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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.expr.*;
import net.sf.saxon.expr.elab.Elaborator;
import net.sf.saxon.expr.elab.PullElaborator;
import net.sf.saxon.expr.elab.PullEvaluator;
import net.sf.saxon.expr.parser.RebindingMap;
import net.sf.saxon.expr.sort.GroupIterator;
import net.sf.saxon.om.*;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.BuiltInAtomicType;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.value.AtomicValue;
/**
* Implements the XSLT function current-grouping-key()
*/
public class CurrentGroupingKeyCall extends Expression implements Callable {
/**
* Get the innermost scoping expression of this expression, for expressions that directly
* depend on something in the dynamic context. For example, in the case of a local variable
* reference this is the expression that causes the relevant variable to be bound; for a
* context item expression it is the innermost focus-setting container. For expressions
* that have no intrinsic dependency on the dynamic context, the value returned is null;
* the scoping container for such an expression is the innermost scoping container of its
* operands.
*
* @return the innermost scoping container of this expression
*/
@Override
public Expression getScopingExpression() {
return CurrentGroupCall.findControllingInstruction(this);
}
/**
* Compute the static cardinality of this expression
*
* @return the computed cardinality, as one of the values {@link net.sf.saxon.expr.StaticProperty#ALLOWS_ZERO_OR_ONE},
* {@link net.sf.saxon.expr.StaticProperty#EXACTLY_ONE}, {@link net.sf.saxon.expr.StaticProperty#ALLOWS_ONE_OR_MORE},
* {@link net.sf.saxon.expr.StaticProperty#ALLOWS_ZERO_OR_MORE}
*/
@Override
protected int computeCardinality() {
// Can return an empty sequence in 2.0 mode
return StaticProperty.ALLOWS_ZERO_OR_MORE;
}
/**
* An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
* This method indicates which of these methods is provided directly. The other methods will always be available
* indirectly, using an implementation that relies on one of the other methods.
*
* @return the implementation method, for example {@link #ITERATE_METHOD} or {@link #EVALUATE_METHOD} or
* {@link #PROCESS_METHOD}
*/
@Override
public int getImplementationMethod() {
return ITERATE_METHOD;
}
/**
* Determine the data type of the expression, if possible. All expression return
* sequences, in general; this method determines the type of the items within the
* sequence, assuming that (a) this is known in advance, and (b) it is the same for
* all items in the sequence.
* This method should always return a result, though it may be the best approximation
* that is available at the time.
*
* @return a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER,
* Type.NODE, or Type.ITEM (meaning not known at compile time)
*/
@Override
public ItemType getItemType() {
return BuiltInAtomicType.ANY_ATOMIC;
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*
* @param out the expression presenter used to display the structure
*/
@Override
public void export(ExpressionPresenter out) throws XPathException {
out.startElement("currentGroupingKey");
out.endElement();
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
* @param rebindings variables to be renamed
*/
@Override
public Expression copy(RebindingMap rebindings) {
return new CurrentGroupingKeyCall();
}
/**
* Determine the dependencies
*/
@Override
public int getIntrinsicDependencies() {
return StaticProperty.DEPENDS_ON_CURRENT_GROUP;
}
/**
* Evaluate the expression
*/
/*@NotNull*/
@Override
public SequenceIterator iterate(XPathContext context) throws XPathException {
return makeElaborator().elaborateForPull().iterate(context);
}
/**
* Call the Callable.
*
* @param context the dynamic evaluation context
* @param arguments the values of the arguments, supplied as Sequences.
* Generally it is advisable, if calling iterate() to process a supplied sequence, to
* call it only once; if the value is required more than once, it should first be converted
* to a {@link GroundedValue} by calling the utility method
* SequenceTool.toGroundedValue().
* If the expected value is a single item, the item should be obtained by calling
* Sequence.head(): it cannot be assumed that the item will be passed as an instance of
* {@link Item} or {@link AtomicValue}.
* It is the caller's responsibility to perform any type conversions required
* to convert arguments to the type expected by the callee. An exception is where
* this Callable is explicitly an argument-converting wrapper around the original
* Callable.
* @return the result of the evaluation, in the form of a Sequence. It is the responsibility
* of the callee to ensure that the type of result conforms to the expected result type.
* @throws XPathException if a dynamic error occurs during the evaluation of the expression
*/
@Override
public Sequence call(XPathContext context, Sequence[] arguments) throws XPathException {
return SequenceTool.toLazySequence(iterate(context));
}
/**
* Make an elaborator for this expression
*
* @return an appropriate {@link Elaborator}
*/
@Override
public Elaborator getElaborator() {
return new CurrentGroupingKeyCallElaborator();
}
private static class CurrentGroupingKeyCallElaborator extends PullElaborator {
@Override
public PullEvaluator elaborateForPull() {
CurrentGroupingKeyCall expr = (CurrentGroupingKeyCall) getExpression();
return context -> {
GroupIterator gi = context.getCurrentGroupIterator();
AtomicSequence result = gi == null ? null : gi.getCurrentGroupingKey();
if (result == null) {
XPathException err = new XPathException("There is no current grouping key", "XTDE1071");
err.setLocation(expr.getLocation());
throw err;
}
return result.iterate();
};
}
}
}