First implementation of CachingFileStorage

+ some tests to test loading and saving to cached storage

src/Kp2aBusinessLogic/Io/BuiltInFileStorage.cs

@@ -36,7 +36,7 @@ namespace keepass2android.Io
 			TimeSpan diff = currentModificationDate - previousDate;
 			return diff > TimeSpan.FromSeconds(1);
 			//don't use > operator because milliseconds are truncated
-			return File.GetLastWriteTimeUtc(ioc.Path) - previousDate >= TimeSpan.FromSeconds(1);
+			//return File.GetLastWriteTimeUtc(ioc.Path) - previousDate >= TimeSpan.FromSeconds(1);
 		}
 
 		

src/Kp2aBusinessLogic/Io/CachingFileStorage.cs

@@ -0,0 +1,325 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Net;
+using System.Security.Cryptography;
+using System.Text;
+using KeePassLib.Cryptography;
+using KeePassLib.Serialization;
+using KeePassLib.Utility;
+
+namespace keepass2android.Io
+{
+	/// <summary>
+	/// Interface for classes which can handle certain Cache events on a higher level (e.g. by user interaction)
+	/// </summary>
+	public interface ICacheSupervisor
+	{
+		/// <summary>
+		/// called when a save operation only updated the cache but not the remote file
+		/// </summary>
+		/// <param name="ioc">The file which we tried to write</param>
+		/// <param name="e">The exception why the remote file couldn't be updated</param>
+		void CouldntSaveToRemote(IOConnectionInfo ioc, Exception e);
+
+		/// <summary>
+		/// Called when only the local file could be opened during an open operation.
+		/// </summary>
+		void CouldntOpenFromRemote(IOConnectionInfo ioc, Exception ex);
+
+		/// <summary>
+		/// Called to notify the supervisor that the file described by ioc is opened from the cache because there's a conflict
+		/// with local and remote changes
+		/// </summary>
+		/// <param name="ioc"></param>
+		void NotifyOpenFromLocalDueToConflict(IOConnectionInfo ioc);
+	}
+
+	/// <summary>
+	/// Implements the IFileStorage interface as a proxy: A base storage is used as a remote storage. Local files are used to cache the
+	/// files on remote.
+	/// </summary>
+	public class CachingFileStorage: IFileStorage
+	{
+		private readonly IFileStorage _cachedStorage;
+		private readonly ICacheSupervisor _cacheSupervisor;
+		private readonly string _streamCacheDir;
+
+		public CachingFileStorage(IFileStorage cachedStorage, string cacheDir, ICacheSupervisor cacheSupervisor)
+		{
+			_cachedStorage = cachedStorage;
+			_cacheSupervisor = cacheSupervisor;
+			_streamCacheDir = cacheDir + Java.IO.File.Separator + "OfflineCache" + Java.IO.File.Separator;
+			if (!Directory.Exists(_streamCacheDir))
+				Directory.CreateDirectory(_streamCacheDir);
+			
+		}
+
+		public void ClearCache()
+		{
+			IoUtil.DeleteDir(new Java.IO.File(_streamCacheDir), true);
+		}
+
+		public void DeleteFile(IOConnectionInfo ioc)
+		{
+			if (IsCached(ioc))
+			{
+				File.Delete(CachedFilePath(ioc));
+				File.Delete(VersionFilePath(ioc));
+				File.Delete(BaseVersionFilePath(ioc));
+			}
+			
+			_cachedStorage.DeleteFile(ioc);
+		}
+
+		private string CachedFilePath(IOConnectionInfo ioc)
+		{
+			SHA256Managed sha256 = new SHA256Managed();
+			string iocAsHexString = MemUtil.ByteArrayToHexString(sha256.ComputeHash(Encoding.Unicode.GetBytes(ioc.Path.ToCharArray())))+".cache";
+			return _streamCacheDir + iocAsHexString;
+		}
+
+		private bool IsCached(IOConnectionInfo ioc)
+		{
+			return File.Exists(CachedFilePath(ioc))
+				&& File.Exists(VersionFilePath(ioc))
+				&& File.Exists(BaseVersionFilePath(ioc));
+		}
+
+		public bool CheckForFileChangeFast(IOConnectionInfo ioc, string previousFileVersion)
