net.sf.saxon.pattern.Pattern 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.Configuration;
import net.sf.saxon.expr.*;
import net.sf.saxon.expr.instruct.SlotManager;
import net.sf.saxon.expr.parser.ContextItemStaticInfo;
import net.sf.saxon.expr.parser.ExpressionVisitor;
import net.sf.saxon.expr.parser.PromotionOffer;
import net.sf.saxon.expr.parser.XPathParser;
import net.sf.saxon.functions.Current;
import net.sf.saxon.om.*;
import net.sf.saxon.style.ExpressionContext;
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.EmptyIterator;
import net.sf.saxon.tree.iter.PrependIterator;
import net.sf.saxon.tree.iter.SingletonIterator;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.UType;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
/**
* A Pattern represents the result of parsing an XSLT pattern string.
* Patterns are created by calling the static method Pattern.make(string).
* The pattern is used to test a particular node by calling match().
*/
public abstract class Pattern extends PseudoExpression {
private double priority = 0.5;
/**
* Static factory method to make a Pattern by parsing a String.
*
* @param pattern The pattern text as a String
* @param env An object defining the compile-time context for the expression
* @param packageData The package containing this pattern
* @return The pattern object
* @throws net.sf.saxon.trans.XPathException if the pattern is invalid
*/
public static Pattern make(String pattern, StaticContext env, PackageData packageData) throws XPathException {
int languageLevel = 20;
if (packageData.getXPathVersion() >= 30 && env.getXPathVersion() >= 30) {
languageLevel = 30;
}
int lineNumber = env instanceof ExpressionContext ? ((ExpressionContext) env).getStyleElement().getLineNumber() : -1;
PatternParser parser = (PatternParser) env.getConfiguration().newExpressionParser("PATTERN", false, languageLevel);
((XPathParser) parser).setLanguage(XPathParser.XSLT_PATTERN, env.getXPathVersion());
Pattern pat = parser.parsePattern(pattern, env, lineNumber);
pat.setRetainedStaticContext(env.makeRetainedStaticContext());
// System.err.println("Simplified [" + pattern + "] to " + pat.getClass() + " default prio = " + pat.getDefaultPriority());
// set the pattern text for use in diagnostics
pat.setOriginalText(pattern);
pat = pat.simplify();
return pat;
}
/**
* Replace any call to current() within a contained expression by a reference to a variable
* @param exp the expression in which the replacement is to take place (which must not itself be
* a call to current())
* @param binding the binding for the variable reference
*/
protected static void replaceCurrent(Expression exp, LocalBinding binding) {
for (Operand o : exp.operands()) {
Expression child = o.getChildExpression();
if (child.isCallOn(Current.class)) {
LocalVariableReference ref = new LocalVariableReference(binding);
o.setChildExpression(ref);
} else {
replaceCurrent(child, binding);
}
}
}
/**
* Replace any calls on current() by a variable reference bound to the supplied binding
*/
public void bindCurrent(LocalBinding binding) {
// default: no action
}
/**
* Set the original text of the pattern for use in diagnostics
*
* @param text the original text of the pattern
*/
public void setOriginalText(String text) {
/*originalText = text;*/
}
/**
* Simplify the pattern by applying any context-independent optimisations.
* Default implementation does nothing.
*
*/
public Pattern simplify() throws XPathException {
return this;
}
/**
* Type-check the pattern.
*
* @param visitor the expression visitor
* @param contextInfo the type of the context item at the point where the pattern
* is defined. Set to null if it is known that the context item is undefined.
* @return the optimised Pattern
*/
public Pattern typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
typeCheckChildren(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.
