77 lines
3.1 KiB
C#
77 lines
3.1 KiB
C#
//------------------------------------------------------------------------------
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// <copyright file="DocumentOrderComparer.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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// <owner current="true" primary="true">[....]</owner>
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//------------------------------------------------------------------------------
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using System;
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using System.Collections;
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using System.Collections.Generic;
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using System.Xml;
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using System.Xml.XPath;
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using System.Diagnostics;
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namespace System.Xml.Xsl.Runtime {
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/// <summary>
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/// IComparer implementation that orders navigators based on ComparePosition. When ComparePosition returns
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/// XmlNodeOrder.Unknown, a stable order between documents is maintained by an ordered list mapping each root node
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/// to an ordering index.
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/// </summary>
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internal class DocumentOrderComparer : IComparer<XPathNavigator> {
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private List<XPathNavigator> roots;
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/// <summary>
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/// Return:
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/// -1 if navThis is positioned before navThat
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/// 0 if navThis has the same position as navThat
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/// 1 if navThis is positioned after navThat
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/// </summary>
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public int Compare(XPathNavigator navThis, XPathNavigator navThat) {
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switch (navThis.ComparePosition(navThat)) {
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case XmlNodeOrder.Before: return -1;
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case XmlNodeOrder.Same: return 0;
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case XmlNodeOrder.After: return 1;
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}
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// Use this.roots to impose stable ordering
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if (this.roots == null)
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this.roots = new List<XPathNavigator>();
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Debug.Assert(GetDocumentIndex(navThis) != GetDocumentIndex(navThat));
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return GetDocumentIndex(navThis) < GetDocumentIndex(navThat) ? -1 : 1;
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}
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/// <summary>
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/// Map navigator's document to a unique index.
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/// When consecutive calls are made to GetIndexOfNavigator for navThis and navThat, it is not possible
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/// for them to return the same index. navThis compared to navThat is always XmlNodeOrder.Unknown.
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/// Therefore, no matter where navThis is inserted in the list, navThat will never be inserted just
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/// before navThis, and therefore will never have the same index.
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/// </summary>
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public int GetDocumentIndex(XPathNavigator nav) {
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XPathNavigator navRoot;
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// Use this.roots to impose stable ordering
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if (this.roots == null)
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this.roots = new List<XPathNavigator>();
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// Position navigator to root
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navRoot = nav.Clone();
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navRoot.MoveToRoot();
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for (int idx = 0; idx < this.roots.Count; idx++) {
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if (navRoot.IsSamePosition(this.roots[idx])) {
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// navigator's document was previously mapped to a unique index
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return idx;
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}
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}
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// Add navigator to this.roots mapping
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this.roots.Add(navRoot);
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return this.roots.Count - 1;
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}
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}
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}
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