Crc.hs

module Rattletrap.Utility.Crc where

import qualified Data.Array.Unboxed as Array
import qualified Data.Bits as Bits
import qualified Data.ByteString as ByteString
import qualified Data.Word as Word

-- | Computes the CRC32 of some bytes. This is done to ensure that the bytes
-- are valid before trying to parse them.
--
-- @
-- compute ('Data.ByteString.Lazy.pack' [0x00])
-- @
--
-- This CRC uses an initial value of @0xefcbf201@ and a polynomial of
-- @0x04c11db7@.
compute :: ByteString.ByteString -> Word.Word32
compute = Bits.complement . ByteString.foldl' update initial

update :: Word.Word32 -> Word.Word8 -> Word.Word32
update crc byte =
  let index = Bits.xor byte . unsafeWord32ToWord8 $ Bits.shiftR crc 24
      left = table Array.! index
      right = Bits.shiftL crc 8
   in Bits.xor left right

unsafeWord32ToWord8 :: Word.Word32 -> Word.Word8
unsafeWord32ToWord8 = fromIntegral

initial :: Word.Word32
initial = Bits.complement 0xefcbf201

table :: Array.Array Word.Word8 Word.Word32
table =
  Array.listArray
    (0, 255)
    [ 0x00000000,
      0x04c11db7,
      0x09823b6e,
      0x0d4326d9,
      0x130476dc,
      0x17c56b6b,
      0x1a864db2,
      0x1e475005,
      0x2608edb8,
      0x22c9f00f,
      0x2f8ad6d6,
      0x2b4bcb61,
      0x350c9b64,
      0x31cd86d3,
      0x3c8ea00a,
      0x384fbdbd,
      0x4c11db70,
      0x48d0c6c7,
      0x4593e01e,
      0x4152fda9,
      0x5f15adac,
      0x5bd4b01b,
      0x569796c2,
      0x52568b75,
      0x6a1936c8,
      0x6ed82b7f,
      0x639b0da6,
      0x675a1011,
      0x791d4014,
      0x7ddc5da3,
      0x709f7b7a,
      0x745e66cd,
      0x9823b6e0,
      0x9ce2ab57,
      0x91a18d8e,
      0x95609039,
      0x8b27c03c,
      0x8fe6dd8b,
      0x82a5fb52,
      0x8664e6e5,
      0xbe2b5b58,
      0xbaea46ef,
      0xb7a96036,
      0xb3687d81,
      0xad2f2d84,
      0xa9ee3033,
      0xa4ad16ea,
      0xa06c0b5d,
      0xd4326d90,
      0xd0f37027,
      0xddb056fe,
      0xd9714b49,
      0xc7361b4c,
      0xc3f706fb,
      0xceb42022,
      0xca753d95,
      0xf23a8028,
      0xf6fb9d9f,
      0xfbb8bb46,
      0xff79a6f1,
      0xe13ef6f4,
      0xe5ffeb43,
      0xe8bccd9a,
      0xec7dd02d,
      0x34867077,
      0x30476dc0,
      0x3d044b19,
      0x39c556ae,
      0x278206ab,
      0x23431b1c,
      0x2e003dc5,
      0x2ac12072,
      0x128e9dcf,
      0x164f8078,
      0x1b0ca6a1,
      0x1fcdbb16,
      0x018aeb13,
      0x054bf6a4,
      0x0808d07d,
      0x0cc9cdca,
      0x7897ab07,
      0x7c56b6b0,
      0x71159069,
      0x75d48dde,
      0x6b93dddb,
      0x6f52c06c,
      0x6211e6b5,
      0x66d0fb02,
      0x5e9f46bf,
      0x5a5e5b08,
      0x571d7dd1,
      0x53dc6066,
      0x4d9b3063,
      0x495a2dd4,
      0x44190b0d,
      0x40d816ba,
      0xaca5c697,
      0xa864db20,
      0xa527fdf9,