*
* @return the dependencies, as a bit-significant mask
*/
public int getDependencies() {
return 0;
}
/**
* Iterate over the subexpressions within this pattern
*
* @return an iterator over the subexpressions. Default implementation returns an empty sequence
*/
/*@NotNull*/
public Iterator iterateSubExpressions() {
List list = Collections.emptyList();
return list.iterator();
}
/**
* Set the static context for use in evaluating subexpressions
* @param rsc the static context
*/
//
// public void setRetainedStaticContext(RetainedStaticContext rsc) {
// for (Iterator iter = iterateSubExpressions(); iter.hasNext();) {
// Expression exp = iter.next();
// exp.setRetainedStaticContext(rsc);
// }
// }
/**
* 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
*/
public int allocateSlots(SlotManager slotManager, int nextFree) {
return nextFree;
}
/**
* 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 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 {
// default implementation does nothing
}
/**
* 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 if false, the result is determined strictly according to the W3C
* "guaranteed streamability rules. If true, Saxon extensions are permitted: that is, constructs
* may be recognized as motionless by Saxon even if they are not recognized as motionless by
* the W3C rules.
* @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) {
// default implementation for subclasses
return true;
}
/**
* Evaluate a pattern as a boolean expression, returning true if the context item matches the pattern
* @param context the evaluation context
* @return true if the context item matches the pattern
* @throws XPathException if an error occurs during pattern matching
*/
public final boolean effectiveBooleanValue(XPathContext context) throws XPathException {
return matches(context.getContextItem(), context);
}
/**
* Determine whether this Pattern matches the given item. This is the main external interface
* for matching patterns: it sets current() to the node being tested
*
* @param item The item to be tested against the Pattern
* @param context The dynamic context.
* @return true if the node matches the Pattern, false otherwise
* @throws XPathException if an error occurs while matching the pattern (the caller will usually
* treat this the same as a false result)
*/
public abstract boolean matches(Item item, XPathContext context) throws XPathException;
/**
* 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
* @throws XPathException if an error occurs while matching the pattern (the caller will usually
* treat this the same as a false result)
*/
public boolean matchesBeneathAnchor(NodeInfo node, NodeInfo anchor, XPathContext context) throws XPathException {
// default implementation ignores the anchor node
return matches(node, context);
}
/**
* Select nodes in a document using this PatternFinder.
*
* @param document the document
* @param context the dynamic evaluation context
* @return an iterator over the selected nodes in the document.
*/
public SequenceIterator selectNodes(TreeInfo document, final XPathContext context) throws XPathException {
NodeInfo doc = document.getRootNode();
final UType uType = getUType();
if (UType.DOCUMENT.subsumes(uType)) {
if (matches(doc, context)) {
return SingletonIterator.makeIterator(doc);
} else {
return EmptyIterator.getInstance();
}
} else if (UType.ATTRIBUTE.subsumes(uType)) {
AxisIterator allElements = doc.iterateAxis(AxisInfo.DESCENDANT, NodeKindTest.ELEMENT);
MappingFunction atts = new MappingFunction() {
public SequenceIterator map(NodeInfo item) {
return item.iterateAxis(AxisInfo.ATTRIBUTE);
}
};
SequenceIterator allAttributes =
new MappingIterator(allElements, atts);
ItemMappingFunction test = new ItemMappingFunction() {
public NodeInfo mapItem(NodeInfo item) throws XPathException {
if (matches(item, context)) {
return item;
} else {
return null;
}
}
};
return new ItemMappingIterator(allAttributes, test);
} else if (UType.NAMESPACE.subsumes(uType)) {
AxisIterator allElements = doc.iterateAxis(AxisInfo.DESCENDANT, NodeKindTest.ELEMENT);
MappingFunction atts = new MappingFunction() {
public SequenceIterator map(NodeInfo item) {
return item.iterateAxis(AxisInfo.NAMESPACE);
}
};
SequenceIterator allNamespaces =
new MappingIterator(allElements, atts);
ItemMappingFunction test = new ItemMappingFunction() {
