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{-# LANGUAGE Trustworthy #-}
{-# LANGUAGE NoImplicitPrelude #-}
-- ----------------------------------------------------------------------------
--
-- (c) The University of Glasgow 2006
--
-- Fingerprints for recompilation checking and ABI versioning, and
-- implementing fast comparison of Typeable.
--
-- ----------------------------------------------------------------------------
module GHC.Fingerprint.Type (Fingerprint(..)) where
import GHC.Base
import GHC.List (length, replicate)
import GHC.Num
import GHC.Show
import GHC.Word
import Numeric (showHex)
-- Using 128-bit MD5 fingerprints for now.
data Fingerprint = Fingerprint {-# UNPACK #-} !Word64 {-# UNPACK #-} !Word64
deriving ( Eq -- ^ @since 4.4.0.0
, Ord -- ^ @since 4.4.0.0
)
-- | @since 4.7.0.0
instance Show Fingerprint where
show (Fingerprint w1 w2) = hex16 w1 ++ hex16 w2
where
-- | Formats a 64 bit number as 16 digits hex.
hex16 :: Word64 -> String
hex16 i = let hex = showHex i ""
in replicate (16 - length hex) '0' ++ hex
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