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diff --git a/src/Text/Pandoc/Lua/Module/Utils.hs b/src/Text/Pandoc/Lua/Module/Utils.hs
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+{-
+Copyright © 2017 Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program 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 General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+-}
+{- |
+   Module      : Text.Pandoc.Lua.Module.Utils
+   Copyright   : Copyright © 2017 Albert Krewinkel
+   License     : GNU GPL, version 2 or above
+
+   Maintainer  : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
+   Stability   : alpha
+
+Utility module for lua, exposing internal helper functions.
+-}
+module Text.Pandoc.Lua.Module.Utils
+  ( pushModule
+  ) where
+
+import Data.Digest.Pure.SHA (sha1, showDigest)
+import Foreign.Lua (Lua, NumResults)
+import Text.Pandoc.Lua.StackInstances ()
+import Text.Pandoc.Lua.Util (addFunction)
+
+import qualified Data.ByteString.Lazy as BSL
+import qualified Foreign.Lua as Lua
+
+-- | Push the "pandoc.utils" module to the lua stack.
+pushModule :: Lua NumResults
+pushModule = do
+  Lua.newtable
+  addFunction "sha1" sha1HashFn
+  return 1
+
+-- | Calculate the hash of the given contents.
+sha1HashFn :: BSL.ByteString
+           -> Lua String
+sha1HashFn = return . showDigest . sha1