{-# LANGUAGE
    BangPatterns
  , UnicodeSyntax
  #-}
module Codec.Audio.WavPack.Unpack
    (
    )
    where
import Codec.Audio.WavPack.Internal
import Data.Bits
import Data.Bitstream.Generic (Bitstream)
import qualified Data.Bitstream.Generic as B
import Data.Word

-- Read a single unsigned value from the specified bitstream with a
-- value from 0 to maxCode. If there are exactly a power of two number
-- of possible codes then this will read a fixed number of bits;
-- otherwise it reads the minimum number of bits and then determines
-- whether another bit is needed to define the code.
readCode ∷ Bitstream bs ⇒ bs → Word32 → (Word32, bs)
{-# INLINEABLE readCode #-}
readCode bs 0       = (0, bs)
readCode bs 1       = (b2n $ B.head bs, B.tail bs)
readCode bs maxCode
    = let !bitCount = countBits maxCode
          !extras   = (1 `shiftL` bitCount) - maxCode - 1
      in
        error "unk"