+		{
+			//see comment in GetCurrentFileVersionFast
+			return false;
+		}
+
+		public string GetCurrentFileVersionFast(IOConnectionInfo ioc)
+		{
+			//fast file version checking is not supported by CachingFileStorage:
+			//it's hard to return good versions in cases that the base source is offline
+			//or after modifying the cache.
+			//It's probably not relevant because fast file version checking is meant for local storage
+			//which is not cached.
+			return String.Empty;
+		}
+
+		private string VersionFilePath(IOConnectionInfo ioc)
+		{
+			return CachedFilePath(ioc)+".version";
+		}
+
+		private string BaseVersionFilePath(IOConnectionInfo ioc)
+		{
+			return CachedFilePath(ioc) + ".baseversion";
+		}
+
+		public Stream OpenFileForRead(IOConnectionInfo ioc)
+		{
+			string cachedFilePath = CachedFilePath(ioc);
+			try
+			{
+				if (!IsCached(ioc)
+				    || File.ReadAllText(VersionFilePath(ioc)) == File.ReadAllText(BaseVersionFilePath(ioc)))
+				{
+					return OpenFileForReadWhenNoLocalChanges(ioc, cachedFilePath);
+				}
+				else
+				{
+					return OpenFileForReadWhenLocalChanges(ioc, cachedFilePath);
+				}
+			}
+			catch (Exception ex)
+			{
+				Kp2aLog.Log("couldn't open from remote " + ioc.Path);
+				Kp2aLog.Log(ex.ToString());
+
+				_cacheSupervisor.CouldntOpenFromRemote(ioc, ex);
+				return File.OpenRead(cachedFilePath);
+			}
+		}
+
+		private Stream OpenFileForReadWhenLocalChanges(IOConnectionInfo ioc, string cachedFilePath)
+		{
+			//file is cached but has local modifications
+			//try to upload the changes if remote file doesn't have changes as well:
+			var hash = Calculate(ioc);
+
+			if (File.ReadAllText(BaseVersionFilePath(ioc)) == hash)
+			{
+				//no changes in remote file -> upload
+				using (Stream localData = File.OpenRead(CachedFilePath(ioc)))
+				{
+					TryUpdateRemoteFile(localData, ioc, true, hash);
+				}
+			}
+			else
+			{
+				//conflict: both files changed.
+				//signal that we're loading from local
+				_cacheSupervisor.NotifyOpenFromLocalDueToConflict(ioc);
+			}
+			return File.OpenRead(cachedFilePath);
+		}
+
+		private string Calculate(IOConnectionInfo ioc)
+		{
+			MemoryStream remoteData = new MemoryStream();
+			string hash;
+			using (
+				HashingStreamEx hashingRemoteStream = new HashingStreamEx(_cachedStorage.OpenFileForRead(ioc), false,
+				                                                          new SHA256Managed()))
+			{
+				hashingRemoteStream.CopyTo(remoteData);
+				hashingRemoteStream.Close();
+				hash = MemUtil.ByteArrayToHexString(hashingRemoteStream.Hash);
+			}
+			return hash;
+		}
+
+		private Stream OpenFileForReadWhenNoLocalChanges(IOConnectionInfo ioc, string cachedFilePath)
+		{
+			//open stream:
+			using (Stream file = _cachedStorage.OpenFileForRead(ioc))
+			{
+				//copy to cache: 
+				//note: we might use the file version to check if it's already in the cache and if copying is required. 
+				//However, this is safer.
+				string fileHash;
+				using (HashingStreamEx cachedFile = new HashingStreamEx(File.Create(cachedFilePath), true, new SHA256Managed()))
+				{
+					file.CopyTo(cachedFile);
+					cachedFile.Close();
+					fileHash = MemUtil.ByteArrayToHexString(cachedFile.Hash);
+				}
+				//save hash in cache files:
+				File.WriteAllText(VersionFilePath(ioc), fileHash);
+				File.WriteAllText(BaseVersionFilePath(ioc), fileHash);
+
+				return File.OpenRead(cachedFilePath);	
+			}
+			
+		}
+
+		private void TryUpdateRemoteFile(Stream cachedData, IOConnectionInfo ioc, bool useFileTransaction, string hash)
