net.sf.saxon.instruct.ForEach Maven / Gradle / Ivy
package net.sf.saxon.instruct;
import net.sf.saxon.Controller;
import net.sf.saxon.expr.*;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.om.StandardNames;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trace.TraceListener;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.SchemaType;
import net.sf.saxon.type.TypeHierarchy;
import java.util.Iterator;
/**
* Handler for xsl:for-each elements in a stylesheet.
*/
public class ForEach extends Instruction implements ContextMappingFunction {
private Expression select;
private Expression action;
/**
* Create an xsl:for-each instruction
* @param select the select expression
* @param action the body of the xsl:for-each loop
*/
public ForEach(Expression select, Expression action) {
this.select = select;
this.action = action;
adoptChildExpression(select);
adoptChildExpression(action);
}
/**
* Get the name of this instruction for diagnostic and tracing purposes
* @return the code for name xsl:for-each
*/
public int getInstructionNameCode() {
return StandardNames.XSL_FOR_EACH;
}
/**
* Get the action expression (the content of the for-each)
* @return the body of the for-each loop
*/
public Expression getActionExpression() {
return action;
}
/**
* Determine the data type of the items returned by this expression
* @return the data type
* @param th the type hierarchy cache
*/
public final ItemType getItemType(TypeHierarchy th) {
return action.getItemType(th);
}
/**
* Determine whether this instruction creates new nodes.
* This implementation returns true if the "action" creates new nodes.
* (Nodes created by the condition can't contribute to the result).
*/
public final boolean createsNewNodes() {
int props = action.getSpecialProperties();
return ((props & StaticProperty.NON_CREATIVE) == 0);
}
/**
* Simplify an expression. This performs any static optimization (by rewriting the expression
* as a different expression).
*
* @exception XPathException if an error is discovered during expression
* rewriting
* @return the simplified expression
* @param visitor the expression visitor
*/
public Expression simplify(ExpressionVisitor visitor) throws XPathException {
select = visitor.simplify(select);
action = visitor.simplify(action);
return this;
}
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
select = visitor.typeCheck(select, contextItemType);
adoptChildExpression(select);
action = visitor.typeCheck(action, select.getItemType(th));
adoptChildExpression(action);
if (Literal.isEmptySequence(select)) {
return select;
}
if (Literal.isEmptySequence(action)) {
return action;
}
return this;
}
public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException {
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
select = visitor.optimize(select, contextItemType);
adoptChildExpression(select);
action = action.optimize(visitor, select.getItemType(th));
adoptChildExpression(action);
if (Literal.isEmptySequence(select)) {
return select;
}
if (Literal.isEmptySequence(action)) {
return action;
}
// If any subexpressions within the body of the for-each are not dependent on the focus,
// promote them: this causes them to be evaluated once, outside the for-each loop
PromotionOffer offer = new PromotionOffer(visitor.getConfiguration().getOptimizer());
offer.action = PromotionOffer.FOCUS_INDEPENDENT;
offer.promoteDocumentDependent = (select.getSpecialProperties() & StaticProperty.CONTEXT_DOCUMENT_NODESET) != 0;
offer.promoteXSLTFunctions = false;
offer.containingExpression = this;
action = doPromotion(action, offer);
if (offer.containingExpression instanceof LetExpression) {
offer.containingExpression =
visitor.optimize(offer.containingExpression, contextItemType);
}
return offer.containingExpression;
}
/**
* Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited
* by an expression in a source tree.
*
* The default implementation of this method assumes that an expression does no navigation other than
* the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the
* same context as the containing expression. The method must be overridden for any expression
* where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression,
* and RootExpression (because they perform navigation), and for the doc(), document(), and collection()
* functions because they create a new navigation root. Implementations also exist for PathExpression and
* FilterExpression because they have subexpressions that are evaluated in a different context from the
* calling expression.
*
* @param pathMap the PathMap to which the expression should be added
* @param pathMapNodeSet
* @return the pathMapNode representing the focus established by this expression, in the case where this
* expression is the first operand of a path expression or filter expression. For an expression that does
* navigation, it represents the end of the arc in the path map that describes the navigation route. For other
* expressions, it is the same as the input pathMapNode.
*/
public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) {
PathMap.PathMapNodeSet target = select.addToPathMap(pathMap, pathMapNodeSet);
return action.addToPathMap(pathMap, target);
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
public Expression copy() {
return new ForEach(select.copy(), action.copy());
}
/**
* Compute the dependencies of an expression, as the union of the
* dependencies of its subexpressions. (This is overridden for path expressions
* and filter expressions, where the dependencies of a subexpression are not all
* propogated). This method should be called only once, to compute the dependencies;
* after that, getDependencies should be used.