      0xa1e6e04e,
      0xbfa1b04b,
      0xbb60adfc,
      0xb6238b25,
      0xb2e29692,
      0x8aad2b2f,
      0x8e6c3698,
      0x832f1041,
      0x87ee0df6,
      0x99a95df3,
      0x9d684044,
      0x902b669d,
      0x94ea7b2a,
      0xe0b41de7,
      0xe4750050,
      0xe9362689,
      0xedf73b3e,
      0xf3b06b3b,
      0xf771768c,
      0xfa325055,
      0xfef34de2,
      0xc6bcf05f,
      0xc27dede8,
      0xcf3ecb31,
      0xcbffd686,
      0xd5b88683,
      0xd1799b34,
      0xdc3abded,
      0xd8fba05a,
      0x690ce0ee,
      0x6dcdfd59,
      0x608edb80,
      0x644fc637,
      0x7a089632,
      0x7ec98b85,
      0x738aad5c,
      0x774bb0eb,
      0x4f040d56,
      0x4bc510e1,
      0x46863638,
      0x42472b8f,
      0x5c007b8a,
      0x58c1663d,
      0x558240e4,
      0x51435d53,
      0x251d3b9e,
      0x21dc2629,
      0x2c9f00f0,
      0x285e1d47,
      0x36194d42,
      0x32d850f5,
      0x3f9b762c,
      0x3b5a6b9b,
      0x0315d626,
      0x07d4cb91,
      0x0a97ed48,
      0x0e56f0ff,
      0x1011a0fa,
      0x14d0bd4d,
      0x19939b94,
      0x1d528623,
      0xf12f560e,
      0xf5ee4bb9,
      0xf8ad6d60,
      0xfc6c70d7,
      0xe22b20d2,
      0xe6ea3d65,
      0xeba91bbc,
      0xef68060b,
      0xd727bbb6,
      0xd3e6a601,
      0xdea580d8,
      0xda649d6f,
      0xc423cd6a,
      0xc0e2d0dd,
      0xcda1f604,
      0xc960ebb3,
      0xbd3e8d7e,
      0xb9ff90c9,
      0xb4bcb610,
      0xb07daba7,
      0xae3afba2,
      0xaafbe615,
      0xa7b8c0cc,
      0xa379dd7b,
      0x9b3660c6,
      0x9ff77d71,
      0x92b45ba8,
      0x9675461f,
      0x8832161a,
      0x8cf30bad,
      0x81b02d74,
      0x857130c3,
      0x5d8a9099,
      0x594b8d2e,
      0x5408abf7,
      0x50c9b640,
      0x4e8ee645,
      0x4a4ffbf2,
      0x470cdd2b,
      0x43cdc09c,
      0x7b827d21,
      0x7f436096,
      0x7200464f,
      0x76c15bf8,
      0x68860bfd,
      0x6c47164a,
      0x61043093,
      0x65c52d24,
      0x119b4be9,
      0x155a565e,
      0x18197087,
      0x1cd86d30,
      0x029f3d35,
      0x065e2082,
      0x0b1d065b,
      0x0fdc1bec,
      0x3793a651,
      0x3352bbe6,
      0x3e119d3f,
      0x3ad08088,
      0x2497d08d,
      0x2056cd3a,
      0x2d15ebe3,
      0x29d4f654,
      0xc5a92679,
      0xc1683bce,
      0xcc2b1d17,
      0xc8ea00a0,
      0xd6ad50a5,
      0xd26c4d12,
      0xdf2f6bcb,
      0xdbee767c,
      0xe3a1cbc1,
      0xe760d676,
      0xea23f0af,
      0xeee2ed18,
      0xf0a5bd1d,
      0xf464a0aa,
      0xf9278673,
      0xfde69bc4,
      0x89b8fd09,
      0x8d79e0be,
      0x803ac667,
      0x84fbdbd0,
      0x9abc8bd5,
      0x9e7d9662,
      0x933eb0bb,
      0x97ffad0c,
      0xafb010b1,
      0xab710d06,
      0xa6322bdf,
      0xa2f33668,
      0xbcb4666d,
      0xb8757bda,
      0xb5365d03,
      0xb1f740b4
    ]