{-# LANGUAGE BinaryLiterals #-}

module Octane.Utility.Endian
  ( reverseBitsInStrictBytes
  ) where

import qualified Data.Bits as Bits
import qualified Data.ByteString as StrictBytes
import qualified Data.Word as Word

-- | Reverses all the bits in each strict byte.
reverseBitsInStrictBytes :: StrictBytes.ByteString -> StrictBytes.ByteString
reverseBitsInStrictBytes bytes = StrictBytes.map reverseBits bytes

reverseBits :: Word.Word8 -> Word.Word8
reverseBits byte =
  Bits.shiftR (byte Bits..&. 0b10000000) 7 +
  Bits.shiftR (byte Bits..&. 0b01000000) 5 +
  Bits.shiftR (byte Bits..&. 0b00100000) 3 +
  Bits.shiftR (byte Bits..&. 0b00010000) 1 +
  Bits.shiftL (byte Bits..&. 0b00001000) 1 +
  Bits.shiftL (byte Bits..&. 0b00000100) 3 +
  Bits.shiftL (byte Bits..&. 0b00000010) 5 +
  Bits.shiftL (byte Bits..&. 0b00000001) 7