Crc.hs

module Rattletrap.Utility.Crc
  ( compute
  ) where

import qualified Data.Array.Unboxed as Array
import qualified Data.Bits as Bits
import qualified Data.ByteString as Bytes
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 :: Bytes.ByteString -> Word.Word32
compute = Bits.complement . Bytes.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
  ]