Add SHA256 calculator

Based on the sha256c.c file from the FreeBSD project and ported to compile on
Linux, Mac OS, and Windows. The file is licensed under the simplified/2-clause
BSD license so the library is now MIT/BSD-licensed.

1 files changed, 6 insertions, 0 deletions

diff --git a/LICENSE b/LICENSE
index ec7646c..0579b2b 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,3 +1,9 @@
+butl/sha256c.c:
+
+2-clause BSD, see the file header for details.
+
+The rest:
+
 Copyright (c) 2014-2016 Code Synthesis Ltd
 
 Permission is hereby granted, free of charge, to any person obtaining