Unified ImageFileCache implementations

MapControl/Shared/ImageFileCache.cs

@@ -5,7 +5,9 @@
 using System;
 using System.Diagnostics;
 using System.IO;
+using System.Linq;
 using System.Text;
+using System.Threading.Tasks;
 
 namespace MapControl.Caching
 {
@@ -30,6 +32,11 @@ namespace MapControl.Caching
             Debug.WriteLine("Created ImageFileCache in " + rootDirectory);
         }
 
+        public Task Clean()
+        {
+            return Task.Factory.StartNew(CleanRootDirectory, TaskCreationOptions.LongRunning);
+        }
+
         private string GetPath(string key)
         {
             try
@@ -44,6 +51,81 @@ namespace MapControl.Caching
             return null;
         }
 
+        private void CleanRootDirectory()
+        {
+            foreach (var dir in new DirectoryInfo(rootDirectory).EnumerateDirectories())
+            {
+                var deletedFileCount = CleanDirectory(dir);
+
+                if (deletedFileCount > 0)
+                {
+                    Debug.WriteLine("ImageFileCache: Cleaned {0} files in {1}", deletedFileCount, dir);
+                }
+            }
+        }
+
+        private static int CleanDirectory(DirectoryInfo directory)
+        {
+            var deletedFileCount = 0;
+
+            foreach (var dir in directory.EnumerateDirectories())
+            {
+                deletedFileCount += CleanDirectory(dir);
+            }
+
+            foreach (var file in directory.EnumerateFiles())
+            {
+                try
+                {
+                    if (ReadExpiration(file) < DateTime.UtcNow)
+                    {
+                        file.Delete();
+                        deletedFileCount++;
+                    }
+                }
+                catch (Exception ex)
+                {
+                    Debug.WriteLine("ImageFileCache: Failed cleaning {0}: {1}", file.FullName, ex.Message);
+                }
+            }
+
+            if (!directory.EnumerateFileSystemInfos().Any())
+            {
+                try
+                {
+                    directory.Delete();
+                }
+                catch (Exception ex)
+                {
+                    Debug.WriteLine("ImageFileCache: Failed cleaning {0}: {1}", directory.FullName, ex.Message);
+                }
+            }
+
+            return deletedFileCount;
+        }
+
+        private static DateTime ReadExpiration(FileInfo file)
+        {
+            DateTime? expiration = null;
+
+            if (file.Length > 16)
+            {
+                var buffer = new byte[16];
+
+                using (var stream = file.OpenRead())
+                {
+                    stream.Seek(-16, SeekOrigin.End);
+
+                    if (stream.Read(buffer, 0, 16) == 16)
+                    {
+                        expiration = ReadExpiration(buffer);
+                    }
+                }
+            }
+
+            return expiration ?? DateTime.Today;
+        }
+
         private static DateTime ReadExpiration(ref byte[] buffer)
         {
             DateTime? expiration = ReadExpiration(buffer);
@@ -59,13 +141,15 @@ namespace MapControl.Caching
 
         private static DateTime? ReadExpiration(byte[] buffer)
         {
+            DateTime? expiration = null;
+
             if (buffer.Length >= 16 &&
                 Encoding.ASCII.GetString(buffer, buffer.Length - 16, 8) == expiresTag)
             {
-                return new DateTime(BitConverter.ToInt64(buffer, buffer.Length - 8), DateTimeKind.Utc);
+                expiration = new DateTime(BitConverter.ToInt64(buffer, buffer.Length - 8), DateTimeKind.Utc);
             }
 
-            return null;
+            return expiration;
         }
     }
 }