Grafx2 now disables safety backups (and warns the user on startup) if another instance is running or if its configuration directory is read-only. Implemented separately on Linux and Windows, tested only on Windows

git-svn-id: svn://pulkomandy.tk/GrafX2/trunk@1343 416bcca6-2ee7-4201-b75f-2eb2f807beb1

io.c

@@ -284,3 +284,72 @@ void Get_full_filename(char * output_name, char * file_name, char * directory_na
   }
   strcat(output_name,file_name);
 }
+
+/// Lock file used to prevent several instances of grafx2 from harming each others' backups
+#ifdef __WIN32__
+HANDLE Lock_file_handle = INVALID_HANDLE_VALUE;
+#else
+int Lock_file_handle = -1;
+#endif
+
+byte Create_lock_file(const char *file_directory)
+{
+  char lock_filename[MAX_PATH_CHARACTERS];
+  
+  strcpy(lock_filename,file_directory);
+  strcat(lock_filename,"gfx2.lck");
+  
+  #ifdef __WIN32__
+  // Windowzy method for creating a lock file
+  Lock_file_handle = CreateFile(
+    lock_filename,
+    GENERIC_WRITE,
+    0, // No sharing
+    NULL,
+    OPEN_ALWAYS,
+    FILE_ATTRIBUTE_NORMAL,
+    NULL);
+  if (Lock_file_handle == INVALID_HANDLE_VALUE)
+  {
+    return -1;
+  }
+  #else
+  // Unixy method for lock file
+  Lock_file_handle = open(lock_filename,O_WRONLY|O_CREAT);
+  if (Lock_file_handle == -1)
+  {
+    // Usually write-protected media
+    return -1;
+  }
+  if (lockf(Lock_file_handle, F_TLOCK, 0)==-1)
+  {
+    close(Lock_file_handle);
+    // Usually write-protected media
+    return -1;
+  }
+  #endif
+  return 0;
+}
+
+void Release_lock_file(const char *file_directory)
+{
+  char lock_filename[MAX_PATH_CHARACTERS];
+    
+  #ifdef __WIN32__
+  if (Lock_file_handle != INVALID_HANDLE_VALUE)
+  {
+    CloseHandle(Lock_file_handle);
+  }
+  #else
+  if (Lock_file_handle != -1)
+  {
+    close(Lock_file_handle);
+    Lock_file_handle = -1;
+  }  
+  #endif
+  
+  // Actual deletion
+  strcpy(lock_filename,file_directory);
+  strcat(lock_filename,"gfx2.lck");
+  remove(lock_filename);
+}