mcs/class/System.Web/System.Web.Caching/ExpiresBuckets.cs

   1 // \r
   2 // System.Web.Caching\r
   3 //\r
   4 // Author:\r
   5 //   Patrik Torstensson (Patrik.Torstensson@labs2.com)\r
   6 //\r
   7 // (C) Copyright Patrik Torstensson, 2001\r
   8 //\r
   9 namespace System.Web.Caching\r
  10 {\r
  11         /// <summary>\r
  12         /// Responsible for holding a cache entry in the linked list bucket.\r
  13         /// </summary>\r
  14         public struct ExpiresEntry\r
  15         {\r
  16                 public CacheEntry       _objEntry;\r
  17                 public long                     _ticksExpires;\r
  18                 public int                      _intNext;\r
  19         }\r
  20 \r
  21         /// <summary>\r
  22         /// Holds cache entries that has a expiration in a bucket list.\r
  23         /// </summary>\r
  24         public class ExpiresBucket\r
  25         {\r
  26                 private static int MIN_ENTRIES = 16;\r
  27                 \r
  28                 private byte    _byteID;\r
  29                 private int             _intSize;\r
  30                 private int             _intCount;\r
  31                 private int             _intNext;\r
  32 \r
  33                 private Cache   _objManager;\r
  34 \r
  35                 private ExpiresEntry [] _arrEntries;\r
  36 \r
  37                 /// <summary>\r
  38                 /// Constructs a new bucket.\r
  39                 /// </summary>\r
  40                 /// <param name="bucket">Current bucket ID.</param>\r
  41                 /// <param name="objManager">Cache manager reponsible for the item(s) in the expires bucket.</param>\r
  42                 public ExpiresBucket(byte bucket, Cache objManager) \r
  43                 {\r
  44                         _objManager = objManager;\r
  45                         Initialize(bucket);\r
  46                 }\r
  47 \r
  48                 /// <summary>\r
  49                 /// Initializes the expires bucket, creates a linked list of MIN_ENTRIES.\r
  50                 /// </summary>\r
  51                 /// <param name="bucket">Bucket ID.</param>\r
  52                 private void Initialize(byte bucket)\r
  53                 {\r
  54                         _byteID = bucket;\r
  55                         _intNext = 0;\r
  56                         _intCount = 0;\r
  57 \r
  58                         _arrEntries = new ExpiresEntry[MIN_ENTRIES];\r
  59                         _intSize = MIN_ENTRIES;\r
  60 \r
  61                         int intPos = 0;\r
  62                         do \r
  63                         {\r
  64                                 _arrEntries[intPos]._intNext = intPos + 1;\r
  65                                 _arrEntries[intPos]._ticksExpires = System.DateTime.MaxValue.Ticks;\r
  66                                 \r
  67                                 intPos++;\r
  68                         } while (intPos < _intSize);\r
  69 \r
  70                         _arrEntries[_intSize - 1]._intNext = -1;\r
  71                 }\r
  72 \r
  73                 /// <summary>\r
  74                 /// Expands the bucket linked array list.\r
  75                 /// </summary>\r
  76                 private void Expand() \r
  77                 {\r
  78                         ExpiresEntry [] arrData;\r
  79                         int intPos = 0;\r
  80                         int intOldSize;\r
  81 \r
  82                         lock(this)      \r
  83                         {\r
  84                                 intOldSize = _intSize;\r
  85                                 _intSize *= 2;\r
  86 \r
  87                                 // Create a new array and copy the old data into the new array\r
  88                                 arrData = new ExpiresEntry[_intSize];\r
  89                                 do \r
  90                                 {\r
  91                                         arrData[intPos] = _arrEntries[intPos];\r
  92                                         intPos++;\r
  93                                 } while (intPos < intOldSize);\r
  94 \r
  95                                 _intNext = intPos;\r
  96 \r
  97                                 // Initialize the "new" positions.\r
  98                                 do \r
  99                                 {\r
 100                                         arrData[intPos]._intNext = intPos + 1;\r
 101                                         intPos++;\r
 102                                 } while (intPos < _intSize);\r
 103 \r
 104                                 arrData[_intSize - 1]._intNext = -1;\r
 105 \r
 106                                 _arrEntries = arrData;\r
 107                         }\r
 108                 }\r
 109 \r
 110                 /// <summary>\r
 111                 /// Adds a cache entry into the expires bucket.\r
 112                 /// </summary>\r
 113                 /// <param name="objEntry">Cache Entry object to be added.</param>\r
 114                 public void Add(CacheEntry objEntry)\r
 115                 {\r
 116                         if (_intNext == -1) \r
 117                         {\r
 118                                 Expand();\r
 119                         }\r
 120                         \r
 121                         lock(this)      \r
 122                         {\r
 123                                 _arrEntries[_intNext]._ticksExpires =  objEntry.Expires;\r
 124                                 _arrEntries[_intNext]._objEntry = objEntry;\r
 125 \r
 126                                 _intNext = _arrEntries[_intNext]._intNext;\r
 127                         \r
 128                                 _intCount++;\r
 129                         }\r
 130                 }\r
 131 \r
 132                 /// <summary>\r
 133                 /// Removes a cache entry from the expires bucket.\r
 134                 /// </summary>\r
 135                 /// <param name="objEntry">Cache entry to be removed.</param>\r
 136                 public void Remove(CacheEntry objEntry)\r
 137                 {\r
 138                         lock(this)\r
