Changed IPC communication to use memory mapped memory instead of physical file to store the name of the DS4Form window class.

DS4Windows/DS4Forms/DS4Form.cs

@@ -87,9 +87,6 @@ namespace DS4Windows.Forms
         [DllImport("psapi.dll")]
         private static extern uint GetModuleFileNameEx(IntPtr hWnd, IntPtr hModule, StringBuilder lpFileName, int nSize);
 
-        [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
-        private static extern int GetClassName(IntPtr hWnd, StringBuilder lpClassName, int nMaxCount);
-
         public DS4Form(string[] args)
         {
             Global.FindConfigLocation();
@@ -391,16 +388,7 @@ namespace DS4Windows.Forms
             if (!(StartMinimized || mini))
                 Form_Resize(null, null);
 
-            // Write current window class name as InterProcessCommunication identifier. The IPC classname is used in WM_DATACOPY messaging interface. .NET WinForms creates a semi-random clas names per application.
+            Program.CreateIPCClassNameMMF(this.Handle);
-            StringBuilder wndClassNameStr = new StringBuilder(256);
-            if (GetClassName(this.Handle, wndClassNameStr, wndClassNameStr.Capacity) != 0 && wndClassNameStr.Length > 0)
-            {
-                if (System.IO.File.Exists(appdatapath + "\\IPCClassName.dat") && System.IO.File.ReadAllText(appdatapath + "\\IPCClassName.dat") == wndClassNameStr.ToString())
-                    wndClassNameStr.Clear(); // The wnd classname is still the same, so no need to re-write it
-            
-                if(wndClassNameStr.Length > 0)
-                    System.IO.File.WriteAllText(appdatapath + "\\IPCClassName.dat", wndClassNameStr.ToString());
-            }
 
             Program.rootHub.Debug += On_Debug;
 

DS4Windows/Program.cs

@@ -6,11 +6,16 @@ using Process = System.Diagnostics.Process;
 using System.ComponentModel;
 using System.Globalization;
 using Microsoft.Win32.TaskScheduler;
+using System.IO.MemoryMappedFiles;
+using System.Text;
 
 namespace DS4Windows
 {
     static class Program
     {
+        [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
+        private static extern int GetClassName(IntPtr hWnd, StringBuilder lpClassName, int nMaxCount);
+
         [DllImport("user32.dll", EntryPoint = "FindWindow")]
         private static extern IntPtr FindWindow(string sClass, string sWindow);
 
@@ -36,6 +41,9 @@ namespace DS4Windows
         private static Thread controlThread;
         private static Form ds4form;
 
+        private static MemoryMappedFile ipcClassNameMMF = null; // MemoryMappedFile for inter-process communication used to hold className of DS4Form window
+        private static MemoryMappedViewAccessor ipcClassNameMMA = null;
+
         /// <summary>
         /// The main entry point for the application.
         /// </summary>
@@ -86,15 +94,14 @@ namespace DS4Windows
 
                     IntPtr hWndDS4WindowsForm = IntPtr.Zero;
 
-                    Global.FindConfigLocation();
+                    if (args[i].Length > 0 && args[i].Length <= 256)
-                    if (args[i].Length > 0 && args[i].Length <= 256 && !string.IsNullOrEmpty(Global.appdatapath) && System.IO.File.Exists(Global.appdatapath + "\\IPCClassName.dat"))
                     {
                         // Find the main DS4Form window handle and post WM_COPYDATA inter-process message. IPCClasName.dat file was created by the main DS4Windows process 
                         // and it contains the name of the DS4Form .NET window class name string (the hash key part of the string is dynamically generated by .NET engine and it may change,
                         // so that's why the main process re-creates the file if the window class name is changed by .NET framework). Finding the WND handle usig both class name and window name
                         // limits chances that WM_COPYDATA message is sent to a wrong window.
 
-                        hWndDS4WindowsForm = FindWindow(System.IO.File.ReadAllText(Global.appdatapath + "\\IPCClassName.dat"), "DS4Windows");
+                        hWndDS4WindowsForm = FindWindow(ReadIPCClassNameMMF(), "DS4Windows");
                         if (hWndDS4WindowsForm != IntPtr.Zero)
                         {
                             COPYDATASTRUCT cds;
@@ -178,6 +185,9 @@ namespace DS4Windows
             while (testThread.IsAlive)
                 Thread.SpinWait(500);
             threadComEvent.Close();
+
+            if (ipcClassNameMMA != null) ipcClassNameMMA.Dispose();
+            if (ipcClassNameMMF != null) ipcClassNameMMF.Dispose();
         }
 
         private static void createControlService()
@@ -233,5 +243,54 @@ namespace DS4Windows
                 temp.WindowState = FormWindowState.Normal;
             }
         }
+
+        public static void CreateIPCClassNameMMF(IntPtr hWnd)
+        {
+            if (ipcClassNameMMA != null) return; // Already holding a handle to MMF file. No need to re-write the data
+
+            try
+            {
+                StringBuilder wndClassNameStr = new StringBuilder(128);
+                if (GetClassName(hWnd, wndClassNameStr, wndClassNameStr.Capacity) != 0 && wndClassNameStr.Length > 0)
+                {
+                    byte[] buffer = ASCIIEncoding.ASCII.GetBytes(wndClassNameStr.ToString());
+
+                    ipcClassNameMMF = MemoryMappedFile.CreateNew("DS4Windows_IPCClassName.dat", 128);
+                    ipcClassNameMMA = ipcClassNameMMF.CreateViewAccessor(0, buffer.Length);
+                    ipcClassNameMMA.WriteArray(0, buffer, 0, buffer.Length);
+                    // The MMF file is alive as long this process holds the file handle open
+                }
+            }
+            catch (Exception)
+            {
+                /* Eat all exceptions because errors here are not fatal for DS4Win */
+            }
+        }
+
+        private static string ReadIPCClassNameMMF()
+        {
+            MemoryMappedFile mmf = null;
+            MemoryMappedViewAccessor mma = null;
+
+            try
+            {
+                byte[] buffer = new byte[128];
+                mmf = MemoryMappedFile.OpenExisting("DS4Windows_IPCClassName.dat");
+                mma = mmf.CreateViewAccessor(0, 128);
+                mma.ReadArray(0, buffer, 0, buffer.Length);
+                return ASCIIEncoding.ASCII.GetString(buffer);
+            }
+            catch (Exception)
+            {
+                // Eat all exceptions                
+            }
+            finally
+            {
+                if (mma != null) mma.Dispose();
+                if (mmf != null) mmf.Dispose();
+            }
+
+            return null;
+        }
     }
 }