net.sf.saxon.pattern.GeneralPositionalPattern Maven / Gradle / Ivy
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 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.ExpressionTool;
import net.sf.saxon.expr.parser.ExpressionVisitor;
import net.sf.saxon.expr.parser.Optimizer;
import net.sf.saxon.expr.parser.PromotionOffer;
import net.sf.saxon.functions.Current;
import net.sf.saxon.om.AxisInfo;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.NodeInfo;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.iter.ManualIterator;
import net.sf.saxon.tree.iter.SingletonIterator;
import net.sf.saxon.tree.iter.UnfailingIterator;
import net.sf.saxon.type.ErrorType;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.Type;
import net.sf.saxon.value.NumericValue;
import java.util.Iterator;
/**
* A GeneralPositionalPattern is a pattern of the form A[P] where A is an axis expression using the child axis
* and P is an expression that depends on the position. When this kind of pattern is used for matching streamed nodes,
* it relies on the histogram data of preceding siblings maintained as part of a
* {@link com.saxonica.stream.om.FleetingParentNode}
*
* This class handles cases where the predicate P is arbitrarily complex. Simple comparisons of position() against
* an integer value are handled by the class SimplePositionalPattern.
*/
public class GeneralPositionalPattern extends Pattern {
private NodeTest nodeTest;
private Expression positionExpr;
private boolean usesPosition = true;
/**
* Create a PositionalChildPattern
*/
public GeneralPositionalPattern(NodeTest base, Expression positionExpr) {
this.nodeTest = base;
this.positionExpr = positionExpr;
}
/**
* Get the filter assocated with the pattern
* @return the filter predicate
*/
public Expression getPositionExpr() {
return positionExpr;
}
/**
* Get the base pattern
* @return the base pattern before filtering
*/
public NodeTest getNodeTest() {
return nodeTest;
}
/**
* Simplify the pattern: perform any context-independent optimisations
* @param visitor an expression visitor
*/
public Pattern simplify(ExpressionVisitor visitor) throws XPathException {
positionExpr = visitor.simplify(positionExpr);
return this;
}
/**
* Type-check the pattern, performing any type-dependent optimizations.
* @param visitor an expression visitor
* @param contextItemType the type of the context item at the point where the pattern appears
* @return the optimised Pattern
*/
public Pattern analyze(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
// analyze each component of the pattern
Optimizer opt = visitor.getConfiguration().obtainOptimizer();
ExpressionVisitor.ContextItemType cit = new ExpressionVisitor.ContextItemType(getItemType(), false);
positionExpr = visitor.typeCheck(positionExpr, cit);
positionExpr = ExpressionTool.unsortedIfHomogeneous(opt, positionExpr);
positionExpr = visitor.optimize(positionExpr, cit);
if (Literal.isConstantBoolean(positionExpr, true)) {
return new ItemTypePattern(nodeTest);
} else if (Literal.isConstantBoolean(positionExpr, false)) {
// if a filter is constant false, the pattern doesn't match anything
return new ItemTypePattern(ErrorType.getInstance());
}
if ((positionExpr.getDependencies() & StaticProperty.DEPENDS_ON_POSITION) == 0) {
usesPosition = false;
}
// See if the expression is now known to be non-positional (see bugs 1908, 1992)
if (!FilterExpression.isPositionalFilter(positionExpr, visitor.getConfiguration().getTypeHierarchy())) {
byte axis = AxisInfo.CHILD;
if (nodeTest.getPrimitiveType() == Type.ATTRIBUTE) {
axis = AxisInfo.ATTRIBUTE;
} else if (nodeTest.getPrimitiveType() == Type.NAMESPACE) {
axis = AxisInfo.NAMESPACE;
}
AxisExpression ae = new AxisExpression(axis, nodeTest);
FilterExpression fe = new FilterExpression(ae, positionExpr);
return PatternMaker.fromExpression(fe, visitor.getConfiguration(), true)
.analyze(visitor, contextItemType);
}
return this;
}
/**
* Replace any calls on current() by a variable reference bound to the supplied binding
*/
@Override
public void bindCurrent(Binding binding) {
if (ExpressionTool.callsFunction(positionExpr, Current.FN_CURRENT)) {
replaceCurrent(positionExpr, binding);
}
}
/**
* 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.
*/
public int getDependencies() {
// the only dependency that's interesting is a dependency on local variables
return positionExpr.getDependencies() & StaticProperty.DEPENDS_ON_LOCAL_VARIABLES;
}
/**
* Iterate over the subexpressions within this pattern
*/
/*@NotNull*/
public Iterator iterateSubExpressions() {
return new MonoIterator(positionExpr);
}
/**
* Replace one subexpression by a replacement subexpression
*
* @param original the original subexpression
* @param replacement the replacement subexpression
* @return true if the original subexpression is found
*/
public boolean replaceSubExpression(Expression original, Expression replacement) {
boolean found = false;
if (positionExpr == original) {
positionExpr = replacement;
found = true;
}
return found;
}
/**
* Allocate slots to any variables used within the pattern
* @param slotManager
* @param nextFree the next slot that is free to be allocated @return the next slot that is free to be allocated
*/
public int allocateSlots(SlotManager slotManager, int nextFree) {
return ExpressionTool.allocateSlots(positionExpr, nextFree, slotManager);
}
/**
* Offer promotion for subexpressions within this pattern. The offer will be accepted if the subexpression
* is not dependent on the factors (e.g. the context item) identified in the PromotionOffer.
