mcs/class/System/System.Text.RegularExpressions/cache.cs

   1 //\r
   2 // assembly:    System\r
   3 // namespace:   System.Text.RegularExpressions\r
   4 // file:        cache.cs\r
   5 //\r
   6 // author:      Dan Lewis (dlewis@gmx.co.uk)\r
   7 //              (c) 2002\r
   8
   9 //
  10 // Permission is hereby granted, free of charge, to any person obtaining
  11 // a copy of this software and associated documentation files (the
  12 // "Software"), to deal in the Software without restriction, including
  13 // without limitation the rights to use, copy, modify, merge, publish,
  14 // distribute, sublicense, and/or sell copies of the Software, and to
  15 // permit persons to whom the Software is furnished to do so, subject to
  16 // the following conditions:
  17 //
  18 // The above copyright notice and this permission notice shall be
  19 // included in all copies or substantial portions of the Software.
  20 //
  21 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  22 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  23 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  24 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  25 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  26 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  27 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  28 //
  29 \r
  30 using System;\r
  31 using System.Collections;\r
  32 \r
  33 namespace System.Text.RegularExpressions {\r
  34 \r
  35         class FactoryCache {\r
  36                 public FactoryCache (int capacity) {\r
  37                         this.capacity = capacity;\r
  38                         this.factories = new Hashtable (capacity);\r
  39                         this.mru_list = new MRUList ();\r
  40                 }\r
  41 \r
  42                 public void Add (string pattern, RegexOptions options, IMachineFactory factory) {\r
  43                         lock (this) {\r
  44                                 Key k = new Key (pattern, options);\r
  45 \r
  46                                 while (factories.Count >= capacity) {\r
  47                                         object victim = mru_list.Evict ();\r
  48                                         if (victim != null)\r
  49                                                 factories.Remove ((Key)victim);\r
  50                                 }\r
  51                                 \r
  52                                 factories[k] = factory;\r
  53                                 mru_list.Use (k);\r
  54                         }\r
  55                 }\r
  56 \r
  57                 public IMachineFactory Lookup (string pattern, RegexOptions options) {\r
  58                         lock (this) {\r
  59                                 Key k = new Key (pattern, options);\r
  60                                 if (factories.Contains (k)) {\r
  61                                         mru_list.Use (k);\r
  62                                         return (IMachineFactory)factories[k];\r
  63                                 }\r
  64                         }\r
  65 \r
  66                         return null;\r
  67                 }\r
  68 \r
  69                 private int capacity;\r
  70                 private Hashtable factories;\r
  71                 private MRUList mru_list;\r
  72 \r
  73                 class Key {\r
  74                         public string pattern;\r
  75                         public RegexOptions options;\r
  76 \r
  77                         public Key (string pattern, RegexOptions options) {\r
  78                                 this.pattern = pattern;\r
  79                                 this.options = options;\r
  80                         }\r
  81                         \r
  82                         public override int GetHashCode () {\r
  83                                 return pattern.GetHashCode () ^ (int)options;\r
  84                         }\r
  85 \r
  86                         public override bool Equals (object o) {\r
  87                                 if (o == null || !(o is Key))\r
  88                                         return false;\r
  89 \r
  90                                 Key k = (Key)o;\r
  91                                 return options == k.options && pattern.Equals (k.pattern);\r
  92                         }\r
  93 \r
  94                         public override string ToString () {\r
  95                                 return "('" + pattern + "', [" + options + "])";\r
  96                         }\r
  97                 }\r
  98         }\r
  99 \r
 100         class MRUList {\r
 101                 public MRUList () {\r
 102                         head = tail = null;\r
 103                 }\r
 104 \r
 105                 public void Use (object o) {\r
 106                         Node node;\r
 107 \r
 108                         if (head == null) {\r
 109                                 node = new Node (o);\r
 110                                 head = tail = node;\r
 111                                 return;\r
 112                         }\r
 113 \r
 114                         node = head;\r
 115                         while (node != null && !o.Equals (node.value))\r
 116                                 node = node.previous;\r
 117 \r
 118                         if (node == null)\r
 119                                 node = new Node (o);\r
 120                         else {\r
 121                                 if (node == head)\r
 122                                         return;\r
 123 \r
 124                                 if (node == tail)\r
 125                                         tail = node.next;\r
 126                                 else\r
 127                                         node.previous.next = node.next;\r
 128 \r
 129                                 node.next.previous = node.previous;\r
 130                         }\r
 131 \r
 132                         head.next = node;\r
 133                         node.previous = head;\r
 134                         node.next = null;\r
 135                         head = node;\r
 136                 }\r
 137 \r
 138                 public object Evict () {\r
 139                         if (tail == null)\r
 140                                 return null;\r
 141 \r
 142                         object o = tail.value;\r
 143                         tail = tail.next;\r
 144 \r
 145                         if (tail == null)\r
 146                                 head = null;\r
 147                         else\r
 148                                 tail.previous = null;\r
 149 \r
 150                         return o;\r
 151                 }\r
 152 \r
 153                 private Node head, tail;\r
 154 \r
 155                 private class Node {\r
 156                         public object value;\r
 157                         public Node previous, next;\r
 158 \r
 159                         public Node (object value) {\r
 160                                 this.value = value;\r
 161                         }\r
 162                 }\r
 163         }\r
 164 }\r