mcs/class/Npgsql/Npgsql/Cache.cs

   1 // created on 29/11/2007\r
   2 \r
   3 // Npgsql.NpgsqlConnectionStringBuilder.cs\r
   4 //\r
   5 // Author:\r
   6 //      Glen Parker (glenebob@nwlink.com)\r
   7 //      Ben Sagal (bensagal@gmail.com)\r
   8 //      Tao Wang (dancefire@gmail.com)\r
   9 //\r
  10 //      Copyright (C) 2007 The Npgsql Development Team\r
  11 //      npgsql-general@gborg.postgresql.org\r
  12 //      http://gborg.postgresql.org/project/npgsql/projdisplay.php\r
  13 //\r
  14 // Permission to use, copy, modify, and distribute this software and its\r
  15 // documentation for any purpose, without fee, and without a written\r
  16 // agreement is hereby granted, provided that the above copyright notice\r
  17 // and this paragraph and the following two paragraphs appear in all copies.\r
  18 // \r
  19 // IN NO EVENT SHALL THE NPGSQL DEVELOPMENT TEAM BE LIABLE TO ANY PARTY\r
  20 // FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES,\r
  21 // INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS\r
  22 // DOCUMENTATION, EVEN IF THE NPGSQL DEVELOPMENT TEAM HAS BEEN ADVISED OF\r
  23 // THE POSSIBILITY OF SUCH DAMAGE.\r
  24 // \r
  25 // THE NPGSQL DEVELOPMENT TEAM SPECIFICALLY DISCLAIMS ANY WARRANTIES,\r
  26 // INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY\r
  27 // AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS\r
  28 // ON AN "AS IS" BASIS, AND THE NPGSQL DEVELOPMENT TEAM HAS NO OBLIGATIONS\r
  29 // TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.\r
  30 \r
  31 using System;\r
  32 using System.Collections.Generic;\r
  33 //using System.Text;\r
  34 \r
  35 namespace Npgsql\r
  36 {\r
  37         internal class Cache<TEntity> : LinkedList<KeyValuePair<string, TEntity>>\r
  38                 where TEntity : class\r
  39         {\r
  40                 private int _cache_size = 20;\r
  41 \r
  42                 /// <summary>\r
  43                 /// Set Cache Size. The default value is 20.\r
  44                 /// </summary>\r
  45                 public int CacheSize\r
  46                 {\r
  47                         get { return _cache_size; }\r
  48                         set\r
  49                         {\r
  50                                 if (value < 0) { throw new ArgumentOutOfRangeException("CacheSize"); }\r
  51 \r
  52                                 _cache_size = value;\r
  53 \r
  54                                 if (this.Count > _cache_size)\r
  55                                 {\r
  56                                         lock (this)\r
  57                                         {\r
  58                                                 while (_cache_size < this.Count)\r
  59                                                 {\r
  60                                                         RemoveLast();\r
  61                                                 }\r
  62                                         }\r
  63                                 }\r
  64                         }\r
  65                 }\r
  66 \r
  67                 /// <summary>\r
  68                 /// Lookup cached entity. null will returned if not match.\r
  69                 /// For both get{} and set{} apply LRU rule.\r
  70                 /// </summary>\r
  71                 /// <param name="key">key</param>\r
  72                 /// <returns></returns>\r
  73                 public TEntity this[string key]\r
  74                 {\r
  75                         get\r
  76                         {\r
  77                                 lock (this)\r
  78                                 {\r
  79                                         for (LinkedListNode<KeyValuePair<string, TEntity>> node = this.First; node != null; node = node.Next)\r
  80                                         {\r
  81                                                 if (node.Value.Key == key)\r
  82                                                 {\r
  83                                                         this.Remove(node);\r
  84                                                         this.AddFirst(node);\r
  85                                                         return node.Value.Value;\r
  86                                                 }\r
  87                                         }\r
  88                                 }\r
  89                                 return null;\r
  90                         }\r
  91                         set\r
  92                         {\r
  93                                 lock (this)\r
  94                                 {\r
  95                                         for (LinkedListNode<KeyValuePair<string, TEntity>> node = this.First; node != null; node = node.Next)\r
  96                                         {\r
  97                                                 if (node.Value.Key == key)\r
  98                                                 {\r
  99                                                         this.Remove(node);\r
 100                                                         this.AddFirst(node);\r
 101                                                         return;\r
 102                                                 }\r
 103                                         }\r
 104                                         if (this.CacheSize > 0)\r
 105                                         {\r
 106                                                 this.AddFirst(new KeyValuePair<string, TEntity>(key, value));\r
 107                                                 if (this.Count > this.CacheSize)\r
 108                                                 {\r
 109                                                         this.RemoveLast();\r
 110                                                 }\r
 111                                         }\r
 112                                 }\r
 113                         }\r
 114                 }\r
 115 \r
 116                 public Cache() : base() { }\r
 117                 public Cache(int cacheSize) : base()\r
 118                 {\r
 119                         this._cache_size = cacheSize;\r
 120                 }\r
 121         }\r
 122 }\r