96 lines
4.1 KiB
C#
96 lines
4.1 KiB
C#
//------------------------------------------------------------------------------
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// <copyright file="precedingquery.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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namespace MS.Internal.Xml.XPath {
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using System;
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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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using System.Collections.Generic;
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using StackNav = ClonableStack<System.Xml.XPath.XPathNavigator>;
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// Algorithm:
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// Input assumption: qyInput is in DocOrder.
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// Preceding of a sequence of nodes will be preceding of last node in DocOrder in that sequence.
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// Because qyInput is in DO last input is last node in DO. -- "last"
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// If last node is attribute or namespace move last to it element.
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// Push this last node and all its ancestors into the ancestorStk. The root node will be the top-most element on the stack.
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// Create descendent iterator from the root. -- "workIterator"
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// Advancing workIterator we meet all nodes from the ancestorStk in stack order. Nodes in ancestorStk do no belong to the
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// the 'preceding' axis and must be ignored.
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// Last node in ancestorStk is a centinel node; when we pop it from ancestorStk, we should stop iterations.
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internal sealed class PrecedingQuery : BaseAxisQuery {
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private XPathNodeIterator workIterator;
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private StackNav ancestorStk;
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public PrecedingQuery(Query qyInput, string name, string prefix, XPathNodeType typeTest) : base(qyInput, name, prefix, typeTest) {
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ancestorStk = new StackNav();
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}
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private PrecedingQuery(PrecedingQuery other) : base(other) {
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this.workIterator = Clone(other.workIterator);
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this.ancestorStk = other.ancestorStk.Clone();
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}
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public override void Reset() {
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workIterator = null;
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ancestorStk.Clear();
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base.Reset();
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}
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public override XPathNavigator Advance() {
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if (workIterator == null) {
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XPathNavigator last; {
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XPathNavigator input = qyInput.Advance();
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if (input == null) {
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return null;
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}
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last = input.Clone();
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do {
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last.MoveTo(input);
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} while ((input = qyInput.Advance()) != null);
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if (last.NodeType == XPathNodeType.Attribute || last.NodeType == XPathNodeType.Namespace) {
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last.MoveToParent();
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}
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}
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// Fill ancestorStk :
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do {
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ancestorStk.Push(last.Clone());
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} while (last.MoveToParent());
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// Create workIterator :
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// last.MoveToRoot(); We are on root already
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workIterator = last.SelectDescendants(XPathNodeType.All, true);
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}
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while (workIterator.MoveNext()) {
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currentNode = workIterator.Current;
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if (currentNode.IsSamePosition(ancestorStk.Peek())) {
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ancestorStk.Pop();
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if (ancestorStk.Count == 0) {
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currentNode = null;
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workIterator = null;
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Debug.Assert(qyInput.Advance() == null, "we read all qyInput.Advance() already");
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return null;
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}
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continue;
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}
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if (matches(currentNode)) {
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position++;
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return currentNode;
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}
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}
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Debug.Fail("Algorithm error: we missed the centinel node");
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return null;
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}
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public override XPathNodeIterator Clone() { return new PrecedingQuery(this); }
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public override QueryProps Properties { get { return base.Properties | QueryProps.Reverse; } }
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}
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}
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