Add native checksums.

Native.cs

@@ -0,0 +1,83 @@
+// /***************************************************************************
+// Aaru Data Preservation Suite
+// ----------------------------------------------------------------------------
+//
+// Filename       : Native.cs
+// Author(s)      : Natalia Portillo <claunia@claunia.com>
+//
+// Component      : Checksums.
+//
+// --[ Description ] ----------------------------------------------------------
+//
+//     Checks that Aaru.Checksums.Native library is available and usable.
+//
+// --[ 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 © 2011-2021 Natalia Portillo
+// ****************************************************************************/
+
+using System.Runtime.InteropServices;
+
+namespace Aaru.Checksums
+{
+    public static class Native
+    {
+        static bool _checked;
+        static bool _supported;
+
+        /// <summary>Set to return native as never supported</summary>
+        public static bool ForceManaged { get; set; }
+
+        /// <summary>
+        ///     If set to <c>true</c> the native library was found and loaded correctly and its reported version is
+        ///     compatible.
+        /// </summary>
+        public static bool IsSupported
+        {
+            get
+            {
+                if(ForceManaged)
+                    return false;
+
+                if(_checked)
+                    return _supported;
+
+                ulong version;
+                _checked = true;
+
+                try
+                {
+                    version = get_acn_version();
+                }
+                catch
+                {
+                    _supported = false;
+
+                    return false;
+                }
+
+                // TODO: Check version compatibility
+                _supported = version >= 0x06000000;
+
+                return _supported;
+            }
+        }
+
+        [DllImport("libAaru.Checksums.Native", SetLastError = true)]
+        static extern ulong get_acn_version();
+    }
+}