+		{
+			try
+			{
+				//try to write to remote:
+				using (
+					IWriteTransaction remoteTrans = _cachedStorage.OpenWriteTransaction(ioc, useFileTransaction))
+				{
+					Stream remoteStream = remoteTrans.OpenFile();
+					cachedData.CopyTo(remoteStream);
+					remoteStream.Close();
+					remoteTrans.CommitWrite();
+				}
+				//success. Update base-version of cache:
+				File.WriteAllText(VersionFilePath(ioc), hash);
+			}
+			catch (Exception e)
+			{
+				Kp2aLog.Log("couldn't save to remote " + ioc.Path);
+				Kp2aLog.Log(e.ToString());
+				//notify the supervisor so it might display a warning or schedule a retry
+				_cacheSupervisor.CouldntSaveToRemote(ioc, e);
+			}
+		}
+
+		private class CachedWriteTransaction: IWriteTransaction
+		{
+			private class CachedWriteMemoryStream : MemoryStream
+			{
+				private readonly IOConnectionInfo ioc;
+				private readonly CachingFileStorage _cachingFileStorage;
+				private readonly bool _useFileTransaction;
+
+				public CachedWriteMemoryStream(IOConnectionInfo ioc, CachingFileStorage cachingFileStorage, bool useFileTransaction)
+				{
+					this.ioc = ioc;
+					_cachingFileStorage = cachingFileStorage;
+					_useFileTransaction = useFileTransaction;
+				}
+
+
+				public override void Close()
+				{
+					//write file to cache:
+					//(note: this might overwrite local changes. It's assumed that a sync operation or check was performed before
+					string hash;
+					using (var hashingStream = new HashingStreamEx(File.Create(_cachingFileStorage.CachedFilePath(ioc)), true, new SHA256Managed()))
+					{
+						Position = 0;
+						CopyTo(hashingStream);
+
+						hashingStream.Close();
+						hash = MemUtil.ByteArrayToHexString(hashingStream.Hash);
+					}
+
+					File.WriteAllText(_cachingFileStorage.VersionFilePath(ioc), hash);
+					//update file on remote. This might overwrite changes there as well, see above.
+					Position = 0;
+					_cachingFileStorage.TryUpdateRemoteFile(this, ioc, _useFileTransaction, hash);
+				
+					base.Close();
+				}
+
+			}
+
+			private readonly IOConnectionInfo _ioc;
+			private readonly bool _useFileTransaction;
+			private readonly CachingFileStorage _cachingFileStorage;
+			private MemoryStream _memoryStream;
+			private bool _committed;
+
+			public CachedWriteTransaction(IOConnectionInfo ioc, bool useFileTransaction, CachingFileStorage cachingFileStorage)
+			{
+				_ioc = ioc;
+				_useFileTransaction = useFileTransaction;
+				_cachingFileStorage = cachingFileStorage;
+			}
+
+			public void Dispose()
+			{
+				if (!_committed)
+					_memoryStream.Dispose();
+			}
+
+			public Stream OpenFile()
+			{
+				_memoryStream = new CachedWriteMemoryStream(_ioc, _cachingFileStorage, _useFileTransaction);
+				return _memoryStream;
+			}
+
+			public void CommitWrite()
+			{	
+				//the transaction is committed in the stream's Close
+				_committed = true;
+			}
+
+		}
+
+
+		public IWriteTransaction OpenWriteTransaction(IOConnectionInfo ioc, bool useFileTransaction)
+		{
+			//create a transaction which writes to memory stream
+			//on close: write to cache. If possible, write to online 
+			//update versions
+			return new CachedWriteTransaction(ioc, useFileTransaction, this);
+		}
+
+		public bool CompleteIoId()
+		{
+			throw new NotImplementedException();
+		}
+
+		public bool? FileExists()
+		{
+			throw new NotImplementedException();
+		}
+
+		public string GetFilenameWithoutPathAndExt(IOConnectionInfo ioc)
+		{
+			return UrlUtil.StripExtension(
+				UrlUtil.GetFileName(ioc.Path));
+		}
+	}
+}

