-- Copyright 2017 Google LLC
--
-- Licensed under the Apache License, Version 2.0 (the "License"); you may not
-- use this file except in compliance with the License. You may obtain a copy of
-- the License at
--
--     https://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
-- WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
-- License for the specific language governing permissions and limitations under
-- the License.

module Data.Digest.Internal where

import Data.Bits (Bits((.&.)), shiftR)
import Data.ByteString (ByteString)
import qualified Data.ByteString as ByteString
import Data.Char (intToDigit)
import Data.Word (Word8)
import Foreign (Ptr)

import Internal.Base (EvpMd)

-- | A cryptographic hash function.
newtype Algorithm = Algorithm (Ptr EvpMd)

-- | The result of a hash operation.
newtype Digest =
  Digest ByteString
  deriving (Eq, Ord)

instance Show Digest where
  show (Digest d) = ByteString.foldr showHexPadded [] d
    where
      showHexPadded b xs =
        hexit (b `shiftR` 4 .&. 0x0f) : hexit (b .&. 0x0f) : xs
      hexit = intToDigit . fromIntegral :: Word8 -> Char