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The XSLT and XQuery Processor
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 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.expr.instruct;
import net.sf.saxon.Configuration;
import net.sf.saxon.expr.*;
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.functions.String_1;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.NodeName;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.iter.SingletonIterator;
import net.sf.saxon.tree.util.Orphan;
import net.sf.saxon.type.BuiltInAtomicType;
import net.sf.saxon.type.TypeHierarchy;
import net.sf.saxon.value.Cardinality;
/**
* Common superclass for XSLT instructions whose content template produces a text
* value: xsl:attribute, xsl:comment, xsl:processing-instruction, xsl:namespace,
* and xsl:text, and their XQuery equivalents
*/
public abstract class SimpleNodeConstructor extends Instruction {
protected Operand selectOp;
/**
* Default constructor used by subclasses
*/
public SimpleNodeConstructor() {
Expression select = Literal.makeEmptySequence();
selectOp = new Operand(this, select, OperandRole.SINGLE_ATOMIC);
}
/**
* Set the select expression: the value of this expression determines the string-value of the node
*
* @param select the expression that computes the string value of the node
*
*/
public void setSelect(Expression select) {
selectOp.setChildExpression(select);
}
/**
* Get the select expression, that is the expression that computes the content of the constructed node.
* Note that this may correspond either to a select attribute or a contained sequence constructor
* in the case of XSLT; and in XQuery it corresponds to whatever expression is contained in the node
* constructpr.
* @return the expression used to compute the content of the node.
*/
public Expression getSelect() {
return selectOp.getChildExpression();
}
@Override
public Iterable operands() {
return selectOp;
}
/**
* Determine whether this instruction creates new nodes.
* This implementation returns true.
*/
public final boolean createsNewNodes() {
return true;
}
/**
* Get the cardinality of the sequence returned by evaluating this instruction
*
* @return the static cardinality
*/
public int computeCardinality() {
return getSelect().getCardinality(); // may allow empty sequence
}
/**
* Get the static properties of this expression (other than its type). The result is
* bit-signficant. These properties are used for optimizations. In general, if
* property bit is set, it is true, but if it is unset, the value is unknown.
*
* @return a set of flags indicating static properties of this expression
*/
public int computeSpecialProperties() {
return super.computeSpecialProperties() |
StaticProperty.SINGLE_DOCUMENT_NODESET;
}
/**
* Method to perform type-checking specific to the kind of instruction
*
* @param visitor an expression visitor
* @param contextItemType the static type of the context item
* @throws XPathException if a type error is detected
*/
public abstract void localTypeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) throws XPathException;
/**
* The typeCheck() method is called in XQuery, where node constructors
* are implemented as Expressions. In this case the required type for the
* select expression is a single string.
*
*
param visitor an expression visitor
* @param contextInfo information about the dynamic context
* @return the rewritten expression
* @throws XPathException if any static errors are found in this expression
* or any of its children
*/
/*@NotNull*/
public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException {
typeCheckChildren(visitor, contextInfo);
localTypeCheck(visitor, contextInfo);
final TypeHierarchy th = getConfiguration().getTypeHierarchy();
if (getSelect() instanceof ValueOf) {
Expression valSelect = ((ValueOf) getSelect()).getSelect();
if (th.isSubType(valSelect.getItemType(), BuiltInAtomicType.STRING) &&
!Cardinality.allowsMany(valSelect.getCardinality())) {
setSelect(valSelect);
}
}
// Don't bother converting untypedAtomic to string
if (getSelect().isCallOn(String_1.class)) {
SystemFunctionCall fn = (SystemFunctionCall) getSelect();
Expression arg = fn.getArg(0);
if (arg.getItemType() == BuiltInAtomicType.UNTYPED_ATOMIC && !Cardinality.allowsMany(arg.getCardinality())) {
