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 \r
   9 using System;\r
  10 using System.Collections;\r
  11 \r
  12 namespace System.Text.RegularExpressions {\r
  13 \r
  14         class FactoryCache {\r
  15                 public FactoryCache (int capacity) {\r
  16                         this.capacity = capacity;\r
  17                         this.factories = new Hashtable (capacity);\r
  18                         this.mru_list = new MRUList ();\r
  19                 }\r
  20 \r
  21                 public void Add (string pattern, RegexOptions options, IMachineFactory factory) {\r
  22                         lock (this) {\r
  23                                 Key k = new Key (pattern, options);\r
  24 \r
  25                                 while (factories.Count >= capacity) {\r
  26                                         object victim = mru_list.Evict ();\r
  27                                         if (victim != null)\r
  28                                                 factories.Remove ((Key)victim);\r
  29                                 }\r
  30                                 \r
  31                                 factories[k] = factory;\r
  32                                 mru_list.Use (k);\r
  33                         }\r
  34                 }\r
  35 \r
  36                 public IMachineFactory Lookup (string pattern, RegexOptions options) {\r
  37                         lock (this) {\r
  38                                 Key k = new Key (pattern, options);\r
  39                                 if (factories.Contains (k)) {\r
  40                                         mru_list.Use (k);\r
  41                                         return (IMachineFactory)factories[k];\r
  42                                 }\r
  43                         }\r
  44 \r
  45                         return null;\r
  46                 }\r
  47 \r
  48                 private int capacity;\r
  49                 private Hashtable factories;\r
  50                 private MRUList mru_list;\r
  51 \r
  52                 class Key {\r
  53                         public string pattern;\r
  54                         public RegexOptions options;\r
  55 \r
  56                         public Key (string pattern, RegexOptions options) {\r
  57                                 this.pattern = pattern;\r
  58                                 this.options = options;\r
  59                         }\r
  60                         \r
  61                         public override int GetHashCode () {\r
  62                                 return pattern.GetHashCode () ^ (int)options;\r
  63                         }\r
  64 \r
  65                         public override bool Equals (object o) {\r
  66                                 if (o == null || !(o is Key))\r
  67                                         return false;\r
  68 \r
  69                                 Key k = (Key)o;\r
  70                                 return options == k.options && pattern.Equals (k.pattern);\r
  71                         }\r
  72 \r
  73                         public override string ToString () {\r
  74                                 return "('" + pattern + "', [" + options + "])";\r
  75                         }\r
  76                 }\r
  77         }\r
  78 \r
  79         class MRUList {\r
  80                 public MRUList () {\r
  81                         head = tail = null;\r
  82                 }\r
  83 \r
  84                 public void Use (object o) {\r
  85                         Node node;\r
  86 \r
  87                         if (head == null) {\r
  88                                 node = new Node (o);\r
  89                                 head = tail = node;\r
  90                                 return;\r
  91                         }\r
  92 \r
  93                         node = head;\r
  94                         while (node != null && !o.Equals (node.value))\r
  95                                 node = node.previous;\r
  96 \r
  97                         if (node == null)\r
  98                                 node = new Node (o);\r
  99                         else {\r
 100                                 if (node == head)\r
 101                                         return;\r
 102 \r
 103                                 if (node == tail)\r
 104                                         tail = node.next;\r
 105                                 else\r
 106                                         node.previous.next = node.next;\r
 107 \r
 108                                 node.next.previous = node.previous;\r
 109                         }\r
 110 \r
 111                         head.next = node;\r
 112                         node.previous = head;\r
 113                         node.next = null;\r
 114                         head = node;\r
 115                 }\r
 116 \r
 117                 public object Evict () {\r
 118                         if (tail == null)\r
 119                                 return null;\r
 120 \r
 121                         object o = tail.value;\r
 122                         tail = tail.next;\r
 123 \r
 124                         if (tail == null)\r
 125                                 head = null;\r
 126                         else\r
 127                                 tail.previous = null;\r
 128 \r
 129                         return o;\r
 130                 }\r
 131 \r
 132                 private Node head, tail;\r
 133 \r
 134                 private class Node {\r
 135                         public object value;\r
 136                         public Node previous, next;\r
 137 \r
 138                         public Node (object value) {\r
 139                                 this.value = value;\r
 140                         }\r
 141                 }\r
 142         }\r
 143 }\r