net.sf.saxon.pattern.GeneralPositionalPattern 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.om.AxisInfo;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.NodeInfo;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.iter.ManualIterator;
import net.sf.saxon.tree.util.Navigator;
import net.sf.saxon.type.ErrorType;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.Type;
import net.sf.saxon.type.UType;
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.ee.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 GeneralPositionalPattern
*
* @param base the base expression (to be matched independently of position)
* @param positionExpr the positional filter which matches only if the position of the node is correct
*/
public GeneralPositionalPattern(NodeTest base, Expression positionExpr) {
this.nodeTest = base;
this.positionExpr = positionExpr;
}
/**
* 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, positionExpr, OperandRole.FOCUS_CONTROLLED_ACTION);
}
/**
* 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
*
*/
public Pattern simplify() throws XPathException {
positionExpr = positionExpr.simplify();
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 typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) throws XPathException {
// analyze each component of the pattern
ContextItemStaticInfo cit = new ContextItemStaticInfo(getItemType(), false);
positionExpr = positionExpr.typeCheck(visitor, cit);
positionExpr = ExpressionTool.unsortedIfHomogeneous(positionExpr, false);
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 {
ContextItemStaticInfo cit = new ContextItemStaticInfo(getItemType(), false);
positionExpr = positionExpr.optimize(visitor, cit);
if (Literal.isConstantBoolean(positionExpr, true)) {
return new NodeTestPattern(nodeTest);
} else if (Literal.isConstantBoolean(positionExpr, false)) {
// if a filter is constant false, the pattern doesn't match anything
return new NodeTestPattern(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, test mode-0011)
if (!FilterExpression.isPositionalFilter(positionExpr, 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, getConfiguration(), true)
.typeCheck(visitor, contextInfo);
}
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() {
// 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);
}
/**
* Allocate slots to any variables used within the pattern
*
* @param slotManager manages allocation of slots in a 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(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 the parent expression
* @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);
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.matchesNode(node)) {
return false;
}
XPathContext c2 = context.newMinorContext();
ManualIterator iter = new ManualIterator(node);
c2.setCurrentIterator(iter);
try {
XPathContext c = c2;
if (usesPosition) {
ManualIterator man = new ManualIterator(node, getActualPosition(node, 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, requiredPos) == requiredPos;
} else {
return false;
}
} else {
return ExpressionTool.effectiveBooleanValue(predicate);
}
} catch (XPathException.Circularity e) {
throw e;
} 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.setLocation(getLocation());
c2.getController().recoverableError(err);
return false;
}
}
private int getActualPosition(NodeInfo node, int max) throws XPathException {
return Navigator.getSiblingPosition(node, nodeTest, max);
}
/**
* 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 nodeTest.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 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();
}
/**
* Copy a pattern. This makes a deep copy.
*
* @return the copy of the original pattern
*/
/*@NotNull*/
public Pattern copy() {
GeneralPositionalPattern n = new GeneralPositionalPattern(nodeTest.copy(), positionExpr.copy());
ExpressionTool.copyLocationInfo(this, n);
return n;
}
/**
* Get a string representation of the pattern. This will be in a form similar to the
* original pattern text, but not necessarily identical. It is not guaranteed to be
* in legal pattern syntax.
*/
@Override
public String toString() {
return nodeTest.toString() + "[" + positionExpr.toString() + "]";
}
public void export(ExpressionPresenter presenter) {
presenter.startElement("p.genPos");
presenter.emitAttribute("type", nodeTest.toString());
positionExpr.export(presenter);
presenter.endElement();
}
/*
* Optimization
* Note that any replacement by a BooleanExpressionPattern based on the positionExpr
* REQUIRES that the position has been set appropriately in the context for its evaluation.
* This is NOT the case in generalized {@link net.sf.saxon.trans.Mode.getRule()},
* but is under {@link com.saxonica.ee.optim.ModeEE.getRule()}
* This should be checked.
*//*
public Pattern optimizeForName(int i) {
Object o = nodeTest.optimizeForName(i);
if (o == null) {
return null;
} else {
return optimizePosition();
}
}
public Pattern optimizeForType(int i) {
Object o = nodeTest.optimizeForType(i);
if (o == null) {
return null;
} else {
return optimizePosition();
}
}
private Pattern optimizePosition() {
Expression pe = makePosition(positionExpr, nodeTest);
BooleanExpressionPattern p = new BooleanExpressionPattern(pe);
ExpressionTool.copyLocationInfo(this, p);
//p.setPackageData(getPackageData());
return p;
}
public Pattern applyAxis(byte axis) {
Expression pe = makePosition(positionExpr, nodeTest);
FilterExpression filter = new FilterExpression(new AxisExpression(axis, nodeTest), pe);
BooleanExpressionPattern p = new BooleanExpressionPattern(filter);
ExpressionTool.copyLocationInfo(this, p);
//p.setPackageData(getPackageData());
return p;
}
public static Expression makePosition(Expression expr, NodeTest nodeTest) {
Expression n = expr;
RetainedStaticContext rsc = expr.getRetainedStaticContext();
if (expr instanceof Literal) {
GroundedValue value = ((Literal) expr).getValue();
try {
if (value instanceof IntegerValue) {
Expression operands[] = new Expression[1];
operands[0] = new AxisExpression(AxisInfo.PRECEDING_SIBLING, nodeTest);
Expression position = SystemFunction.makeCall("count", rsc, operands);
n = new CompareToIntegerConstant(position, Token.FEQ,
((IntegerValue)value).longValue() - 1);
return n;
}
Expression position = SystemFunction.makeCall("position", rsc);
n = new CompareToIntegerConstant(position, Token.FEQ,
((IntegerValue) ((Literal) expr).getValue()).longValue());
} catch (XPathException e) {
e.printStackTrace();
}
} else if (expr instanceof CompareToIntegerConstant) {
CompareToIntegerConstant c = (CompareToIntegerConstant)expr;
Operand op1 = expr.operands().iterator().next();
Expression e1 = op1.getChildExpression();
if (e1.isCallOn(PositionAndLast.class)) {
Expression position = SystemFunction.makeCall("count",
rsc, new AxisExpression(AxisInfo.PRECEDING_SIBLING, nodeTest));
n = new CompareToIntegerConstant(position, c.getComparisonOperator(),
c.getComparand() - 1);
return n;
}
}
return n;
}*/
}
// Copyright (c) 2012 Saxonica Limited