src/Kp2aBusinessLogic/Io/IoUtil.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Java.IO;
+
+namespace keepass2android.Io
+{
+	public static class IoUtil
+	{
+		public static bool DeleteDir(File dir, bool contentsOnly=false)
+		{
+			if (dir != null && dir.IsDirectory)
+			{
+				String[] children = dir.List();
+				for (int i = 0; i < children.Length; i++)
+				{
+					bool success = DeleteDir(new File(dir, children[i]));
+					if (!success)
+					{
+						return false;
+					}
+				}
+			}
+			
+			if (contentsOnly)
+				return true;
+
+			// The directory is now empty so delete it
+			return dir.Delete();
+		}
+
+
+	}
+}

src/Kp2aBusinessLogic/Kp2aBusinessLogic.csproj

@@ -52,7 +52,9 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="Io\BuiltInFileStorage.cs" />
+    <Compile Include="Io\CachingFileStorage.cs" />
     <Compile Include="Io\IFileStorage.cs" />
+    <Compile Include="Io\IoUtil.cs" />
     <Compile Include="IProgressDialog.cs" />
     <Compile Include="PreferenceKey.cs" />
     <Compile Include="UiStringKey.cs" />

src/Kp2aBusinessLogic/database/Database.cs

@@ -124,7 +124,9 @@ namespace keepass2android
 			try
 			{
 				IFileStorage fileStorage = _app.GetFileStorage(iocInfo);
+				var fileVersion = _app.GetFileStorage(iocInfo).GetCurrentFileVersionFast(iocInfo);
 				pwDatabase.Open(fileStorage.OpenFileForRead(iocInfo), fileStorage.GetFilenameWithoutPathAndExt(iocInfo), iocInfo, compositeKey, status);
+				LastFileVersion = fileVersion;
 			}
 			catch (Exception)
 			{
@@ -140,8 +142,6 @@ namespace keepass2android
 			
 			status.UpdateSubMessage("");
 
-			LastFileVersion = _app.GetFileStorage(iocInfo).GetCurrentFileVersionFast(iocInfo);
-
 			Root = pwDatabase.RootGroup;
 			PopulateGlobals(Root);
 

src/Kp2aUnitTests/Kp2aUnitTests.csproj

@@ -66,6 +66,7 @@
     <Compile Include="TestKp2aApp.cs" />
     <Compile Include="TestLoadDb.cs" />
     <Compile Include="TestLoadDbCredentials.cs" />
+    <Compile Include="TestCachingFileStorage.cs" />
     <Compile Include="TestSaveDb.cs" />
   </ItemGroup>
   <ItemGroup>

src/Kp2aUnitTests/MainActivity.cs

@@ -19,8 +19,9 @@ namespace Kp2aUnitTests
             TestRunner runner = new TestRunner();
             // Run all tests from this assembly
             //runner.AddTests(Assembly.GetExecutingAssembly());
-			//runner.AddTests(new List<Type> { typeof(TestSaveDb)});
+			runner.AddTests(new List<Type> { typeof(TestCachingFileStorage) });
-			runner.AddTests(typeof(TestSaveDb).GetMethod("TestLoadEditSaveWithSyncKdbp"));
+			//runner.AddTests(typeof(TestCachingFileStorage).GetMethod("TestSaveToRemote"));
+			//runner.AddTests(typeof(TestLoadDb).GetMethod("TestLoadKdbpWithPasswordOnly"));
 			//runner.AddTests(typeof(TestSaveDb).GetMethod("TestLoadKdbxAndSaveKdbp_TestIdenticalFiles"));
             return runner;
         }

