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//------------------------------------------------------------------------------
// <copyright file="precedingsibling.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;
using System.Collections.Generic;
// This class can be rewritten much more efficient.
// Algorithm could be like one for FollowingSibling:
// - Build InputArrays: pares (first, sentinel)
// -- Cash all input nodes as sentinel
// -- Add firts node of its parent for each input node.
// -- Sort these pares by first nodes.
// - Advance algorithm will look like:
// -- For each row in InputArays we will output first node + all its following nodes which are < sentinel
// -- Before outputing each node in row #I we will check that it is < first node in row #I+1
// --- if true we actualy output it
// --- if false, we hold with row #I and apply this algorith starting for row #I+1
// --- when we done with #I+1 we continue with row #I
internal class PreSiblingQuery : CacheAxisQuery {
public PreSiblingQuery(Query qyInput, string name, string prefix, XPathNodeType typeTest) : base (qyInput, name, prefix, typeTest) {}
protected PreSiblingQuery(PreSiblingQuery other) : base(other) {}
private bool NotVisited(XPathNavigator nav, List<XPathNavigator> parentStk){
XPathNavigator nav1 = nav.Clone();
nav1.MoveToParent();
for (int i = 0; i < parentStk.Count; i++) {
if (nav1.IsSamePosition(parentStk[i])) {
return false;
}
}
parentStk.Add(nav1);
return true;
}
public override object Evaluate(XPathNodeIterator context) {
base.Evaluate(context);
// Fill up base.outputBuffer
List<XPathNavigator> parentStk = new List<XPathNavigator>();
Stack<XPathNavigator> inputStk = new Stack<XPathNavigator>();
while ((currentNode = qyInput.Advance()) != null) {
inputStk.Push(currentNode.Clone());
}
while (inputStk.Count != 0) {
XPathNavigator input = inputStk.Pop();
if (input.NodeType == XPathNodeType.Attribute || input.NodeType == XPathNodeType.Namespace) {
continue;
}
if (NotVisited(input, parentStk)) {
XPathNavigator prev = input.Clone();
if (prev.MoveToParent()) {
bool test = prev.MoveToFirstChild();
Debug.Assert(test, "We just moved to parent, how we can not have first child?");
while (!prev.IsSamePosition(input)) {
if (matches(prev)) {
Insert(outputBuffer, prev);
}
if (!prev.MoveToNext()) {
Debug.Fail("We managed to miss sentinel node (input)");
break;
}
}
}
}
}
return this;
}
public override XPathNodeIterator Clone() { return new PreSiblingQuery(this); }
public override QueryProps Properties { get { return base.Properties | QueryProps.Reverse; } }
}
}
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