[WorldWind学习]8.Cache对象

// set Upper and Lower limits for Cache size control, in bytes
                long CacheUpperLimit = (long)Settings.CacheSizeMegaBytes * 1024L * 1024L;
                long CacheLowerLimit = (long)Settings.CacheSizeMegaBytes * 768L * 1024L;    //75% of upper limit
                //Set up the cache
                worldWindow.Cache = new Cache(
                    Settings.CachePath,
                    CacheLowerLimit,
                    CacheUpperLimit,
                    Settings.CacheCleanupInterval, 
                    Settings.TotalRunTime );

public static WorldWindSettings Settings = new WorldWindSettings();

// ParseArgs may set values that are used elsewhere,
// such as startFullScreen and CurrentSettingsDirectory.
ParseArgs(args);
if(CurrentSettingsDirectory == null)
{
      // load program settings from default directory
      LoadSettings();    
      World.LoadSettings();
}
else
{
    LoadSettings(CurrentSettingsDirectory);
    World.LoadSettings(CurrentSettingsDirectory);
}

 1 /// <summary>
 2         /// Initializes a new instance of the <see cref= "T:WorldWind.Cache"/> class.
 3         /// </summary>
 4         /// <param name="cacheDirectory">Location of the cache files.</param>
 5         /// <param name="cleanupFrequencyInterval">Frequency of cache cleanup.</param>
 6         /// <param name="totalRunTime">Total duration application has been running so far.</param>
 7         public Cache(
 8             string cacheDirectory,
 9             TimeSpan cleanupFrequencyInterval,
10             TimeSpan totalRunTime)
11         {
12             this.CleanupFrequency = cleanupFrequencyInterval;
13             this.CacheDirectory = cacheDirectory;
14             Directory.CreateDirectory(this.CacheDirectory);
15 
16             // Start the timer
17             double firstDueSeconds = cleanupFrequencyInterval.TotalSeconds - 
18                 totalRunTime.TotalSeconds % cleanupFrequencyInterval.TotalSeconds;
19             m_timer = new Timer( new TimerCallback(OnTimer), null,
20                 (long)(firstDueSeconds*1000),
21                 (long)cleanupFrequencyInterval.TotalMilliseconds );
22         }
23 
24         /// <summary>
25         /// Constructor.
26         /// </summary>
27         /// <param name="cacheDirectory">Location of the cache files.</param>
28         /// <param name="cleanupFrequencyInterval">Frequency of cache cleanup.</param>
29         /// <param name="totalRunTime">Total duration application has been running so far.</param>
30         public Cache(
31             string cacheDirectory,
32             long cacheLowerLimit,
33             long cacheUpperLimit,
34             TimeSpan cleanupFrequencyInterval,
35             TimeSpan totalRunTime)
36             : this(cacheDirectory, cleanupFrequencyInterval, totalRunTime )
37         {
38             this.CacheLowerLimit = cacheLowerLimit;
39             this.CacheUpperLimit = cacheUpperLimit;
40         }

 1 /// <summary>
 2         /// Monitors the cache, makes sure it stays within limits.
 3         /// </summary>
 4         private void OnTimer(object state)
 5         {
 6             try
 7             {
 8                 // We are are not in a hurry
 9                 Thread.CurrentThread.Priority = ThreadPriority.BelowNormal;
10 
11                 // dirSize is reported as the total of the file sizes, in bytes
12                 // TODO: use the on-disk filesize, not FileInfo.Length, to calculate dirSize
13                 long dirSize = GetDirectorySize(new DirectoryInfo(this.CacheDirectory));//dirSize是缓存文件夹的大小
14                 if(dirSize < this.CacheUpperLimit)//小于限定值不清理
15                     return;
16 
17                 ArrayList fileInfoList = GetDirectoryFileInfoList(new DirectoryInfo(this.CacheDirectory));
18                 while(dirSize > this.CacheLowerLimit)
19                 {
20                     if (fileInfoList.Count <= 100)
21                         break;
22 
23                     FileInfo oldestFile = null;
24                     foreach(FileInfo curFile in fileInfoList)
25                     {
26                         if(oldestFile == null)
27                         {
28                             oldestFile = curFile;
29                             continue;
30                         }
31 
32                         if(curFile.LastAccessTimeUtc < oldestFile.LastAccessTimeUtc)
33                         {
34                             oldestFile = curFile;
35                         }
36                     }
37 
38                     fileInfoList.Remove(oldestFile);
39                     dirSize -= oldestFile.Length;
40                     try
41                     {
42                         File.Delete(oldestFile.FullName);
43 
44                         // Recursively remove empty directories
45                         string directory = oldestFile.Directory.FullName;
46                         while(Directory.GetFileSystemEntries(directory).Length==0)
47                         {
48                             Directory.Delete(directory);
49                             directory = Path.GetDirectoryName(directory);
50                         }
51                     }
52                     catch(IOException)
53                     {
54                         // Ignore non-removable file - move on to next
55                     }
56                 }
57             }
58             catch(Exception caught)
59             {
60                 Log.Write(Log.Levels.Error, "CACH", caught.Message);
61             }
62         }