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//------------------------------------------------------------------------------
// <copyright file="DescendantOverDescendantQuery.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
// <owner current="true" primary="true">Microsoft</owner>
//------------------------------------------------------------------------------
namespace MS.Internal.Xml.XPath {
using System;
using System.Xml;
using System.Xml.XPath;
using System.Diagnostics;
// DescendantOverDescendantQuery: for each input it looks for the topmost descendents that matches to ns:name
// This is posible when query which has this query as its input (child query) is descendent as well.
// Work of this query doesn't depend on DOD of its input.
// It doesn't garate DOD of the output even when input is DOD.
internal sealed class DescendantOverDescendantQuery : DescendantBaseQuery {
private int level = 0;
public DescendantOverDescendantQuery(Query qyParent, bool matchSelf, string name, string prefix, XPathNodeType typeTest, bool abbrAxis) :
base(qyParent, name, prefix, typeTest, matchSelf, abbrAxis) {}
private DescendantOverDescendantQuery(DescendantOverDescendantQuery other) : base(other) {
this.level = other.level;
}
public override void Reset() {
level = 0;
base.Reset();
}
public override XPathNavigator Advance() {
while (true) {
if (level == 0) {
currentNode = qyInput.Advance();
position = 0;
if (currentNode == null) {
return null;
}
if (matchSelf && matches(currentNode)) {
position = 1;
return currentNode;
}
currentNode = currentNode.Clone();
if (! MoveToFirstChild()) {
continue;
}
} else {
if (!MoveUpUntillNext()) {
continue;
}
}
do {
if (matches(currentNode)) {
position++;
return currentNode;
}
} while (MoveToFirstChild());
}
}
private bool MoveToFirstChild() {
if (currentNode.MoveToFirstChild()) {
level++;
return true;
}
return false;
}
private bool MoveUpUntillNext() { // move up untill we can move next
while (! currentNode.MoveToNext()) {
-- level;
if (level == 0) {
return false;
}
bool result = currentNode.MoveToParent();
Debug.Assert(result, "Algorithm error, We always should be able to move up if level > 0");
}
return true;
}
public override XPathNodeIterator Clone() { return new DescendantOverDescendantQuery(this); }
}
}
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