class/System/System.Collections.Specialized/HybridDictionary.cs

   1 //
   2 // System.Collections.Specialized.HybridDictionary.cs
   3 //
   4 // Author:
   5 //   Lawrence Pit (loz@cable.a2000.nl)
   6 //   Raja R Harinath <rharinath@novell.com>
   7 //
   8 // Copyright (C) 2004, 2005 Novell (http://www.novell.com)
   9 //
  10
  11 //
  12 // Permission is hereby granted, free of charge, to any person obtaining
  13 // a copy of this software and associated documentation files (the
  14 // "Software"), to deal in the Software without restriction, including
  15 // without limitation the rights to use, copy, modify, merge, publish,
  16 // distribute, sublicense, and/or sell copies of the Software, and to
  17 // permit persons to whom the Software is furnished to do so, subject to
  18 // the following conditions:
  19 //
  20 // The above copyright notice and this permission notice shall be
  21 // included in all copies or substantial portions of the Software.
  22 //
  23 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  27 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  28 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  29 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  30 //
  31
  32 namespace System.Collections.Specialized {
  33
  34         [Serializable]
  35         public class HybridDictionary : IDictionary, ICollection, IEnumerable {
  36
  37                 private const int switchAfter = 10;
  38
  39                 private IDictionary inner {
  40                         get { return list == null ? (IDictionary) hashtable : (IDictionary) list; }
  41                 }
  42
  43                 private bool caseInsensitive;
  44                 private Hashtable hashtable;
  45                 private ListDictionary list;
  46
  47                 // Constructors
  48
  49                 public HybridDictionary() : this (0, false) { }
  50
  51                 public HybridDictionary (bool caseInsensitive) : this (0, caseInsensitive) { }
  52
  53                 public HybridDictionary (int initialSize) : this (initialSize, false) { }
  54
  55                 public HybridDictionary (int initialSize, bool caseInsensitive)
  56                 {
  57                         this.caseInsensitive = caseInsensitive;
  58
  59                         IComparer comparer = caseInsensitive ? CaseInsensitiveComparer.DefaultInvariant : null;
  60                         IHashCodeProvider hcp = caseInsensitive ? CaseInsensitiveHashCodeProvider.DefaultInvariant : null;
  61
  62                         if (initialSize <= switchAfter)
  63                                 list = new ListDictionary (comparer);
  64                         else
  65                                 hashtable = new Hashtable (initialSize, hcp, comparer);
  66                 }
  67
  68                 // Properties
  69
  70                 public int Count {
  71                         get { return inner.Count; }
  72                 }
  73
  74                 public bool IsFixedSize {
  75                         get { return false; }
  76                 }
  77
  78                 public bool IsReadOnly {
  79                         get { return false; }
  80                 }
  81
  82                 public bool IsSynchronized {
  83                         get { return false; }
  84                 }
  85
  86                 public object this [object key] {
  87                         get { return inner [key]; }
  88
  89                         set {
  90                                 inner [key] = value;
  91                                 if (list != null && Count > switchAfter)
  92                                         Switch ();
  93                         }
  94                 }
  95
  96                 public ICollection Keys {
  97                         get { return inner.Keys; }
  98                 }
  99
 100                 public object SyncRoot {
 101                         get { return this; }
 102                 }
 103
 104                 public ICollection Values {
 105                         get { return inner.Values; }
 106                 }
 107
 108
 109                 // Methods
 110
 111                 public void Add (object key, object value)
 112                 {
 113                         inner.Add (key, value);
 114                         if (list != null && Count > switchAfter)
 115                                 Switch ();
 116                 }
 117
 118                 public void Clear ()
 119                 {
 120                         // According to MSDN, this doesn't switch a Hashtable back to a ListDictionary
 121                         inner.Clear ();
 122                 }
 123
 124                 public bool Contains (object key)
 125                 {
 126 #if NET_2_0
 127                         return inner.Contains (key);
 128 #else
 129                         // if the dictionary is empty, 'Contains (null)' doesn't throw an ArgumentNullException
 130                         return Count != 0 && inner.Contains (key);
 131 #endif
 132                 }
 133
 134                 public void CopyTo (Array array, int index)
 135                 {
 136                         inner.CopyTo (array, index);
 137                 }
 138
 139                 public IDictionaryEnumerator GetEnumerator ()
 140                 {
 141                         return inner.GetEnumerator ();
 142                 }
 143
 144                 IEnumerator IEnumerable.GetEnumerator ()
 145                 {
 146                         return GetEnumerator ();
 147                 }
 148
 149                 public void Remove (object key)
 150                 {
 151                         // According to MSDN, this does not switch a Hashtable back to a ListDictionary
 152                         // even if Count falls below switchAfter
 153                         inner.Remove (key);
 154                 }
 155
 156                 private void Switch ()
 157                 {
 158                         IComparer comparer = caseInsensitive ? CaseInsensitiveComparer.DefaultInvariant : null;
 159                         IHashCodeProvider hcp = caseInsensitive ? CaseInsensitiveHashCodeProvider.DefaultInvariant : null;
 160
 161                         hashtable = new Hashtable (list, hcp, comparer);
 162                         list.Clear ();
 163                         list = null;
 164                 }
 165         }
 166 }