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|
module Number.Serialize
( i2osp
, os2ip
, lengthBytes
) where
import Data.ByteString (ByteString)
import qualified Data.ByteString as B
import Data.Bits
-- | os2ip converts a byte string into a positive integer
os2ip :: ByteString -> Integer
os2ip = B.foldl' (\a b -> (256 * a) .|. (fromIntegral b)) 0
-- | i2osp converts a positive integer into a byte string
i2osp :: Integer -> ByteString
i2osp m = B.reverse $ B.unfoldr divMod256 m
where
divMod256 0 = Nothing
divMod256 n = Just (fromIntegral a,b) where (b,a) = n `divMod` 256
-- | returns the number of bytes to store an integer with i2osp
lengthBytes :: Integer -> Int
lengthBytes n
| n < 256 = 1
| otherwise = 1 + lengthBytes (n `div` 256)
|
