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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 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.ExpressionVisitor;
import net.sf.saxon.expr.parser.PromotionOffer;
import net.sf.saxon.functions.StringFn;
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;
import java.util.Iterator;
/**
* 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 {
// The select expression is adjusted to return xs:string?
// If the select expresion returns empty, then the node constructor returns empty.
/*@NotNull*/ protected Expression select;
/**
* Default constructor used by subclasses
*/
public SimpleNodeConstructor() {
select = Literal.makeEmptySequence(); // because a non-null value is needed
}
/**
* 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
* @param config the Saxon configuration (used for example to do early validation of the content
* of an attribute against the schema-defined type)
*/
public void setSelect(Expression select, Configuration config) {
this.select = select;
adoptChildExpression(select);
}
/**
* Get the expression that determines the string value of the constructed node
* @return the select expression
*/
public Expression getContentExpression() {
return select;
}
/**
* 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 select.getCardinality(); // may allow empty sequence
}
/*@NotNull*/
public Expression simplify(ExpressionVisitor visitor) throws XPathException {
select = visitor.simplify(select);
return this;
}
/**
* 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, ExpressionVisitor.ContextItemType 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
* @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, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
localTypeCheck(visitor, contextItemType);
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
select = visitor.typeCheck(select, contextItemType);
if (select instanceof ValueOf) {
Expression valSelect = ((ValueOf)select).getContentExpression();
if (th.isSubType(valSelect.getItemType(th), BuiltInAtomicType.STRING) &&
!Cardinality.allowsMany(valSelect.getCardinality())) {
select = valSelect;
}
}
// Don't bother converting untypedAtomic to string
if (select instanceof StringFn) {
StringFn fn = (StringFn)select;
Expression arg = fn.getArguments()[0];
if (arg.getItemType(th) == BuiltInAtomicType.UNTYPED_ATOMIC && !Cardinality.allowsMany(arg.getCardinality())) {
select = arg;
}
} else if (select instanceof CastExpression && ((CastExpression)select).getTargetType() == BuiltInAtomicType.STRING) {
Expression arg = ((CastExpression)select).getBaseExpression();
if (arg.getItemType(th) == BuiltInAtomicType.UNTYPED_ATOMIC && !Cardinality.allowsMany(arg.getCardinality())) {
select = arg;
}
}
adoptChildExpression(select);
return this;
}
/*@NotNull*/
public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
select = visitor.optimize(select, contextItemType);
if (select instanceof StringFn) {
StringFn sf = (StringFn)select;
TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
if (th.isSubType(sf.getArguments()[0].getItemType(th), BuiltInAtomicType.STRING) &&
!Cardinality.allowsMany(sf.getArguments()[0].getCardinality())) {
select = sf.getArguments()[0];
}
}
adoptChildExpression(select);
return this;
}
/*@NotNull*/
public Iterator iterateSubExpressions() {
return new MonoIterator(select);
}
/**
* Get the immediate sub-expressions of this expression, with information about the relationship
* of each expression to its parent expression. Default implementation
* returns a zero-length array, appropriate for an expression that has no
* sub-expressions.
*
* @return an iterator containing the sub-expressions of this expression
*/
@Override
public Iterator iterateSubExpressionInfo() {
return new MonoIterator(
new SubExpressionInfo(select, true, false, NODE_VALUE_CONTEXT));
}
/**
* 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;
}
return found;
}
/**
* 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 {
try {
CharSequence value = select.evaluateAsString(context);
processValue(value, context);
} catch (XPathException e) {
e.maybeSetLocation(this);
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 = select.evaluateItem(context);
String content;
if (contentItem == null) {
content = "";
} else {
content = contentItem.getStringValue();
content = checkContent(content, context);
}
final TypeHierarchy th = context.getConfiguration().getTypeHierarchy();
Orphan o = new Orphan(context.getConfiguration());
o.setNodeKind((short)getItemType(th).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
* @exception XPathException if any error is detected
*/
protected void promoteInst(PromotionOffer offer) throws XPathException {
select = doPromotion(select, offer);
super.promoteInst(offer);
}
}