 139                         {\r
 140                                 // Check if this is our bucket\r
 141                                 if (objEntry.ExpiresIndex != _byteID) return;\r
 142                                 if (objEntry.ExpiresIndex == System.Int32.MaxValue) return;\r
 143                                 if (_arrEntries.Length < objEntry.ExpiresIndex) return;\r
 144 \r
 145                                 _intCount--;\r
 146 \r
 147                                 _arrEntries[objEntry.ExpiresIndex]._objEntry.ExpiresBucket = byte.MaxValue;\r
 148                                 _arrEntries[objEntry.ExpiresIndex]._objEntry.ExpiresIndex = int.MaxValue;\r
 149                                 _arrEntries[objEntry.ExpiresIndex]._objEntry = null;\r
 150                                 _intNext = _arrEntries[objEntry.ExpiresIndex]._intNext;\r
 151                         }                       \r
 152                 }\r
 153 \r
 154                 /// <summary>\r
 155                 /// Updates a cache entry in the expires bucket, this is called during a hit of an item if the \r
 156                 /// cache item has a sliding expiration. The function is responsible for updating the cache\r
 157                 /// entry.\r
 158                 /// </summary>\r
 159                 /// <param name="objEntry">Cache entry to update.</param>\r
 160                 /// <param name="ticksExpires">New expiration value for the cache entry.</param>\r
 161                 public void Update(CacheEntry objEntry, long ticksExpires)\r
 162                 {\r
 163                         lock(this)\r
 164                         {\r
 165                                 // Check if this is our bucket\r
 166                                 if (objEntry.ExpiresIndex != _byteID) return;\r
 167                                 if (objEntry.ExpiresIndex == System.Int32.MaxValue) return;\r
 168                                 if (_arrEntries.Length < objEntry.ExpiresIndex) return;\r
 169 \r
 170                                 _arrEntries[objEntry.ExpiresIndex]._ticksExpires = ticksExpires;\r
 171                                 _arrEntries[objEntry.ExpiresIndex]._objEntry.Expires = ticksExpires;\r
 172                         }\r
 173                 }\r
 174 \r
 175                 /// <summary>\r
 176                 /// Flushes all cache entries that has expired and removes them from the cache manager.\r
 177                 /// </summary>\r
 178                 public void FlushExpiredItems()\r
 179                 {\r
 180                         ExpiresEntry objEntry;\r
 181                         CacheEntry [] arrCacheEntries;\r
 182                         \r
 183                         int             intCachePos;\r
 184                         int             intPos;\r
 185                         long    ticksNow;\r
 186         \r
 187                         ticksNow = System.DateTime.Now.Ticks;\r
 188 \r
 189                         intCachePos = 0;\r
 190 \r
 191                         // Lookup all items that needs to be removed, this is done in a two part\r
 192                         // operation to minimize the locking time.\r
 193                         lock (this)\r
 194                         {\r
 195                                 arrCacheEntries = new CacheEntry[_intSize];\r
 196 \r
 197                                 intPos = 0;\r
 198                                 do \r
 199                                 {\r
 200                                         objEntry = _arrEntries[intPos];\r
 201                                         if (objEntry._objEntry != null)\r
 202                                         {\r
 203                                                 if (objEntry._ticksExpires < ticksNow)\r
 204                                                 {\r
 205                                                         arrCacheEntries[intCachePos++] = objEntry._objEntry;\r
 206 \r
 207                                                         objEntry._objEntry.ExpiresBucket = byte.MaxValue;\r
 208                                                         objEntry._objEntry.ExpiresIndex = int.MaxValue;\r
 209                                                         objEntry._objEntry = null;\r
 210                                                         _intNext = objEntry._intNext;\r
 211                                                 }\r
 212                                         }\r
 213                                         \r
 214                                         intPos++;\r
 215                                 } while (intPos < _intSize);\r
 216                         }\r
 217 \r
 218                         // If we have any entries to remove, go ahead and call the cache manager remove.\r
 219                         if (intCachePos > 0)\r
 220                         {\r
 221                                 intPos = 0;\r
 222                                 do \r
 223                                 {\r
 224                                         _objManager.Remove(arrCacheEntries[intPos].Key, CacheItemRemovedReason.Expired);\r
 225 \r
 226                                         intPos++;\r
 227                                 } while (intPos < intCachePos);\r
 228                         }\r
 229                 }\r
 230 \r
 231                 /// <summary>\r
 232                 /// Returns the current size of the expires bucket.\r
 233                 /// </summary>\r
 234                 public int Size\r
 235                 {\r
 236                         get \r
 237                         { \r
 238                                 return _arrEntries.Length;\r
 239                         }\r
 240                 }\r
 241 \r
 242                 /// <summary>\r
 243                 /// Returns number of items in the bucket.\r
 244                 /// </summary>\r
 245                 public int Count\r
 246                 {\r
 247                         get \r
 248                         {\r
 249                                 return  _intCount;\r
 250                         }\r
 251                 }\r
 252         }\r
 253 }\r