CacheChildrenQuery.cs source code in C# .NET

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                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / Xml / System / Xml / XPath / Internal / CacheChildrenQuery.cs / 1 / CacheChildrenQuery.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// [....] 
//-----------------------------------------------------------------------------
 
namespace MS.Internal.Xml.XPath { 
    using System;
    using System.Xml; 
    using System.Xml.XPath;
    using System.Diagnostics;
    using System.Globalization;
    using System.Collections.Generic; 
    using StackInt = ClonableStack;
    using StackNav = ClonableStack; 
 
    // This class implements Children axis on Ancestor & Descendant imputs. (as well as id(), preciding, following)
    // The problem here is that is descenant::*/child::* and ancestor::*/child::* can produce duplicates nodes 
    // The algorithm havily uses the fact that in our implementation of both AncestorQuery and DecsndantQuery return nodes in document order.
    // As result first child is always before or equal of next input.
    // So we don't need to call DecideNextNode() when needInput == true && stack is empty.
    internal sealed class CacheChildrenQuery : ChildrenQuery { 
        XPathNavigator nextInput = null;
        StackNav elementStk; 
        StackInt positionStk; 
        bool needInput;
#if DEBUG 
        XPathNavigator lastNode = null;
#endif

        public CacheChildrenQuery(Query qyInput, string name, string prefix, XPathNodeType type) : base(qyInput, name, prefix, type) { 
            this.elementStk  = new StackNav();
            this.positionStk = new StackInt(); 
            this.needInput   = true; 
        }
        private CacheChildrenQuery(CacheChildrenQuery other) : base(other) { 
            this.nextInput   = Clone(other.nextInput);
            this.elementStk  = other.elementStk.Clone();
            this.positionStk = other.positionStk.Clone();
            this.needInput   = other.needInput; 
#if DEBUG
            this.lastNode    = Clone(other.lastNode); 
#endif 
        }
 
        public override void Reset() {
            nextInput = null;
            elementStk.Clear();
            positionStk.Clear(); 
            needInput = true;
            base.Reset(); 
#if DEBUG 
            lastNode = null;
#endif 
        }

        public override XPathNavigator Advance() {
            do { 
                if (needInput) {
                    if (elementStk.Count == 0) { 
                        currentNode = GetNextInput(); 
                        if (currentNode == null) {
                            return null; 
                        }
                        if (!currentNode.MoveToFirstChild()) {
                            continue;
                        } 
                        position = 0;
                    } else { 
                        currentNode = elementStk .Pop(); 
                        position    = positionStk.Pop();
                        if (!DecideNextNode()) { 
                            continue;
                        }
                    }
                    needInput = false; 
                } else {
                    if (!currentNode.MoveToNext() || !DecideNextNode()) { 
                        needInput = true; 
                        continue;
                    } 
                }
#if DEBUG
                if (lastNode != null) {
                    if (currentNode.GetType().ToString() == "Microsoft.VisualStudio.Modeling.StoreNavigator") { 
                        XmlNodeOrder order = CompareNodes(lastNode, currentNode);
                        Debug.Assert(order == XmlNodeOrder.Before, "Algorith error. Nodes expected to be DocOrderDistinct"); 
                    } 
                }
                lastNode = currentNode.Clone(); 
#endif
                if (matches(currentNode)) {
                    position++;
                    return currentNode; 
                }
            } while (true); 
        } // Advance 

        private bool DecideNextNode() { 
            nextInput = GetNextInput();
            if (nextInput != null) {
                if (CompareNodes(currentNode, nextInput) == XmlNodeOrder.After) {
                    elementStk .Push(currentNode); 
                    positionStk.Push(position);
                    currentNode = nextInput; 
                    nextInput = null; 
                    if (!currentNode.MoveToFirstChild()) {
                        return false; 
                    }
                    position = 0;
                }
            } 
            return true;
        } 
 
        private XPathNavigator GetNextInput() {
            XPathNavigator result; 
            if (nextInput != null) {
                result = nextInput;
                nextInput = null;
            } else { 
                result = qyInput.Advance();
                if (result != null) { 
                    result = result.Clone(); 
                }
            } 
            return result;
        }

        public override XPathNodeIterator Clone() { return new CacheChildrenQuery(this); } 
    } // Children Query}
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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CacheChildrenQuery.cs source code in C# .NET

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