src/Kp2aUnitTests/TestCachingFileStorage.cs

@@ -0,0 +1,358 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using Android.App;
+using KeePassLib.Serialization;
+using KeePassLib.Utility;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using keepass2android.Io;
+
+namespace Kp2aUnitTests
+{
+	[TestClass]
+	class TestCachingFileStorage: TestBase
+	{
+		private TestFileStorage _testFileStorage;
+		private CachingFileStorage _fileStorage;
+		private static readonly string CachingTestFile = DefaultDirectory + "cachingTestFile.txt";
+		private string _defaultCacheFileContents = "default contents";
+		private TestCacheSupervisor _testCacheSupervisor;
+
+		class TestCacheSupervisor: ICacheSupervisor
+		{
+			public bool CouldntOpenFromRemoteCalled { get; set; }
+			public bool CouldntSaveToRemoteCalled { get; set; }
+			public bool NotifyOpenFromLocalDueToConflictCalled { get; set; }
+
+
+			public void CouldntSaveToRemote(IOConnectionInfo ioc, Exception e)
+			{
+				CouldntSaveToRemoteCalled = true;
+			}
+
+			public void CouldntOpenFromRemote(IOConnectionInfo ioc, Exception ex)
+			{
+				CouldntOpenFromRemoteCalled = true;
+			}
+
+			public void NotifyOpenFromLocalDueToConflict(IOConnectionInfo ioc)
+			{
+				NotifyOpenFromLocalDueToConflictCalled = true;
+			}
+		}
+
+		public class TestFileStorage: IFileStorage
+		{
+			private BuiltInFileStorage _builtIn = new BuiltInFileStorage();
+
+			public bool Offline { get; set; }
+
+
+			public void DeleteFile(IOConnectionInfo ioc)
+			{
+				if (Offline)
+					throw new IOException("offline");
+				_builtIn.DeleteFile(ioc);
+			}
+
+			public bool CheckForFileChangeFast(IOConnectionInfo ioc, string previousFileVersion)
+			{
+				if (Offline)
+					return false;
+				return _builtIn.CheckForFileChangeFast(ioc, previousFileVersion);
+			}
+
+			public string GetCurrentFileVersionFast(IOConnectionInfo ioc)
+			{
+				if (Offline)
+					throw new IOException("offline");
+				return _builtIn.GetCurrentFileVersionFast(ioc);
+			}
+
+			public Stream OpenFileForRead(IOConnectionInfo ioc)
+			{
+				if (Offline)
+					throw new IOException("offline");
+				return _builtIn.OpenFileForRead(ioc);
+			}
+
+			public IWriteTransaction OpenWriteTransaction(IOConnectionInfo ioc, bool useFileTransaction)
+			{
+				if (Offline)
+					throw new IOException("offline");
+				return new TestFileTransaction(ioc, useFileTransaction, Offline);
+			}
+
+			public class TestFileTransaction : IWriteTransaction
+			{
+				private readonly bool _offline;
+				private readonly FileTransactionEx _transaction;
+
+				public TestFileTransaction(IOConnectionInfo ioc, bool useFileTransaction, bool offline)
+				{
+					_offline = offline;
+					_transaction = new FileTransactionEx(ioc, useFileTransaction);
+				}
+
+				public void Dispose()
+				{
+
+				}
+
+				public Stream OpenFile()
+				{
+					if (_offline)
+						throw new IOException("offline");
+					return _transaction.OpenWrite();
+				}
+
+				public void CommitWrite()
+				{
+					if (_offline)
+						throw new IOException("offline");
+					_transaction.CommitWrite();
+				}
+			}
+
+			public bool CompleteIoId()
+			{
+				throw new NotImplementedException();
+			}
+
+			public bool? FileExists()
+			{
+				throw new NotImplementedException();
+			}
+
+			public string GetFilenameWithoutPathAndExt(IOConnectionInfo ioc)
+			{
+				return _builtIn.GetFilenameWithoutPathAndExt(ioc);
+			}
+		}
+
+		/// <summary>
+		/// Tests correct behavior in case that either remote or cache are not available
+		/// </summary>
+		[TestMethod]
