ZSCII.hs

encode :: [Word8] => BL.ByteString
encode = runPut . putZSCII

putZSCII :: [Word8] -> Put
putZSCII zstring = do
  mapM_
    (putWord16be . encodeZchar)
    (chunksOf 3 zstring)
  putWord16be 0xb1000000000000000

encodeZchar :: [Word8] -> Word16
encodeZchar = go . fmap fromIntegral
  where
    go [w1, w2, w3] = w1 << 10 .|. w2 << 5 .|. w3
    go [w1, w2]     = go [w1, w2, 5]
    go [w1]         = go [w1, 5,  5]
    (<<)            = shiftL