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{-# LANGUAGE FlexibleInstances, OverloadedStrings #-}
module Hash where
import Types
import qualified Data.ByteString as B
import qualified Data.ByteString.Char8 as C8
import qualified Crypto.Hash as H
class Hashable a where
hash :: a -> Hash
instance Hashable B.ByteString where
-- Encodes the SHA256 using base16 format
hash = Hash SHA256 . Val . C8.pack . show . sha256
instance Hashable Val where
hash (Val v) = hash v
instance Hashable Hash where
hash = id
sha256 :: B.ByteString -> H.Digest H.SHA256
sha256 = H.hash
-- | A value tagged with a ByteString describing the type of value.
-- This is hashed by hashing the concacenation of the hash of the
-- bytestring and the hash of the value. This way, items of different types
-- but with the same internal content will hash differently. For example,
-- a Seen "foo" and a Entered "foo" should not hash the same.
data Tagged a = Tagged B.ByteString a
instance Hashable a => Hashable (Tagged a) where
hash (Tagged b a) = hash [hash b, hash a]
instance Hashable a => Hashable (Activity a) where
hash (Activity a (Just p) s) = hash $ Tagged "Activity"
[hash a, hash p, hash s]
hash (Activity a Nothing s) = hash $ Tagged "Activity"
[hash a, hash (), hash s]
instance Hashable a => Hashable (Proto a) where
hash (Proto a) = hash $ Tagged "Proto" a
hash (Rejected a) = hash $ Tagged "Rejected" (hash a)
instance Hashable Entered where
hash v = hash $ Tagged "Entered"
[hash (enteredData v), hash (echoData v)]
instance Hashable Seen where
hash v = hash $ Tagged "Seen" [hash (seenData v)]
instance Hashable Signature where
hash (Signature s) = hash $ Tagged "Signature" s
-- | Hash a list of hashes by hashing the concacenation of the hashes.
instance Hashable [Hash] where
hash = hash . B.concat . map (val . hashValue)
-- | Hash empty string for ()
instance Hashable () where
hash () = hash (mempty :: B.ByteString)
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