+		public void TestMakeAccessibleWhenOffline()
+		{
+			SetupFileStorage();
+			
+			//read the file once. Should now be in the cache.
+			MemoryStream fileContents = ReadToMemoryStream(_fileStorage, CachingTestFile);
+
+			//check it's the correct data:
+			Assert.AreEqual(MemoryStreamToString(fileContents), _defaultCacheFileContents);
+
+			//let the base file storage go offline:
+			_testFileStorage.Offline = true;
+
+			//now try to read the file again:
+			MemoryStream fileContents2 = ReadToMemoryStream(_fileStorage, CachingTestFile);
+
+			AssertEqual(fileContents, fileContents2);
+
+			Assert.IsTrue(_testCacheSupervisor.CouldntOpenFromRemoteCalled);
+			Assert.IsFalse(_testCacheSupervisor.CouldntSaveToRemoteCalled);
+			
+
+		}
+
+		private string MemoryStreamToString(MemoryStream stream)
+		{
+			stream.Position = 0;
+			StreamReader r = new StreamReader(stream);
+			return r.ReadToEnd();
+		}
+
+		/// <summary>
+		/// tests correct behaviour after modifiying the local cache (with the remote file being unchanged) and remote being 
+		/// either unavailable or available
+		/// </summary>
+		[TestMethod]
+		public void TestSyncOnLoadWhenLocalFileChanged()
+		{
+			SetupFileStorage();
+
+			
+			//read the file once. Should now be in the cache.
+			ReadToMemoryStream(_fileStorage, CachingTestFile);
+
+			Assert.IsFalse(_testCacheSupervisor.CouldntOpenFromRemoteCalled);
+			Assert.IsFalse(_testCacheSupervisor.CouldntSaveToRemoteCalled);
+
+			//let the base file storage go offline:
+			_testFileStorage.Offline = true;
+
+			//write something to the cache:
+			string newContent = "new content";
+			WriteContentToCacheFile(newContent);
+
+			Assert.IsFalse(_testCacheSupervisor.CouldntOpenFromRemoteCalled);
+			Assert.IsTrue(_testCacheSupervisor.CouldntSaveToRemoteCalled);
+			_testCacheSupervisor.CouldntSaveToRemoteCalled = false;
+
+			//now try to read the file again:
+			MemoryStream fileContents2 = ReadToMemoryStream(_fileStorage, CachingTestFile);
+
+			Assert.IsTrue(_testCacheSupervisor.CouldntOpenFromRemoteCalled);
+			Assert.IsFalse(_testCacheSupervisor.CouldntSaveToRemoteCalled);
+			_testCacheSupervisor.CouldntOpenFromRemoteCalled = false;
+
+			//should return the written content:
+			Assert.AreEqual(MemoryStreamToString(fileContents2), newContent);
+
+			//now go online and read again. This should trigger a sync and the modified data must be returned
+			_testFileStorage.Offline = false;
+			MemoryStream fileContents3 = ReadToMemoryStream(_fileStorage, CachingTestFile);
+			Assert.AreEqual(MemoryStreamToString(fileContents3), newContent);
+
+			Assert.IsFalse(_testCacheSupervisor.CouldntOpenFromRemoteCalled);
+			Assert.IsFalse(_testCacheSupervisor.CouldntSaveToRemoteCalled);
+
+			//ensure the data on the remote was synced:
+			MemoryStream fileContents4 = ReadToMemoryStream(_testFileStorage, CachingTestFile);
+			Assert.AreEqual(MemoryStreamToString(fileContents4), newContent);
+		}
+
+		/// <summary>
+		/// tests correct behaviour after modifiying both the local cache and the remote file
+		/// </summary>
+		[TestMethod]
+		public void TestLoadLocalWhenBothFilesChanged()
+		{
+			SetupFileStorage();
+
+			//read the file once. Should now be in the cache.
+			ReadToMemoryStream(_fileStorage, CachingTestFile);
+
+			Assert.IsFalse(_testCacheSupervisor.CouldntOpenFromRemoteCalled);
+			Assert.IsFalse(_testCacheSupervisor.CouldntSaveToRemoteCalled);
+
+			//let the base file storage go offline:
+			_testFileStorage.Offline = true;
+
+			//write something to the cache:
+			string newLocalContent = "new local content";