public NodeInfo mapItem(NodeInfo item) throws XPathException {
if (matches(item, context)) {
return item;
} else {
return null;
}
}
};
return new ItemMappingIterator(allNamespaces, test);
} else if (UType.CHILD_NODE_KINDS.subsumes(uType)) {
AxisIterator allChildren = doc.iterateAxis(AxisInfo.DESCENDANT, new MultipleNodeKindTest(uType));
ItemMappingFunction test = new ItemMappingFunction() {
public Item mapItem(Item item) throws XPathException {
if (matches(item, context)) {
return item;
} else {
return null;
}
}
};
return new ItemMappingIterator(allChildren, test);
} else {
// TODO: handle patterns that match namespaces as well as other nodes
AxisIterator allChildren = doc.iterateAxis(AxisInfo.DESCENDANT);
MappingFunction attsOrSelf = new MappingFunction() {
public SequenceIterator map(NodeInfo item) {
return new PrependIterator(item, item.iterateAxis(AxisInfo.ATTRIBUTE));
}
};
SequenceIterator attributesOrSelf =
new MappingIterator(allChildren, attsOrSelf);
ItemMappingFunction test = new ItemMappingFunction() {
public Item mapItem(Item item) throws XPathException {
if (matches(item, context)) {
return item;
} else {
return null;
}
}
};
return new ItemMappingIterator(attributesOrSelf, test);
}
}
/**
* 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.
*/
public abstract UType getUType();
/**
* Determine the name fingerprint of nodes to which this pattern applies. Used for
* optimisation.
*
* @return A fingerprint that the nodes must match, or -1 if it can match multiple fingerprints,
* or it if matches atomic values
*/
public int getFingerprint() {
return -1;
}
/**
* Get an ItemType that all the items matching this pattern must satisfy
*
* @return an ItemType, as specific as possible, which all the matching items satisfy
*/
public abstract ItemType getItemType();
/**
* Set a priority to override the default priority. This is used when the pattern is written in a complex
* form such as a[true()] justifying a priority of 0.5, but then simplifies down to an NodeTestPattern
*
* @param priority the priority to be used if no explicit priority is given in the template rule
*/
public void setPriority(double priority) {
this.priority = priority;
}
/**
* Determine the default priority to use if this pattern appears as a match pattern
* for a template with no explicit priority attribute.
*
* @return the default priority for the pattern
*/
public double getDefaultPriority() {
return priority;
}
/**
* 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.
*/
public String toString() {
return "pattern matching " + getItemType().toString();
}
/**
* Get the host language (XSLT, XQuery, XPath) used to implement the code in this container
*
* @return typically {@link net.sf.saxon.Configuration#XSLT} or {@link net.sf.saxon.Configuration#XQUERY}
*/
public int getHostLanguage() {
return Configuration.XSLT;
}
/**
* Convert the pattern to a typed pattern, in which an element name is treated as
* schema-element(N)
*
* @param val either "strict" or "lax" depending on the value of xsl:mode/@typed
* @return either the original pattern unchanged, or a new pattern as the result of the
* conversion
* @throws XPathException if the pattern cannot be converted
*/
public Pattern convertToTypedPattern(String val) throws XPathException {
return null;
}
public abstract void export(ExpressionPresenter presenter);
// /**
// * Copy location information (the line number, priority and references to package) from one pattern
// * to another
// *
// * @param from the pattern containing the location information
// * @param to the pattern to which the information is to be copied
// */
// public static void copyLocationInfo(Pattern from, Pattern to) {
// if (from != null && to != null) {
// to.setSystemId(from.getSystemId());
// to.setLineNumber(from.getLineNumber());
// to.setPackageData(from.getPackageData());
// to.setOriginalText(from.getOriginalText());
// to.setPriority(from.getDefaultPriority());
// }
// }
public abstract Pattern copy();
/**
* 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 net.sf.saxon.type.Type#ITEM_TYPE}
* @return the original expression, rewritten if appropriate to optimize execution
* @throws net.sf.saxon.trans.XPathException if an error is discovered during this phase
* (typically a type error)
*/
@Override
public Pattern optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
return this;
}
}