mcs/class/referencesource/System.Xml/System/Xml/HWStack.cs

   1 //------------------------------------------------------------------------------
   2 // <copyright file="HWStack.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
  10
  11 namespace System.Xml {
  12
  13 // This stack is designed to minimize object creation for the
  14 // objects being stored in the stack by allowing them to be
  15 // re-used over time.  It basically pushes the objects creating
  16 // a high water mark then as Pop() is called they are not removed
  17 // so that next time Push() is called it simply returns the last
  18 // object that was already on the stack.
  19
  20     internal class HWStack : ICloneable {
  21         internal HWStack(int GrowthRate) : this (GrowthRate, int.MaxValue) {}
  22
  23         internal HWStack(int GrowthRate, int limit) {
  24             this.growthRate = GrowthRate;
  25             this.used = 0;
  26             this.stack = new Object[GrowthRate];
  27             this.size = GrowthRate;
  28             this.limit = limit;
  29         }
  30
  31         internal Object Push() {
  32             if (this.used == this.size) {
  33                 if (this.limit <= this.used) {
  34                     throw new XmlException(Res.Xml_StackOverflow, string.Empty);
  35                 }
  36                 Object[] newstack = new Object[this.size + this.growthRate];
  37                 if (this.used > 0) {
  38                     System.Array.Copy(this.stack, 0, newstack, 0, this.used);
  39                 }
  40                 this.stack = newstack;
  41                 this.size += this.growthRate;
  42             }
  43             return this.stack[this.used++];
  44         }
  45
  46         internal Object Pop() {
  47             if (0 < this.used) {
  48                 this.used--;
  49                 Object result = this.stack[this.used];
  50                 return result;
  51             }
  52             return null;
  53         }
  54
  55         internal object Peek() {
  56             return this.used > 0 ? this.stack[this.used - 1] : null;
  57         }
  58
  59         internal void AddToTop(object o) {
  60             if (this.used > 0) {
  61                 this.stack[this.used - 1] = o;
  62             }
  63         }
  64
  65         internal Object this[int index] {
  66             get {
  67                 if (index >= 0 && index < this.used) {
  68                     Object result = this.stack[index];
  69                     return result;
  70                 }
  71                 else {
  72                                         throw new IndexOutOfRangeException();
  73                                 }
  74             }
  75             set {
  76                 if (index >= 0 && index < this.used) {
  77                                         this.stack[index] = value;
  78                                 }
  79                 else {
  80                                         throw new IndexOutOfRangeException();
  81                                 }
  82             }
  83         }
  84
  85         internal int Length {
  86             get { return this.used;}
  87         }
  88
  89         //
  90         // ICloneable
  91         //
  92
  93         private HWStack(object[] stack, int growthRate, int used, int size) {
  94             this.stack      = stack;
  95             this.growthRate = growthRate;
  96             this.used       = used;
  97             this.size       = size;
  98         }
  99
 100         public object Clone() {
 101             return new HWStack((object[]) this.stack.Clone(), this.growthRate, this.used, this.size);
 102         }
 103
 104         private Object[] stack;
 105         private int growthRate;
 106         private int used;
 107         private int size;
 108         private int limit;
 109     };
 110
 111 }