*
* @return the depencies, as a bit-mask
*/
public int computeDependencies() {
// Some of the dependencies aren't relevant. Note that the sort keys are absorbed into the select
// expression.
int dependencies = 0;
dependencies |= select.getDependencies();
dependencies |= (action.getDependencies() & ~StaticProperty.DEPENDS_ON_FOCUS);
return dependencies;
}
/**
* Handle promotion offers, that is, non-local tree rewrites.
* @param offer The type of rewrite being offered
* @throws XPathException
*/
protected void promoteInst(PromotionOffer offer) throws XPathException {
select = doPromotion(select, offer);
action = doPromotion(action, offer);
}
/**
* Get all the XPath expressions associated with this instruction
* (in XSLT terms, the expression present on attributes of the instruction,
* as distinct from the child instructions in a sequence construction)
*/
public Iterator iterateSubExpressions() {
return new PairIterator(select, action);
}
/**
* Given an expression that is an immediate child of this expression, test whether
* the evaluation of the parent expression causes the child expression to be
* evaluated repeatedly
* @param child the immediate subexpression
* @return true if the child expression is evaluated repeatedly
*/
public boolean hasLoopingSubexpression(Expression child) {
return child == action;
}
/**
* 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 (select == original) {
select = replacement;
found = true;
}
if (action == original) {
action = replacement;
found = true;
}
return found;
}
/**
* An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
* This method indicates which of these methods is provided. This implementation provides both iterate() and
* process() methods natively.
*/
public int getImplementationMethod() {
return ITERATE_METHOD | PROCESS_METHOD;
}
/**
* Check that any elements and attributes constructed or returned by this expression are acceptable
* in the content model of a given complex type. It's always OK to say yes, since the check will be
* repeated at run-time. The process of checking element and attribute constructors against the content
* model of a complex type also registers the type of content expected of those constructors, so the
* static validation can continue recursively.
*/
public void checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole) throws XPathException {
action.checkPermittedContents(parentType, env, false);
}
public TailCall processLeavingTail(XPathContext context) throws XPathException {
Controller controller = context.getController();
SequenceIterator iter = select.iterate(context);
XPathContextMajor c2 = context.newContext();
c2.setOrigin(this);
c2.setCurrentIterator(iter);
c2.setCurrentTemplateRule(null);
if (controller.isTracing()) {
TraceListener listener = controller.getTraceListener();
while(true) {
Item item = iter.next();
if (item == null) {
break;
}
listener.startCurrentItem(item);
action.process(c2);
listener.endCurrentItem(item);
}
} else {
while(true) {
Item item = iter.next();
if (item == null) {
break;
}
action.process(c2);
}
}
return null;
}
/**
* Return an Iterator to iterate over the values of the sequence.
*
* @exception XPathException if any dynamic error occurs evaluating the
* expression
* @param context supplies the context for evaluation
* @return a SequenceIterator that can be used to iterate over the result
* of the expression
*/
public SequenceIterator iterate(XPathContext context) throws XPathException {
SequenceIterator master = select.iterate(context);
XPathContextMajor c2 = context.newContext();
c2.setOrigin(this);
c2.setCurrentTemplateRule(null);
c2.setCurrentIterator(master);
master = new ContextMappingIterator(this, c2);
return master;
}
/**
* Map one item to a sequence.
* @param context The processing context. This is supplied only for mapping constructs that
* set the context node, position, and size. Otherwise it is null.
* @return either (a) a SequenceIterator over the sequence of items that the supplied input
* item maps to, or (b) an Item if it maps to a single item, or (c) null if it maps to an empty
* sequence.
*/
public SequenceIterator map(XPathContext context) throws XPathException {
return action.iterate(context);
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public void explain(ExpressionPresenter out) {
out.startElement("forEach");
select.explain(out);
out.startSubsidiaryElement("return");
action.explain(out);
out.endSubsidiaryElement();
out.endElement();
}
}
//
// The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
// you may not use this file except in compliance with the License. You may obtain a copy of the
// License at http://www.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied.
// See the License for the specific language governing rights and limitations under the License.
//
// The Original Code is: all this file.
//
// The Initial Developer of the Original Code is Michael H. Kay.
//
// Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
//
// Contributor(s): none.
//
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