mcs/class/referencesource/System.Xml/System/Xml/XPath/Internal/CacheOutputQuery.cs

   1 //------------------------------------------------------------------------------
   2 // <copyright file="CacheOutputQuery.cs" company="Microsoft">
   3 //     Copyright (c) Microsoft Corporation.  All rights reserved.
   4 // </copyright>
   5 // <owner current="true" primary="true">Microsoft</owner>
   6 //------------------------------------------------------------------------------
   7
   8 namespace MS.Internal.Xml.XPath {
   9     using System;
  10     using System.Xml;
  11     using System.Xml.XPath;
  12     using System.Diagnostics;
  13     using System.Xml.Xsl;
  14     using System.Collections.Generic;
  15
  16     internal abstract class CacheOutputQuery : Query {
  17         internal Query input;
  18         // int count; -- we reusing it here
  19         protected List<XPathNavigator> outputBuffer;
  20
  21         public CacheOutputQuery(Query input) {
  22             this.input = input;
  23             this.outputBuffer = new List<XPathNavigator>();
  24             this.count = 0;
  25         }
  26         protected CacheOutputQuery(CacheOutputQuery other) : base(other) {
  27             this.input        = Clone(other.input);
  28             this.outputBuffer = new List<XPathNavigator>(other.outputBuffer);
  29             this.count = other.count;
  30         }
  31
  32         public override void Reset() {
  33             this.count = 0;
  34         }
  35
  36         public override void SetXsltContext(XsltContext context){
  37             input.SetXsltContext(context);
  38         }
  39
  40         public override object Evaluate(XPathNodeIterator context) {
  41             outputBuffer.Clear();
  42             count = 0;
  43             return input.Evaluate(context);// This is trick. IDQuery needs this value. Otherwise we would return this.
  44                                             // All subclasses should and would anyway override thismethod and return this.
  45         }
  46
  47         public override XPathNavigator Advance() {
  48             Debug.Assert(0 <= count && count <= outputBuffer.Count);
  49             if (count < outputBuffer.Count) {
  50                 return outputBuffer[count++];
  51             }
  52             return null;
  53         }
  54
  55         public override XPathNavigator Current {
  56             get {
  57                 Debug.Assert(0 <= count && count <= outputBuffer.Count);
  58                 if (count == 0) {
  59                     return null;
  60                 }
  61                 return outputBuffer[count - 1];
  62             }
  63         }
  64
  65         public override XPathResultType StaticType { get { return XPathResultType.NodeSet; } }
  66         public override int CurrentPosition   { get { return count; } }
  67         public override int Count             { get { return outputBuffer.Count; } }
  68         public override QueryProps Properties { get { return QueryProps.Merge | QueryProps.Cached | QueryProps.Position | QueryProps.Count; } }
  69
  70         public override void PrintQuery(XmlWriter w) {
  71             w.WriteStartElement(this.GetType().Name);
  72             input.PrintQuery(w);
  73             w.WriteEndElement();
  74         }
  75     }
  76 }