package net.sf.saxon.expr;
import net.sf.saxon.om.Axis;
import net.sf.saxon.om.DocumentInfo;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.NodeInfo;
import net.sf.saxon.pattern.NodeKindTest;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.TypeHierarchy;
/**
* An expression whose value is always a set of nodes containing a single node,
* the document root. This corresponds to the XPath Expression "/", including the implicit
* "/" at the start of a path expression with a leading "/".
*/
public class RootExpression extends SingleNodeExpression {
/**
* Customize the error message on type checking
*/
protected String noContextMessage() {
return "Leading '/' cannot select the root node of the tree containing the context item";
}
/**
* Is this expression the same as another expression?
*/
public boolean equals(Object other) {
return (other instanceof RootExpression);
}
/**
* Specify that the expression returns a singleton
*/
public final int computeCardinality() {
return StaticProperty.EXACTLY_ONE;
}
/**
* Determine the data type of the items returned by this expression
*
* @return Type.NODE
* @param th the type hierarchy cache
*/
public ItemType getItemType(TypeHierarchy th) {
return NodeKindTest.DOCUMENT;
}
/**
* get HashCode for comparing two expressions
*/
public int hashCode() {
return "RootExpression".hashCode();
}
/**
* Return the first element selected by this Expression
* @param context The evaluation context
* @return the NodeInfo of the first selected element, or null if no element
* is selected
*/
public NodeInfo getNode(XPathContext context) throws XPathException {
Item current = context.getContextItem();
if (current==null) {
dynamicError("Finding root of tree: the context item is undefined", "XPDY0002", context);
}
if (current instanceof NodeInfo) {
DocumentInfo doc = ((NodeInfo)current).getDocumentRoot();
if (doc==null) {
dynamicError("The root of the tree containing the context item is not a document node", "XPDY0050", context);
}
return doc;
}
typeError("Finding root of tree: the context item is not a node", "XPTY0020", context);
// dummy return; we never get here
return null;
}
/**
* Determine which aspects of the context the expression depends on. The result is
* a bitwise-or'ed value composed from constants such as StaticProperty.VARIABLES and
* StaticProperty.CURRENT_NODE
*/
public int getIntrinsicDependencies() {
return StaticProperty.DEPENDS_ON_CONTEXT_DOCUMENT;
}
/**
* Copy an expression. This makes a deep copy.
* @return the copy of the original expression
*/
public Expression copy() {
return new RootExpression();
}
/**
* 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.
*
* @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
*/
public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) {
if (pathMapNodeSet == null) {
ContextItemExpression cie = new ContextItemExpression();
cie.setContainer(getContainer());
pathMapNodeSet = new PathMap.PathMapNodeSet(pathMap.makeNewRoot(cie));
}
AxisExpression root = new AxisExpression(Axis.ANCESTOR_OR_SELF, NodeKindTest.DOCUMENT);
root.setContainer(getContainer());
return root.addToPathMap(pathMap, pathMapNodeSet);
// if (pathMapNodeSet == null) {
// return new PathMap.PathMapNodeSet(pathMap.makeNewRoot(this));
// } else {
// AxisExpression root = new AxisExpression(Axis.ANCESTOR_OR_SELF, NodeKindTest.DOCUMENT);
// root.setContainer(getContainer());
// return root.addToPathMap(pathMap, pathMapNodeSet);
// }
}
/**
* The toString() method for an expression attempts to give a representation of the expression
* in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
* In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax
*/
public String toString() {
return "(/)";
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public void explain(ExpressionPresenter destination) {
destination.startElement("root");
destination.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.
//