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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.pattern;
import net.sf.saxon.expr.*;
import net.sf.saxon.expr.instruct.SlotManager;
import net.sf.saxon.expr.parser.*;
import net.sf.saxon.om.*;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.UncheckedXPathException;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.iter.ManualIterator;
import net.sf.saxon.type.AlphaCode;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.UType;
import net.sf.saxon.value.SequenceType;
/**
* A NodeSetPattern is a pattern based on an expression that is evaluated to return a set of nodes;
* a node matches the pattern if it is a member of this node-set.
* In XSLT 2.0 there are two forms of NodeSetPattern allowed, represented by calls on the id() and
* key() functions. In XSLT 3.0, additional forms are allowed, for example a variable reference, and
* a call to the doc() function. This class provides the general capability to use any expression
* at the head of a pattern. This is used also to support streaming, where streaming XPath expressions
* are mapped to patterns.
*/
public class NodeSetPattern extends Pattern {
private final Operand selectionOp;
private ItemType itemType;
/**
* Create a node-set pattern.
*
* @param exp an expression that can be evaluated to return a node-set; a node matches the pattern
* if it is present in this node-set. The expression must not depend on the focus, though it can depend on
* other aspects of the dynamic context such as local or global variables.
*/
public NodeSetPattern(Expression exp) {
selectionOp = new Operand(this, exp, OperandRole.NAVIGATE);
}
/**
* Get the immediate sub-expressions of this expression, with information about the relationship
* of each expression to its parent expression. Default implementation
* works off the results of iterateSubExpressions()
* If the expression is a Callable, then it is required that the order of the operands
* returned by this function is the same as the order of arguments supplied to the corresponding
* call() method.
*
* @return an iterator containing the sub-expressions of this expression
*/
@Override
public Iterable operands() {
return selectionOp;
}
/**
* Get the underlying expression
* @return the expression that returns all the selected nodes
*/
public Expression getSelectionExpression() {
return selectionOp.getChildExpression();
}
/**
* Type-check the pattern.
* Default implementation does nothing. This is only needed for patterns that contain
* variable references or function calls.
*
* @return the optimised Pattern
*/
@Override
public Pattern typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) throws XPathException {
selectionOp.setChildExpression(getSelectionExpression().typeCheck(visitor, contextItemType));
RoleDiagnostic role = new RoleDiagnostic(RoleDiagnostic.MATCH_PATTERN, getSelectionExpression().toString(), 0);
TypeChecker tc = visitor.getConfiguration().getTypeChecker(false);
Expression checked = getSelectionExpression();
try {
checked = tc.staticTypeCheck(
getSelectionExpression(), SequenceType.NODE_SEQUENCE, role, visitor);
} catch (XPathException e) {
visitor.issueWarning("Pattern will never match anything. " + e.getMessage(), getLocation());
checked = Literal.makeEmptySequence();
}
selectionOp.setChildExpression(checked);
itemType = getSelectionExpression().getItemType();
return this;
}
@Override
public Pattern optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
visitor.obtainOptimizer().optimizeNodeSetPattern(this);
return this;
}
/**
* Set the item type, that is, the type of nodes/items which the pattern will match
* @param type the item type that the pattern will match
*/
public void setItemType(ItemType type) {
this.itemType = type;
}
/**
* Get the dependencies of the pattern. The only possible dependency for a pattern is
* on local variables. This is analyzed in those patterns where local variables may appear.
*/
@Override
public int getDependencies() {
return getSelectionExpression().getDependencies();
}
/**
* Allocate slots to any variables used within the pattern
*
* @param slotManager the slot manager representing the stack frame for local variables
* @param nextFree the next slot that is free to be allocated @return the next slot that is free to be allocated
*/
@Override
public int allocateSlots(SlotManager slotManager, int nextFree) {
return ExpressionTool.allocateSlots(getSelectionExpression(), nextFree, slotManager);
}
/**
* Select nodes in a document using this PatternFinder.
*
* @param doc the document node at the root of a tree
* @param context the dynamic evaluation context
* @return an iterator over the selected nodes in the document.
*/
@Override
public SequenceIterator selectNodes(TreeInfo doc, XPathContext context) throws XPathException {
XPathContext c2 = context.newMinorContext();
ManualIterator mi = new ManualIterator(doc.getRootNode());
c2.setCurrentIterator(mi);
return getSelectionExpression().iterate(c2);
}
/**
* Determine whether this Pattern matches the given Node
*
* @param item The NodeInfo representing the Element or other node to be tested against the Pattern
* @return true if the node matches the Pattern, false otherwise
*/
@Override
public boolean matches(Item item, XPathContext context) throws XPathException {
if (item instanceof NodeInfo) {
try {
Expression exp = getSelectionExpression();
if (exp instanceof GlobalVariableReference) {
GroundedValue value = ((GlobalVariableReference)exp).evaluateVariable(context);
return value.containsNode((NodeInfo)item);
} else {
SequenceIterator iter = exp.iterate(context);
return SingletonIntersectExpression.containsNode(iter, (NodeInfo) item);
}
} catch (XPathException.Circularity | XPathException.StackOverflow e) {
throw e;
} catch (XPathException | UncheckedXPathException e) {
// treat pattern matching errors as a non-match
return false;
}
} else {
return false;
}
}
/**
* Get a UType indicating which kinds of items this Pattern can match.
*
* @return a UType indicating all the primitive types of item that the pattern can match.
*/
@Override
public UType getUType() {
return getItemType().getUType();
}
/**
* Get a NodeTest that all the nodes matching this pattern must satisfy
*/
@Override
public ItemType getItemType() {
if (itemType == null) {
itemType = getSelectionExpression().getItemType();
}
if (itemType instanceof NodeTest) {
return itemType;
} else {
return AnyNodeTest.getInstance();
}
}
/**
* Determine whether this pattern is the same as another pattern
*
* @param other the other object
*/
public boolean equals(Object other) {
return (other instanceof NodeSetPattern) &&
((NodeSetPattern) other).getSelectionExpression().isEqual(getSelectionExpression());
}
/**
* Hashcode supporting equals()
*/
@Override
protected int computeHashCode() {
return 0x73108728 ^ getSelectionExpression().hashCode();
}
/**
* Copy a pattern. This makes a deep copy.
*
* @return the copy of the original pattern
* @param rebindings variable bindings to be changed if encountered
*/
/*@NotNull*/
@Override
public Pattern copy(RebindingMap rebindings) {
NodeSetPattern n = new NodeSetPattern(getSelectionExpression().copy(rebindings));
ExpressionTool.copyLocationInfo(this, n);
n.setOriginalText(getOriginalText());
return n;
}
@Override
public void export(ExpressionPresenter presenter) throws XPathException {
presenter.startElement("p.nodeSet");
if (itemType != null) {
presenter.emitAttribute("test", AlphaCode.fromItemType(itemType));
}
getSelectionExpression().export(presenter);
presenter.endElement();
}
}