mcs/class/referencesource/System.Data.SqlXml/System/Xml/Xsl/QIL/QilCloneVisitor.cs

   1 //------------------------------------------------------------------------------
   2 // <copyright file="QilCloneVisitor.cs" company="Microsoft">
   3 //     Copyright (c) Microsoft Corporation.  All rights reserved.
   4 // </copyright>
   5 // <owner current="true" primary="true">Microsoft</owner>
   6 //------------------------------------------------------------------------------
   7
   8 using System;
   9 using System.Collections.Generic;
  10 using System.Diagnostics;
  11 using System.Xml;
  12 using System.Xml.Xsl;
  13
  14 namespace System.Xml.Xsl.Qil {
  15
  16     // Create an exact replica of a QIL graph
  17     internal class QilCloneVisitor : QilScopedVisitor {
  18         private QilFactory fac;
  19         private SubstitutionList subs;
  20
  21
  22         //-----------------------------------------------
  23         // Constructors
  24         //-----------------------------------------------
  25
  26         public QilCloneVisitor(QilFactory fac) : this(fac, new SubstitutionList()) {
  27         }
  28
  29         public QilCloneVisitor(QilFactory fac, SubstitutionList subs) {
  30             this.fac = fac;
  31             this.subs = subs;
  32         }
  33
  34
  35         //-----------------------------------------------
  36         // Entry
  37         //-----------------------------------------------
  38
  39         public QilNode Clone(QilNode node) {
  40             QilDepthChecker.Check(node);
  41             // Assume that iterator nodes at the top-level are references rather than definitions
  42             return VisitAssumeReference(node);
  43         }
  44
  45
  46         //-----------------------------------------------
  47         // QilVisitor overrides
  48         //-----------------------------------------------
  49
  50         /// <summary>
  51         /// Visit all children of "parent", replacing each child with a copy of each child.
  52         /// </summary>
  53         protected override QilNode Visit(QilNode oldNode) {
  54             QilNode newNode = null;
  55
  56             if (oldNode == null)
  57                 return null;
  58
  59             // ShallowClone any nodes which have not yet been cloned
  60             if (oldNode is QilReference) {
  61                 // Reference nodes may have been cloned previously and put into scope
  62                 newNode = FindClonedReference(oldNode);
  63             }
  64
  65             if (newNode == null)
  66                 newNode = oldNode.ShallowClone(this.fac);
  67
  68             return base.Visit(newNode);
  69         }
  70
  71         /// <summary>
  72         /// Visit all children of "parent", replacing each child with a copy of each child.
  73         /// </summary>
  74         protected override QilNode VisitChildren(QilNode parent) {
  75             // Visit children
  76             for (int i = 0; i < parent.Count; i++) {
  77                 QilNode child = parent[i];
  78
  79                 // If child is a reference,
  80                 if (IsReference(parent, i)) {
  81                     // Visit the reference and substitute its copy
  82                     parent[i] = VisitReference(child);
  83
  84                     // If no substutition found, then use original child
  85                     if (parent[i] == null)
  86                         parent[i] = child;
  87                 }
  88                 else {
  89                     // Otherwise, visit the node and substitute its copy
  90                     parent[i] = Visit(child);
  91                 }
  92             }
  93
  94             return parent;
  95         }
  96
  97         /// <summary>
  98         /// If a cloned reference is in scope, replace "oldNode".  Otherwise, return "oldNode".
  99         /// </summary>
 100         protected override QilNode VisitReference(QilNode oldNode) {
 101             QilNode newNode = FindClonedReference(oldNode);
 102             return base.VisitReference(newNode == null ? oldNode : newNode);
 103         }
 104
 105
 106         //-----------------------------------------------
 107         // QilScopedVisitor methods
 108         //-----------------------------------------------
 109
 110         /// <summary>
 111         /// Push node and its shallow clone onto the substitution list.
 112         /// </summary>
 113         protected override void BeginScope(QilNode node) {
 114             this.subs.AddSubstitutionPair(node, node.ShallowClone(this.fac));
 115         }
 116
 117         /// <summary>
 118         /// Pop entry from substitution list.
 119         /// </summary>
 120         protected override void EndScope(QilNode node) {
 121             this.subs.RemoveLastSubstitutionPair();
 122         }
 123
 124
 125         //-----------------------------------------------
 126         // QilCloneVisitor methods
 127         //-----------------------------------------------
 128
 129         /// <summary>
 130         /// Find the clone of an in-scope reference.
 131         /// </summary>
 132         protected QilNode FindClonedReference(QilNode node) {
 133             return this.subs.FindReplacement(node);
 134         }
 135     }
 136 }