/*
* @(#)$Id: ExceptOp.java 3619 2008-03-26 07:23:03Z yui $
*
* Copyright 2006-2008 Makoto YUI
*
* Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Contributors:
* Makoto YUI - initial implementation
*/
package xbird.xquery.expr.seq;
import xbird.xquery.TypeError;
import xbird.xquery.XQueryException;
import xbird.xquery.dm.value.*;
import xbird.xquery.dm.value.sequence.*;
import xbird.xquery.expr.XQExpression;
import xbird.xquery.meta.*;
import xbird.xquery.misc.TypeUtil;
import xbird.xquery.parser.XQueryParserVisitor;
import xbird.xquery.type.Type;
import xbird.xquery.type.TypeRegistry;
/**
* Constructs a sequence containing every node that occurs in the value of $parameter1,
* but not in the value of $parameter2, eliminating duplicate nodes.
* Nodes are returned in document order.
* <DIV lang="en"></DIV>
* <DIV lang="ja"></DIV>
*
* @author Makoto YUI (yuin405+xbird@gmail.com)
* @link http://www.w3.org/TR/xquery-operators/#func-except
*/
public final class ExceptOp extends SequenceOp {
private static final long serialVersionUID = -4777998184903330991L;
public ExceptOp(XQExpression leftOperand, XQExpression rightOperand) {
super(leftOperand, rightOperand, TypeRegistry.safeGet("node()*"));
}
public String getOperator() {
return "except";
}
@Override
public XQExpression visit(XQueryParserVisitor visitor, XQueryContext ctxt)
throws XQueryException {
return visitor.visit(this, ctxt);
}
@Override
public XQExpression staticAnalysis(StaticContext statEnv) throws XQueryException {
if(!_analyzed) {
this._analyzed = true;
this._leftOperand = _leftOperand.staticAnalysis(statEnv);
this._rightOperand = _rightOperand.staticAnalysis(statEnv);
final Type ltype = _leftOperand.getType();
if(!TypeUtil.subtypeOf(ltype, _type)) {
throw new TypeError("Inferred type of left operand is invalid: "
+ _leftOperand.getType());
}
if(!TypeUtil.subtypeOf(_rightOperand.getType(), _type)) {
throw new TypeError("Inferred type of left operand is invalid: "
+ _rightOperand.getType());
}
this._type = ltype;
}
return this;
}
public Sequence<? extends Item> eval(Sequence<? extends Item> contextSeq, DynamicContext dynEnv)
throws XQueryException {
// assume returned sequences are distinct ordered node sequence.
final Sequence<? extends Item> rawLeft = _leftOperand.eval(contextSeq, dynEnv);
final Sequence<XQNode> left = ProxyNodeSequence.wrap(rawLeft, dynEnv, true);
final Sequence<? extends Item> rawRight = _rightOperand.eval(contextSeq, dynEnv);
final Sequence<XQNode> right = ProxyNodeSequence.wrap(rawRight, dynEnv, true);
// If $parameter1 is the empty sequence, the empty sequence is returned.
if(left.isEmpty()) {
return ValueSequence.EMPTY_SEQUENCE;
}
// If $parameter2 is the empty sequence, a sequence is returned
// containing the nodes in $parameter1 in document order after eliminating duplicates.
if(right.isEmpty()) {
return DistinctSequence.wrap(left, dynEnv);
}
final ExceptEmuration res = new ExceptEmuration(left, right, dynEnv, _type);
return res;
}
private static final class ExceptEmuration extends AbstractSequence<XQNode> {
private static final long serialVersionUID = 1885734381391523775L;
private final Type type;
private final Sequence<XQNode> left, right;
private IFocus<XQNode> itor1, itor2;
private XQNode nextNode1, nextNode2;
public ExceptEmuration(Sequence<XQNode> left, Sequence<XQNode> right, DynamicContext dynEnv, Type type) {
super(dynEnv);
this.left = left;
this.right = right;
this.type = type;
}
@Override
public IFocus<XQNode> iterator() {
this.itor1 = left.iterator();
this.itor2 = right.iterator();
this.nextNode1 = itor1.hasNext() ? itor1.next() : null;
this.nextNode2 = itor2.hasNext() ? itor2.next() : null;
return new Focus<XQNode>(this, _dynEnv);
}
public boolean next(IFocus<XQNode> focus) throws XQueryException {
while(true) {
if(nextNode1 == null) {
itor1.closeQuietly();
itor2.closeQuietly();
return false;
} else {
if(nextNode2 == null) {
focus.setContextItem(nextNode1);
this.nextNode1 = itor1.hasNext() ? itor1.next() : null;
return true;
} else {// both items exists
int cmp = nextNode1.compareTo(nextNode2);
if(cmp == 0) {// skip both item
this.nextNode1 = itor1.hasNext() ? itor1.next() : null;
if(itor2.hasNext()) {
this.nextNode2 = itor2.next();
}
} else if(cmp < 0) {
focus.setContextItem(nextNode1);
this.nextNode1 = itor1.hasNext() ? itor1.next() : null;
return true;
} else {// skip right item
this.nextNode2 = itor2.hasNext() ? itor2.next() : null;
}
}
}
}
}
public Type getType() {
return type;
}
}
}