Refactor image classes and split them to smaller files.

DiscImageChef.DiscImages/DiskCopy42/Helpers.cs

@@ -0,0 +1,52 @@
+// /***************************************************************************
+// The Disc Image Chef
+// ----------------------------------------------------------------------------
+//
+// Filename       : Helpers.cs
+// Author(s)      : Natalia Portillo <claunia@claunia.com>
+//
+// Component      : Disk image plugins.
+//
+// --[ Description ] ----------------------------------------------------------
+//
+//     Contains helpers for Apple DiskCopy 4.2 disk images.
+//
+// --[ License ] --------------------------------------------------------------
+//
+//     This library is free software; you can redistribute it and/or modify
+//     it under the terms of the GNU Lesser General Public License as
+//     published by the Free Software Foundation; either version 2.1 of the
+//     License, or (at your option) any later version.
+//
+//     This library is distributed in the hope that it will be useful, but
+//     WITHOUT ANY WARRANTY; without even the implied warranty of
+//     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+//     Lesser General Public License for more details.
+//
+//     You should have received a copy of the GNU Lesser General Public
+//     License along with this library; if not, see <http://www.gnu.org/licenses/>.
+//
+// ----------------------------------------------------------------------------
+// Copyright © 2011-2018 Natalia Portillo
+// ****************************************************************************/
+
+namespace DiscImageChef.DiscImages
+{
+    public partial class DiskCopy42
+    {
+        static uint DC42CheckSum(byte[] buffer)
+        {
+            uint dc42Chk = 0;
+            if((buffer.Length & 0x01) == 0x01) return 0xFFFFFFFF;
+
+            for(uint i = 0; i < buffer.Length; i += 2)
+            {
+                dc42Chk += (uint)(buffer[i] << 8);
+                dc42Chk += buffer[i + 1];
+                dc42Chk =  (dc42Chk >> 1) | (dc42Chk << 31);
+            }
+
+            return dc42Chk;
+        }
+    }
+}