that identifies the class that can be used to evaluate this function
* in streaming mode, that is, supplying one item or event at a time as it is
* delivered by the parser. Special streaming support is generally available in
* Saxon-EE for all system functions that take a sequence as their argument.
* @return a name that identifies a class that supports streamed evaluation of this system
* function, or null if no such class is available. The mapping of names to classes is
* defined in the Saxon-EE class {@code StreamerMap}. In non-streaming Saxon editions
* (HE and PE) the method always returns null.
*/
public String getStreamerName() {
return null;
}
/**
* Provide a short string showing the contents of the item, suitable
* for use in error messages
*
* @return a depiction of the item suitable for use in error messages
*/
@Override
public String toShortString() {
return getFunctionName().getDisplayName() + '#' + getArity();
}
public String toString() {
return getFunctionName().getDisplayName() + '#' + getArity();
}
/**
* Helper method to get an argument value as a UnicodeString, in the case where an empty sequence
* should be treated as a zero-length string
* @param supplied the actual argumetn values supplied
* @return zero-length string if the input was an empty sequence; otherwise the string value of the
* first item in the sequence
* @throws XPathException if the first item in the sequence has no string value (for example, a map)
*/
protected UnicodeString getUniStringArg(Sequence supplied) throws XPathException {
StringValue item = (StringValue)supplied.head();
return item == null ? EmptyUnicodeString.getInstance() : item.getUnicodeStringValue();
}
}