* By default the offer is not accepted - this is appropriate in the case of simple expressions
* such as constant values and variable references where promotion would give no performance
* advantage. This method is always called at compile time.
*
* Unlike the corresponding method on {@link net.sf.saxon.expr.Expression}, this method does not return anything:
* it can make internal changes to the pattern, but cannot return a different pattern. Only certain
* kinds of promotion are applicable within a pattern: specifically, promotions affecting local
* variable references within the pattern.
*
* @param offer details of the offer, for example the offer to move
* expressions that don't depend on the context to an outer level in
* the containing expression
* @param parent
* @throws net.sf.saxon.trans.XPathException
* if any error is detected
*/
public void promote(PromotionOffer offer, Expression parent) throws XPathException {
Binding[] savedBindingList = offer.bindingList;
positionExpr = positionExpr.promote(offer, parent);
offer.bindingList = savedBindingList;
}
/**
* Determine whether the pattern matches a given item.
*
*
*
*
* @param item the item to be tested
* @return true if the pattern matches, else false
*/
public boolean matches(Item item, XPathContext context) throws XPathException {
return item instanceof NodeInfo && matchesBeneathAnchor((NodeInfo) item, null, context);
}
/**
* Determine whether this pattern matches a given Node within the subtree rooted at a given
* anchor node. This method is used when the pattern is used for streaming.
* @param node The NodeInfo representing the Element or other node to be tested against the Pattern
* @param anchor The anchor node, which must match any AnchorPattern subpattern
* @param context The dynamic context. Only relevant if the pattern
* uses variables, or contains calls on functions such as document() or key().
* @return true if the node matches the Pattern, false otherwise
*/
public boolean matchesBeneathAnchor(NodeInfo node, NodeInfo anchor, XPathContext context) throws XPathException {
return internalMatches(node, anchor, context);
}
/**
* Test whether the pattern matches, but without changing the current() node
*/
private boolean internalMatches(NodeInfo node, NodeInfo anchor, XPathContext context) throws XPathException {
// System.err.println("Matching node type and fingerprint");
if (!nodeTest.matches(node, context)) {
return false;
}
XPathContext c2 = context.newMinorContext();
UnfailingIterator iter = SingletonIterator.makeIterator(node);
iter.next();
c2.setCurrentIterator(iter);
try {
XPathContext c = c2;
if (usesPosition) {
ManualIterator man = new ManualIterator(node, getActualPosition(node, context, Integer.MAX_VALUE));
XPathContext c3 = c2.newMinorContext();
c3.setCurrentIterator(man);
c = c3;
}
Item predicate = positionExpr.evaluateItem(c);
if (predicate instanceof NumericValue) {
NumericValue position = (NumericValue)positionExpr.evaluateItem(context);
if (position.isWholeNumber() && position.compareTo(0) > 0) {
int requiredPos = (int)position.longValue();
return getActualPosition(node, context, requiredPos) == requiredPos;
} else {
return false;
}
} else {
return ExpressionTool.effectiveBooleanValue(predicate);
}
} catch (XPathException e) {
if ("XTDE0640".equals(e.getErrorCodeLocalPart())) {
// Treat circularity error as fatal (test error213)
throw e;
}
XPathException err = new XPathException("An error occurred matching pattern {" + toString() + "}: ", e);
err.setXPathContext(c2);
err.setErrorCodeQName(e.getErrorCodeQName());
err.setLocator(this);
c2.getController().recoverableError(err);
return false;
}
}
private int getActualPosition(NodeInfo node, XPathContext context, int max) throws XPathException {
return context.getConfiguration().getSiblingPosition(node, nodeTest, max);
}
/**
* Determine the types of nodes to which this pattern applies. Used for optimisation.
* For patterns that match nodes of several types, return Node.NODE
*
* @return the type of node matched by this pattern. e.g. Node.ELEMENT or Node.TEXT
*/
public int getNodeKind() {
return nodeTest.getPrimitiveType();
}
/**
* Determine the fingerprint of nodes to which this pattern applies.
* Used for optimisation.
*
* @return the fingerprint of nodes matched by this pattern.
*/
public int getFingerprint() {
return nodeTest.getFingerprint();
}
/**
* Get an ItemType that all the nodes matching this pattern must satisfy
*/
public ItemType getItemType() {
return nodeTest;
}
/**
* Determine whether this pattern is the same as another pattern
* @param other the other object
*/
public boolean equals(Object other) {
if (other instanceof GeneralPositionalPattern) {
GeneralPositionalPattern fp = (GeneralPositionalPattern)other;
return nodeTest.equals(fp.nodeTest) && positionExpr.equals(fp.positionExpr);
} else {
return false;
}
}
/**
* hashcode supporting equals()
*/
public int hashCode() {
return nodeTest.hashCode() ^ positionExpr.hashCode();
}
}
// Copyright (c) 2012 Saxonica Limited