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module Base58 where
import qualified Crypto.Hash.SHA256 as SHA256
import qualified Data.ByteString as S
import Data.Maybe
import Data.List
import Data.Word ( Word8 )
import Control.Monad
base58chars :: [Char]
base58chars = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
base58digits :: [Char] -> Maybe [Int]
base58digits str = sequence mbs
where
mbs = map (flip elemIndex base58chars) str
-- 5HueCGU8rMjxEXxiPuD5BDku4MkFqeZyd4dZ1jvhTVqvbTLvyTJ
base58_decode :: [Char] -> Maybe (Word8,[Word8])
base58_decode str = do
ds <- base58digits str
let n = foldl' (\a b-> a*58 + b) 0 $ ( map fromIntegral ds :: [Integer] )
rbytes = unfoldr getbyte n
getbyte d = do
guard (d/=0)
let (q,b) = d `divMod` 256
return (fromIntegral b,q)
let (rcksum,rpayload) = splitAt 4 $ rbytes
a_payload = reverse rpayload
hash_result = S.take 4 . SHA256.hash . SHA256.hash . S.pack $ a_payload
expected_hash = S.pack $ reverse rcksum
(network_id,payload) = splitAt 1 a_payload
network_id <- listToMaybe network_id
guard (hash_result==expected_hash)
return (network_id,payload)
base58_encode :: S.ByteString -> String
base58_encode hash = replicate zcount '1' ++ map (base58chars !!) (reverse rdigits)
where
zcount = S.length . S.takeWhile (==0) $ hash
cksum = S.take 4 . SHA256.hash . SHA256.hash $ hash
n = foldl' (\a b->a*256+b) 0 . map asInteger $ concatMap S.unpack [hash, cksum]
asInteger x = fromIntegral x :: Integer
rdigits = unfoldr getdigit n
where
getdigit d = do
guard (d/=0)
let (q,b) = d `divMod` 58
return (fromIntegral b,q)
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