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|
-- |
-- Module : Crypto.Number.Serialize
-- License : BSD-style
-- Maintainer : Vincent Hanquez <vincent@snarc.org>
-- Stability : experimental
-- Portability : Good
--
-- Fast serialization primitives for integer
{-# LANGUAGE BangPatterns #-}
module Crypto.Number.Serialize
( i2osp
, os2ip
, i2ospOf
, i2ospOf_
) where
import Crypto.Number.Basic
import Crypto.Internal.Compat (unsafeDoIO)
import qualified Crypto.Internal.ByteArray as B
import qualified Crypto.Number.Serialize.Internal as Internal
-- | @os2ip@ converts a byte string into a positive integer.
os2ip :: B.ByteArrayAccess ba => ba -> Integer
os2ip bs = unsafeDoIO $ B.withByteArray bs (\p -> Internal.os2ip p (B.length bs))
-- | @i2osp@ converts a positive integer into a byte string.
--
-- The first byte is MSB (most significant byte); the last byte is the LSB (least significant byte)
i2osp :: B.ByteArray ba => Integer -> ba
i2osp 0 = B.allocAndFreeze 1 (\p -> Internal.i2osp 0 p 1 >> return ())
i2osp m = B.allocAndFreeze sz (\p -> Internal.i2osp m p sz >> return ())
where
!sz = numBytes m
-- | Just like 'i2osp', but takes an extra parameter for size.
-- If the number is too big to fit in @len@ bytes, 'Nothing' is returned
-- otherwise the number is padded with 0 to fit the @len@ required.
{-# INLINABLE i2ospOf #-}
i2ospOf :: B.ByteArray ba => Int -> Integer -> Maybe ba
i2ospOf len m
| len <= 0 = Nothing
| m < 0 = Nothing
| sz > len = Nothing
| otherwise = Just $ B.unsafeCreate len (\p -> Internal.i2ospOf m p len >> return ())
where
!sz = numBytes m
-- | Just like 'i2ospOf' except that it doesn't expect a failure: i.e.
-- an integer larger than the number of output bytes requested.
--
-- For example if you just took a modulo of the number that represent
-- the size (example the RSA modulo n).
i2ospOf_ :: B.ByteArray ba => Int -> Integer -> ba
i2ospOf_ len = maybe (error "i2ospOf_: integer is larger than expected") id . i2ospOf len
|