+			WriteContentToCacheFile(newLocalContent);
+
+			Assert.IsFalse(_testCacheSupervisor.CouldntOpenFromRemoteCalled);
+			Assert.IsTrue(_testCacheSupervisor.CouldntSaveToRemoteCalled);
+			_testCacheSupervisor.CouldntSaveToRemoteCalled = false;
+
+			//write something to the remote file:
+			File.WriteAllText(CachingTestFile, "new remote content");
+
+			//go online again:
+			_testFileStorage.Offline = false;
+
+			//now try to read the file again:
+			MemoryStream fileContents2 = ReadToMemoryStream(_fileStorage, CachingTestFile);
+
+			//should return the local content:
+			Assert.AreEqual(MemoryStreamToString(fileContents2), newLocalContent);
+
+			//but a notification about the conflict should be made:
+			Assert.IsFalse(_testCacheSupervisor.CouldntOpenFromRemoteCalled);
+			Assert.IsFalse(_testCacheSupervisor.CouldntSaveToRemoteCalled);
+			Assert.IsTrue(_testCacheSupervisor.NotifyOpenFromLocalDueToConflictCalled);
+			_testCacheSupervisor.NotifyOpenFromLocalDueToConflictCalled = false;
+
+			
+
+		}
+
+
+	
+		[TestMethod]
+		public void TestSaveToRemote()
+		{
+			SetupFileStorage();
+
+			//read the file once. Should now be in the cache.
+			ReadToMemoryStream(_fileStorage, CachingTestFile);
+
+			//write something to the cache:
+			string newContent = "new content";
+			WriteContentToCacheFile(newContent);
+
+			Assert.IsFalse(_testCacheSupervisor.CouldntOpenFromRemoteCalled);
+			Assert.IsFalse(_testCacheSupervisor.CouldntSaveToRemoteCalled);
+
+			Assert.AreEqual(newContent, File.ReadAllText(CachingTestFile));
+		}
+
+		private void WriteContentToCacheFile(string newContent)
+		{
+		
+			using (var trans = _fileStorage.OpenWriteTransaction(IocForCacheFile, true))
+			{
+				StreamWriter sw = new StreamWriter(trans.OpenFile());
+				sw.Write(newContent);
+				sw.Flush();
+				sw.Close();
+				trans.CommitWrite();
+			}
+		}
+
+		protected IOConnectionInfo IocForCacheFile
+		{
+			get { return new IOConnectionInfo() { Path = CachingTestFile }; }
+		}
+
+		private void SetupFileStorage()
+		{
+			_testFileStorage = new TestFileStorage();
+			_testCacheSupervisor = new TestCacheSupervisor();
+			_fileStorage = new CachingFileStorage(_testFileStorage, Application.Context.CacheDir.Path, _testCacheSupervisor);
+			_fileStorage.ClearCache();
+			File.WriteAllText(CachingTestFile, _defaultCacheFileContents);
+		}
+
+		private static MemoryStream ReadToMemoryStream(IFileStorage fileStorage, string filename)
+		{
+			Stream fileStream = fileStorage.OpenFileForRead(new IOConnectionInfo() {Path = filename});
+			MemoryStream fileContents = new MemoryStream();
+			fileStream.CopyTo(fileContents);
+			fileStream.Close();
+			return fileContents;
+		}
+
+
+		static bool StreamEquals(Stream stream1, Stream stream2)
+		{
+			const int bufferSize = 2048;
+			byte[] buffer1 = new byte[bufferSize]; //buffer size
+			byte[] buffer2 = new byte[bufferSize];
+			while (true)
+			{
+				int count1 = stream1.Read(buffer1, 0, bufferSize);
+				int count2 = stream2.Read(buffer2, 0, bufferSize);
+
+				if (count1 != count2)
+					return false;
+
+				if (count1 == 0)
+					return true;
+
+				// You might replace the following with an efficient "memcmp"
+				if (!buffer1.Take(count1).SequenceEqual(buffer2.Take(count2)))
+					return false;
+			}
+		}
+
+		private void AssertEqual(MemoryStream s1, MemoryStream s2)
+		{
+			s1.Seek(0,0);
+			s2.Seek(0, 0);
+			Assert.AreEqual(s1.Length, s2.Length);
+			Assert.AreEqual(0, s1.Position);
+			Assert.AreEqual(0, s2.Position);
+			Assert.IsTrue(StreamEquals(s1, s2));
+		}
+
+		//todo test delete
+	}
+}

