Implement file polling for disk session cache

For use in case FileSystemWatcher does not work, see #684

MinecraftClient/MinecraftClient.csproj

@@ -97,6 +97,7 @@
     <Compile Include="Commands\Script.cs" />
     <Compile Include="Commands\Send.cs" />
     <Compile Include="Commands\Set.cs" />
+    <Compile Include="Protocol\Session\SessionFileMonitor.cs" />
     <Compile Include="WinAPI\ConsoleIcon.cs" />
     <Compile Include="ConsoleIO.cs" />
     <Compile Include="Crypto\Streams\BouncyAes\AesFastEngine.cs" />

MinecraftClient/Protocol/Session/SessionCache.cs

@@ -23,8 +23,8 @@ namespace MinecraftClient.Protocol.Session
             "launcher_profiles.json"
         );
 
+        private static SessionFileMonitor cachemonitor;
         private static Dictionary<string, SessionToken> sessions = new Dictionary<string, SessionToken>();
-        private static FileSystemWatcher cachemonitor = new FileSystemWatcher();
         private static Timer updatetimer = new Timer(100);
         private static List<KeyValuePair<string, SessionToken>> pendingadds = new List<KeyValuePair<string, SessionToken>>();
         private static BinaryFormatter formatter = new BinaryFormatter();
@@ -81,15 +81,8 @@ namespace MinecraftClient.Protocol.Session
         /// <returns>TRUE if session tokens are seeded from file</returns>
         public static bool InitializeDiskCache()
         {
-            cachemonitor.Path = AppDomain.CurrentDomain.BaseDirectory;
+            cachemonitor = new SessionFileMonitor(AppDomain.CurrentDomain.BaseDirectory, SessionCacheFilePlaintext, new FileSystemEventHandler(OnChanged));
-            cachemonitor.IncludeSubdirectories = false;
-            cachemonitor.Filter = SessionCacheFilePlaintext;
-            cachemonitor.NotifyFilter = NotifyFilters.LastWrite;
-            cachemonitor.Changed += new FileSystemEventHandler(OnChanged);
-            cachemonitor.EnableRaisingEvents = true;
-
             updatetimer.Elapsed += HandlePending;
-
             return LoadFromDisk();
         }
 

MinecraftClient/Protocol/Session/SessionFileMonitor.cs

@@ -0,0 +1,83 @@
+using System;
+using System.IO;
+using System.Threading;
+
+namespace MinecraftClient.Protocol.Session
+{
+    /// <summary>
+    /// Monitor session file changes on disk
+    /// </summary>
+    class SessionFileMonitor
+    {
+        private FileSystemWatcher monitor;
+        private Thread polling;
+
+        /// <summary>
+        /// Create a new SessionFileMonitor and start monitoring
+        /// </summary>
+        /// <param name="folder">Folder to monitor</param>
+        /// <param name="filename">Filename inside folder</param>
+        /// <param name="handler">Callback for file changes</param>
+        public SessionFileMonitor(string folder, string filename, FileSystemEventHandler handler)
+        {
+            if (Settings.DebugMessages)
+                ConsoleIO.WriteLineFormatted("§8Initializing disk session cache using FileSystemWatcher");
+
+            try
+            {
+                monitor = new FileSystemWatcher();
+                monitor.Path = folder;
+                monitor.IncludeSubdirectories = false;
+                monitor.Filter = filename;
+                monitor.NotifyFilter = NotifyFilters.LastWrite;
+                monitor.Changed += handler;
+                monitor.EnableRaisingEvents = true;
+            }
+            catch
+            {
+                if (Settings.DebugMessages)
+                    ConsoleIO.WriteLineFormatted("§8Failed to initialize FileSystemWatcher, retrying using Polling");
+
+                polling = new Thread(() => PollingThread(folder, filename, handler));
+                polling.Start();
+            }
+        }
+
+        /// <summary>
+        /// Fallback polling thread for use when operating system does not support FileSystemWatcher
+        /// </summary>
+        /// <param name="folder">Folder to monitor</param>
+        /// <param name="filename">File name to monitor</param>
+        /// <param name="handler">Callback when file changes</param>
+        private void PollingThread(string folder, string filename, FileSystemEventHandler handler)
+        {
+            string filePath = String.Concat(folder, Path.DirectorySeparatorChar, filename);
+            DateTime lastWrite = GetLastWrite(filePath);
+            while (true)
+            {
+                Thread.Sleep(5000);
+                DateTime lastWriteNew = GetLastWrite(filePath);
+                if (lastWriteNew != lastWrite)
+                {
+                    lastWrite = lastWriteNew;
+                    handler(this, new FileSystemEventArgs(WatcherChangeTypes.Changed, folder, filename));
+                }
+            }
+        }
+
+        /// <summary>
+        /// Get last write for a given file
+        /// </summary>
+        /// <param name="path">File path to get last write from</param>
+        /// <returns>Last write time, or DateTime.MinValue if the file does not exist</returns>
+        private DateTime GetLastWrite(string path)
+        {
+            FileInfo fileInfo = new FileInfo(path);
+            if (fileInfo.Exists)
+            {
+                return fileInfo.LastWriteTime;
+            }
+            else return DateTime.MinValue;
+        }
+    }
+}