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An OSGi bundle for Saxon-HE
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 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;
import net.sf.saxon.Configuration;
import net.sf.saxon.expr.parser.ExpressionTool;
import net.sf.saxon.expr.parser.ExpressionVisitor;
import net.sf.saxon.expr.parser.PromotionOffer;
import net.sf.saxon.expr.parser.Token;
import net.sf.saxon.om.AxisInfo;
import net.sf.saxon.om.GroundedValue;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.pattern.NodeTest;
import net.sf.saxon.pattern.Pattern;
import net.sf.saxon.pattern.SimplePositionalPattern;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.Type;
import net.sf.saxon.type.TypeHierarchy;
import net.sf.saxon.value.Int64Value;
import net.sf.saxon.value.SequenceExtent;
import java.util.Iterator;
import java.util.List;
/**
* A TailExpression represents a FilterExpression of the form EXPR[position() > n]
* Here n is usually 2, but we allow other values
*/
public class TailExpression extends Expression {
/*@Nullable*/ Expression base;
int start; // 1-based offset of first item from base expression
// to be included
/**
* Construct a TailExpression, representing a filter expression of the form
* $base[position() >= $start]
* @param base the expression to be filtered
* @param start the position (1-based) of the first item to be included
*/
public TailExpression(Expression base, int start) {
this.base = base;
this.start = start;
adoptChildExpression(base);
}
/*@NotNull*/
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
base = visitor.typeCheck(base, contextItemType);
return this;
}
/*@NotNull*/
public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
base = visitor.optimize(base, contextItemType);
if (base instanceof Literal) {
GroundedValue value =
SequenceExtent.makeSequenceExtent(iterate(visitor.getStaticContext().makeEarlyEvaluationContext()));
return Literal.makeLiteral(value);
}
return this;
}
public Expression promote(PromotionOffer offer, Expression parent) throws XPathException {
Expression exp = offer.accept(parent, this);
if (exp != null) {
return exp;
} else {
if (offer.action != PromotionOffer.UNORDERED) {
base = doPromotion(base, offer);
}
return this;
}
}
public int computeSpecialProperties() {
return base.getSpecialProperties();
}
/**
* Copy an expression. This makes a deep copy.
*
* @return the copy of the original expression
*/
/*@NotNull*/
public Expression copy() {
return new TailExpression(base.copy(), start);
}
/*@NotNull*/
public ItemType getItemType(TypeHierarchy th) {
return base.getItemType(th);
}
public int computeCardinality() {
return base.getCardinality() | StaticProperty.ALLOWS_ZERO;
}
/*@NotNull*/
public Iterator iterateSubExpressions() {
return new MonoIterator(base);
}
/**
* 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 (base == original) {
base = replacement;
found = true;
}
return found;
}
/**
* Get the base expression (of which this expression returns the tail part of the value)
* @return the base expression
*/
public Expression getBaseExpression() {
return base;
}
/**
* Get the start offset
* @return the one-based start offset (returns 2 if all but the first item is being selected)
*/
public int getStart() {
return start;
}
/**
* Compare two expressions to see if they are equal
* @param other the other expression
* @return true if the expressions are equivalent
*/
public boolean equals(Object other) {
return other instanceof TailExpression &&
base.equals(((TailExpression)other).base) &&
start == ((TailExpression)other).start;
}
public int hashCode() {
return base.hashCode();
}
/*@NotNull*/
public SequenceIterator iterate(XPathContext context) throws XPathException {
SequenceIterator baseIter = base.iterate(context);
return TailIterator.make(baseIter, start);
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public void explain(ExpressionPresenter destination) {
destination.startElement("tail");
destination.emitAttribute("start", start+"");
base.explain(destination);
destination.endElement();
}
/**
* The toString() method for an expression attempts to give a representation of the expression
* in an XPath-like form.
*
* For subclasses of Expression that represent XPath expressions, the result should always be a string that
* parses as an XPath 3.0 expression.
*
* @return a representation of the expression as a string
*/
@Override
public String toString() {
if (start == 2) {
return "tail(" + base.toString() + ")";
} else {
return ExpressionTool.parenthesize(base) + "[position() ge " + start + "]";
}
}
}