src/Kp2aUnitTests/TestSaveDb.cs

@@ -232,26 +232,18 @@ namespace Kp2aUnitTests
 		}
 
 
-
+		/*
 		[TestMethod]
 		public void TestSaveAsWhenReadOnly()
 		{
 			Assert.Fail("TODO: Test ");
 		}
 
-
-		[TestMethod]
-		public void TestReloadWhenCancelSync()
-		{
-			//when a change is detected and the user cancels saving, the app should display the "file was modified - reload?" question.
-			Assert.Fail("TODO: Test ");
-		}
-
 		[TestMethod]
 		public void TestSaveAsWhenSyncError()
 		{
 			Assert.Fail("TODO: Test ");
-		}
+		}*/
 
 		[TestMethod]
 		public void TestLoadAndSave_TestIdenticalFiles()

src/keepass2android/AttachmentContentProvider.cs

@@ -11,7 +11,8 @@ namespace keepass2android
 	/// </summary>
 	[ContentProvider(new[]{"keepass2android."+AppNames.PackagePart+".provider"})] 
 	public class AttachmentContentProvider : ContentProvider {
-		
+		public const string AttachmentCacheSubDir = "AttachmentCache";
+
 		private const String ClassName = "AttachmentContentProvider";
 		
 		// The authority is the symbolic name for the provider class
@@ -37,7 +38,8 @@ namespace keepass2android
 				// E.g.
 				// 'content://keepass2android.provider/Test.txt'
 				// Take this and build the path to the file
-				String fileLocation = Context.CacheDir + File.Separator
+				
+				String fileLocation = Context.CacheDir + File.Separator + AttachmentCacheSubDir + File.Separator
 					+ uri.LastPathSegment;
 					
 				// Create & return a ParcelFileDescriptor pointing to the file

src/keepass2android/EntryActivity.cs

@@ -35,6 +35,7 @@ using KeePassLib.Security;
 using Android.Webkit;
 using Android.Graphics;
 using Java.IO;
+using keepass2android.Io;
 
 namespace keepass2android
 {
@@ -230,7 +231,7 @@ namespace keepass2android
 			ISharedPreferences prefs = PreferenceManager.GetDefaultSharedPreferences(this);
 			string binaryDirectory = prefs.GetString(GetString(Resource.String.BinaryDirectory_key), GetString(Resource.String.BinaryDirectory_default));
 			if (writeToCacheDirectory)
-				binaryDirectory = CacheDir.Path;
+				binaryDirectory = CacheDir.Path + File.Separator + AttachmentContentProvider.AttachmentCacheSubDir;
 		
 			string filepart = key;
 			if (writeToCacheDirectory)
@@ -528,30 +529,16 @@ namespace keepass2android
 		
 		public void ClearCache() {
 			try {
-				File dir = CacheDir;
+				File dir = new File(CacheDir.Path + File.Separator + AttachmentContentProvider.AttachmentCacheSubDir);
-				if (dir != null && dir.IsDirectory) {
+				if (dir.IsDirectory) {
-					DeleteDir(dir);
+					IoUtil.DeleteDir(dir);
 				}
 			} catch (Exception) {
 
 			}
 		}
 		
-		public static bool DeleteDir(File dir) {
+		
-			if (dir != null && dir.IsDirectory) {
-				String[] children = dir.List();
-				for (int i = 0; i < children.Length; i++) {
-					bool success = DeleteDir(new File(dir, children[i]));
-					if (!success) {
-						return false;
-					}
-				}
-			}
-			
-			// The directory is now empty so delete it
-			return dir.Delete();
-		}
-
 		public override bool OnOptionsItemSelected(IMenuItem item) {
 			switch ( item.ItemId ) {
 			case Resource.Id.menu_donate:

src/keepass2android/keepass2android.csproj

@@ -150,7 +150,9 @@
     <None Include="Resources\drawable\Thumbs.db">
       <Visible>False</Visible>
     </None>
-    <None Include="Properties\AndroidManifest.xml" />
+    <None Include="Properties\AndroidManifest.xml">
+      <SubType>Designer</SubType>
+    </None>
     <None Include="filelist.txt">
       <Visible>False</Visible>
     </None>