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+{- git-annex backend utilities
+ -
+ - Copyright 2012 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Backend.Utilities where
+
+import Data.Hash.MD5
+
+import Common.Annex
+
+{- Generates a keyName from an input string. Takes care of sanitizing it.
+ - If it's not too long, the full string is used as the keyName.
+ - Otherwise, it's truncated at half the filename length limit, and its
+ - md5 is prepended to ensure a unique key. -}
+genKeyName :: String -> Annex String
+genKeyName s = do
+	limit <- liftIO . fileNameLengthLimit =<< fromRepo gitAnnexDir
+	let s' = preSanitizeKeyName s
+	let truncs = truncateFilePath (limit `div` 2) s'
+	return $ if s' == truncs
+		then s'
+		else truncs ++ "-" ++ md5s (Str s)