Changeset 2156 for trunk/eraser/Eraser.DefaultPlugins/FileSystems/Windows.cs

Timestamp:

6/13/2010 12:39:53 AM (2 years ago)

Author:

lowjoel

Message:

• Optimised the EraseFileClusterTips? and GetFileArea? function to use one StreamInfo? object per file. This reduces the overhead associated with creating StreamInfos?.
• Minor code restructuring in EraseFileClusterTips? to use one try-finally instead of a try-finally within a using (which does the same thing)
• Removed one try-finally block in EraseClusterTips? when setting file attributes and moved it to EraseFileClusterTips? instead, combining one try-finally block.
• Handle ArgumentExceptions? from the FileSystemInfo?.Attributes.set setter as UnauthorizedAccessExceptions?.

File:

• trunk/eraser/Eraser.DefaultPlugins/FileSystems/Windows.cs (modified) (4 diffs)

trunk/eraser/Eraser.DefaultPlugins/FileSystems/Windows.cs

@@ -223 +223 @@
                 try
                 {
-                    //Reset the file attributes.
-                    FileAttributes fileAttr = streamInfo.Attributes;
-                    streamInfo.Attributes = FileAttributes.Normal;
-
-                    try
-                    {
-                        EraseFileClusterTips(files[i], method);
-                    }
-                    finally
-                    {
-                        streamInfo.Attributes = fileAttr;
-                    }
+                    EraseFileClusterTips(streamInfo, method);
                 }
                 catch (UnauthorizedAccessException)
@@ -325 +314 @@
         /// Erases the cluster tips of the given file.
         /// </summary>
-        /// <param name="file">The file to erase.</param>
+        /// <param name="stream">The stream to erase.</param>
         /// <param name="method">The erasure method to use.</param>
-        private void EraseFileClusterTips(string file, ErasureMethod method)
+        private void EraseFileClusterTips(StreamInfo streamInfo, ErasureMethod method)
         {
             //Get the file access times
-            StreamInfo streamInfo = new StreamInfo(file);
             DateTime lastAccess = streamInfo.LastAccessTime;
             DateTime lastWrite = streamInfo.LastWriteTime;
             DateTime created = streamInfo.CreationTime;
 
+            //Get the file attributes
+            FileAttributes attributes = streamInfo.Attributes;
+
             //And get the file lengths to know how much to overwrite
-            long fileArea = GetFileArea(file);
+            long fileArea = GetFileArea(streamInfo);
             long fileLength = streamInfo.Length;
 
@@ -343 +334 @@
                 return;
 
-            //Otherwise, create the stream, lengthen the file, then tell the erasure
-            //method to erase the cluster tips.
+            //Otherwise, unset any read-only flags, create the stream, lengthen the
+            //file, then tell the erasure method to erase the cluster tips.
             try
             {
-                using (FileStream stream = streamInfo.Open(FileMode.Open, FileAccess.Write,
-                    FileShare.None, FileOptions.WriteThrough))
-                {
-                    try
-                    {
-                        stream.SetLength(fileArea);
-                        stream.Seek(fileLength, SeekOrigin.Begin);
-
-                        //Erase the file
-                        method.Erase(stream, long.MaxValue,
-                            ManagerLibrary.Instance.PrngRegistrar[
-                                ManagerLibrary.Settings.ActivePrng],
-                            null);
-                    }
-                    finally
-                    {
-                        //Make sure the file length is restored!
-                        stream.SetLength(fileLength);
-                    }
-                }
+                streamInfo.Attributes = FileAttributes.Normal;
+                FileStream stream = streamInfo.Open(FileMode.Open, FileAccess.Write,
+                    FileShare.None, FileOptions.WriteThrough);
+
+                try
+                {
+                    stream.SetLength(fileArea);
+                    stream.Seek(fileLength, SeekOrigin.Begin);
+
+                    //Erase the file
+                    method.Erase(stream, long.MaxValue, ManagerLibrary.Instance.PrngRegistrar[
+                            ManagerLibrary.Settings.ActivePrng], null);
+                }
+                finally
+                {
+                    //Make sure the file length is restored!
+                    stream.SetLength(fileLength);
+
+                    //Then destroy the stream
+                    stream.Close();
+                }
+            }
+            catch (ArgumentException e)
+            {
+                //This is an undocumented exception: when the path we are setting
+                //cannot be accessed (ERROR_ACCESS_DENIED is returned) an
+                //ArgumentException is raised (no idea why!)
+                throw new UnauthorizedAccessException(e.Message, e);
             }
             finally
             {
+                //Reset the file attributes
+                streamInfo.Attributes = attributes;
+
                 //Reset the file times
                 streamInfo.SetTimes(MinTimestamp, created, lastWrite, lastAccess);
@@ -375 +377 @@
         }
 
-        public override long GetFileArea(string filePath)
-        {
-            StreamInfo info = new StreamInfo(filePath);
+        public override long GetFileArea(StreamInfo info)
+        {
             VolumeInfo volume = VolumeInfo.FromMountPoint(info.Directory.FullName);
             long clusterSize = volume.ClusterSize;