setSelect(arg);
}
} else if (getSelect() instanceof CastExpression && ((CastExpression) getSelect()).getTargetType() == BuiltInAtomicType.STRING) {
Expression arg = ((CastExpression) getSelect()).getBaseExpression();
if (arg.getItemType() == BuiltInAtomicType.UNTYPED_ATOMIC && !Cardinality.allowsMany(arg.getCardinality())) {
setSelect(arg);
}
}
adoptChildExpression(getSelect());
return this;
}
/*@NotNull*/
public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) throws XPathException {
optimizeChildren(visitor, contextItemType);
if (getSelect().isCallOn(String_1.class)) {
SystemFunctionCall sf = (SystemFunctionCall) getSelect();
TypeHierarchy th = getConfiguration().getTypeHierarchy();
if (th.isSubType(sf.getArg(0).getItemType(), BuiltInAtomicType.STRING) &&
!Cardinality.allowsMany(sf.getArg(0).getCardinality())) {
setSelect(sf.getArg(0));
}
}
return this;
}
/**
* Process this instruction
*
* @param context the dynamic context of the transformation
* @return a TailCall to be executed by the caller, always null for this instruction
*/
public TailCall processLeavingTail(XPathContext context) throws XPathException {
CharSequence value;
if (getHostLanguage() == Configuration.XSLT && getPackageData().getXPathVersion() < 30) {
int savedOutputState = context.getTemporaryOutputState();
context.setTemporaryOutputState(getInstructionNameCode());
value = getSelect().evaluateAsString(context);
context.setTemporaryOutputState(savedOutputState);
} else {
value = getSelect().evaluateAsString(context);
}
try {
processValue(value, context);
} catch (XPathException e) {
e.maybeSetLocation(getLocation());
throw e;
}
return null;
}
/**
* Process the value of the node, to create the new node.
*
* @param value the string value of the new node
* @param context the dynamic evaluation context
* @throws XPathException if a dynamic error occurs
*/
public abstract void processValue(CharSequence value, XPathContext context) throws XPathException;
/**
* Evaluate as an expression.
*/
public Item evaluateItem(XPathContext context) throws XPathException {
Item contentItem;
if (getHostLanguage() == Configuration.XSLT && getRetainedStaticContext().getXPathVersion() < 30) {
int savedOutputState = context.getTemporaryOutputState();
context.setTemporaryOutputState(getInstructionNameCode());
contentItem = getSelect().evaluateItem(context);
context.setTemporaryOutputState(savedOutputState);
} else {
contentItem = getSelect().evaluateItem(context);
}
String content;
if (contentItem == null) {
content = "";
} else {
content = contentItem.getStringValue();
content = checkContent(content, context);
}
Orphan o = new Orphan(context.getConfiguration());
o.setNodeKind((short) getItemType().getPrimitiveType());
o.setStringValue(content);
o.setNodeName(evaluateNodeName(context));
return o;
}
/**
* Check the content of the node, and adjust it if necessary. The checks depend on the node kind.
*
* @param data the supplied content
* @param context the dynamic context
* @return the original content, unless adjustments are needed
* @throws XPathException if the content is invalid
*/
protected String checkContent(String data, XPathContext context) throws XPathException {
return data;
}
/**
* Run-time method to compute the name of the node being constructed. This is overridden
* for nodes that have a name. The default implementation returns -1, which is suitable for
* unnamed nodes such as comments
*
* @param context the XPath dynamic evaluation context
* @return the name pool nameCode identifying the name of the constructed node
* @throws XPathException if any failure occurs
*/
public NodeName evaluateNodeName(XPathContext context) throws XPathException {
return null;
}
/*@NotNull*/
public SequenceIterator iterate(XPathContext context) throws XPathException {
return SingletonIterator.makeIterator(evaluateItem(context));
}
/**
* Offer promotion for subexpressions. 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.
*
* @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
* @throws XPathException if any error is detected
*/
protected void promoteChildren(PromotionOffer offer) throws XPathException {
setSelect(doPromotion(getSelect(), offer));
super.promoteChildren(offer);
}
}
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