net.sf.saxon.pattern.GeneralNodePattern Maven / Gradle / Ivy
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2015 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.functions.Current;
import net.sf.saxon.om.AxisInfo;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.NodeInfo;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.iter.AxisIterator;
import net.sf.saxon.tree.iter.ManualIterator;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.Type;
import net.sf.saxon.type.TypeHierarchy;
import net.sf.saxon.type.UType;
import java.util.Iterator;
/**
* A GeneralNodePattern represents a pattern which, because of the presence of positional
* predicates or otherwise, can only be evaluated "the hard way", by evaluating the equivalent
* expression with successive ancestors of the tested node as context item.
*/
public final class GeneralNodePattern extends Pattern {
private Expression equivalentExpr = null;
private NodeTest itemType = null;
/**
* Create a GeneralNodePattern
*
* @param expr the "equivalent expression"
* @param itemType a type that all matched nodes must satisfy
*/
public GeneralNodePattern(Expression expr, NodeTest itemType) {
equivalentExpr = expr;
this.itemType = itemType;
}
/**
* 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 new Operand(this, equivalentExpr, OperandRole.SAME_FOCUS_ACTION);
}
/**
* Test whether a pattern is motionless, that is, whether it can be evaluated against a node
* without repositioning the input stream. This is a necessary condition for patterns used
* as the match pattern of a streamed template rule.
*
* @param allowExtensions true if Saxon streamability extensions are allowed
* @return true if the pattern is motionless, that is, if it can be evaluated against a streamed
* node without changing the position in the streamed input file
*/
public boolean isMotionless(boolean allowExtensions) {
return false;
}
/**
* 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 typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) throws XPathException {
equivalentExpr = equivalentExpr.typeCheck(visitor, ContextItemStaticInfo.DEFAULT);
return this;
}
/**
* Perform optimisation of an expression and its subexpressions. This is the third and final
* phase of static optimization.
*
* This method is called after all references to functions and variables have been resolved
* to the declaration of the function or variable, and after all type checking has been done.
*
* @param visitor an expression visitor
* @param contextInfo the static type of "." at the point where this expression is invoked.
* The parameter is set to null if it is known statically that the context item will be undefined.
* If the type of the context item is not known statically, the argument is set to
* {@link Type#ITEM_TYPE}
* @return the original expression, rewritten if appropriate to optimize execution
* @throws XPathException if an error is discovered during this phase
* (typically a type error)
*/
@Override
public Pattern optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
equivalentExpr = equivalentExpr.optimize(visitor, ContextItemStaticInfo.DEFAULT);
// See if the expression is now known to be non-positional
if (equivalentExpr instanceof FilterExpression && !((FilterExpression) equivalentExpr).isFilterIsPositional()) {
try {
return PatternMaker.fromExpression(equivalentExpr, getConfiguration(), true)
.typeCheck(visitor, ContextItemStaticInfo.DEFAULT);
} catch (XPathException err) {
// cannot make pattern from expression - not a problem, just use the original
}
}
return this;
}
/**
* 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() {
return equivalentExpr.getDependencies() & StaticProperty.DEPENDS_ON_LOCAL_VARIABLES;
}
/**
* Iterate over the subexpressions within this pattern
*/
/*@NotNull*/
public Iterator iterateSubExpressions() {
return new MonoIterator(equivalentExpr);
}
/**
* Replace any calls on current() by a variable reference bound to the supplied binding
*/
@Override
public void bindCurrent(LocalBinding binding) {
if (ExpressionTool.callsFunction(equivalentExpr, Current.FN_CURRENT, false)) {
if (equivalentExpr.isCallOn(Current.class)) {
equivalentExpr = new LocalVariableReference(binding);
} else {
replaceCurrent(equivalentExpr, binding);
}
}
}
/**
* Allocate slots to any variables used within the pattern
*
* @param slotManager details of the stack frame
* @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(equivalentExpr, 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 the parent expression in the expression tree
* @throws net.sf.saxon.trans.XPathException if any error is detected
*/
public void promote(PromotionOffer offer, Expression parent) throws XPathException {
Binding[] savedBindingList = offer.bindingList;
equivalentExpr = equivalentExpr.promote(offer);
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 {
TypeHierarchy th = context.getConfiguration().getTypeHierarchy();
if (!itemType.matches(item, th)) {
return false;
}
AxisIterator anc = ((NodeInfo) item).iterateAxis(AxisInfo.ANCESTOR_OR_SELF);
while (true) {
NodeInfo a = anc.next();
if (a == null) {
return false;
}
if (matchesBeneathAnchor((NodeInfo) item, a, context)) {
return true;
}
}
}
/**
* 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 if present must match any AnchorPattern subpattern; may be null
* @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 {
if (!itemType.matchesNode(node)) {
return false;
}
// for a positional pattern, we do it the hard way: test whether the
// node is a member of the nodeset obtained by evaluating the
// equivalent expression
if (anchor == null) {
AxisIterator ancestors = node.iterateAxis(AxisInfo.ANCESTOR_OR_SELF);
while (true) {
NodeInfo ancestor = ancestors.next();
if (ancestor == null) {
return false;
}
if (matchesBeneathAnchor(node, ancestor, context)) {
return true;
}
}
}
// System.err.println("Testing positional pattern against node " + node.generateId());
XPathContext c2 = context.newMinorContext();
ManualIterator iter = new ManualIterator(anchor);
c2.setCurrentIterator(iter);
try {
SequenceIterator nsv = equivalentExpr.iterate(c2);
while (true) {
NodeInfo n = (NodeInfo) nsv.next();
if (n == null) {
return false;
}
if (n.isSameNodeInfo(node)) {
return true;
}
}
} catch (XPathException.Circularity e) {
throw e;
} catch (XPathException e) {
XPathException err = new XPathException("An error occurred matching pattern {" + toString() + "}: ", e);
err.setXPathContext(c2);
err.setErrorCodeQName(e.getErrorCodeQName());
err.setLocation(getLocation());
c2.getController().recoverableError(err);
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 itemType.getUType();
}
/**
* 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 itemType.getFingerprint();
}
/**
* Get a NodeTest that all the nodes matching this pattern must satisfy
*/
public ItemType getItemType() {
return itemType;
}
public Expression getEquivalentExpr() {
return equivalentExpr;
}
/**
* Determine whether this pattern is the same as another pattern
*
* @param other the other object
*/
public boolean equals(Object other) {
if (other instanceof GeneralNodePattern) {
GeneralNodePattern lpp = (GeneralNodePattern) other;
return equivalentExpr.equals(lpp.equivalentExpr);
} else {
return false;
}
}
/**
* hashcode supporting equals()
*/
public int hashCode() {
return 83641 ^ equivalentExpr.hashCode();
}
/**
* Copy a pattern. This makes a deep copy.
*
* @return the copy of the original pattern
*/
/*@NotNull*/
public Pattern copy() {
GeneralNodePattern n = new GeneralNodePattern(equivalentExpr.copy(), itemType);
ExpressionTool.copyLocationInfo(this, n);
return n;
}
public void export(ExpressionPresenter presenter) {
presenter.startElement("p.genNode");
presenter.emitAttribute("type", itemType.toString());
equivalentExpr.export(presenter);
presenter.endElement();
}
}