open Types

let crc_lookup = [|
  0x00000000L;0x04c11db7L;0x09823b6eL;0x0d4326d9L;
  0x130476dcL;0x17c56b6bL;0x1a864db2L;0x1e475005L;
  0x2608edb8L;0x22c9f00fL;0x2f8ad6d6L;0x2b4bcb61L;
  0x350c9b64L;0x31cd86d3L;0x3c8ea00aL;0x384fbdbdL;
  0x4c11db70L;0x48d0c6c7L;0x4593e01eL;0x4152fda9L;
  0x5f15adacL;0x5bd4b01bL;0x569796c2L;0x52568b75L;
  0x6a1936c8L;0x6ed82b7fL;0x639b0da6L;0x675a1011L;
  0x791d4014L;0x7ddc5da3L;0x709f7b7aL;0x745e66cdL;
  0x9823b6e0L;0x9ce2ab57L;0x91a18d8eL;0x95609039L;
  0x8b27c03cL;0x8fe6dd8bL;0x82a5fb52L;0x8664e6e5L;
  0xbe2b5b58L;0xbaea46efL;0xb7a96036L;0xb3687d81L;
  0xad2f2d84L;0xa9ee3033L;0xa4ad16eaL;0xa06c0b5dL;
  0xd4326d90L;0xd0f37027L;0xddb056feL;0xd9714b49L;
  0xc7361b4cL;0xc3f706fbL;0xceb42022L;0xca753d95L;
  0xf23a8028L;0xf6fb9d9fL;0xfbb8bb46L;0xff79a6f1L;
  0xe13ef6f4L;0xe5ffeb43L;0xe8bccd9aL;0xec7dd02dL;
  0x34867077L;0x30476dc0L;0x3d044b19L;0x39c556aeL;
  0x278206abL;0x23431b1cL;0x2e003dc5L;0x2ac12072L;
  0x128e9dcfL;0x164f8078L;0x1b0ca6a1L;0x1fcdbb16L;
  0x018aeb13L;0x054bf6a4L;0x0808d07dL;0x0cc9cdcaL;
  0x7897ab07L;0x7c56b6b0L;0x71159069L;0x75d48ddeL;
  0x6b93dddbL;0x6f52c06cL;0x6211e6b5L;0x66d0fb02L;
  0x5e9f46bfL;0x5a5e5b08L;0x571d7dd1L;0x53dc6066L;
  0x4d9b3063L;0x495a2dd4L;0x44190b0dL;0x40d816baL;
  0xaca5c697L;0xa864db20L;0xa527fdf9L;0xa1e6e04eL;
  0xbfa1b04bL;0xbb60adfcL;0xb6238b25L;0xb2e29692L;
  0x8aad2b2fL;0x8e6c3698L;0x832f1041L;0x87ee0df6L;
  0x99a95df3L;0x9d684044L;0x902b669dL;0x94ea7b2aL;
  0xe0b41de7L;0xe4750050L;0xe9362689L;0xedf73b3eL;
  0xf3b06b3bL;0xf771768cL;0xfa325055L;0xfef34de2L;
  0xc6bcf05fL;0xc27dede8L;0xcf3ecb31L;0xcbffd686L;
  0xd5b88683L;0xd1799b34L;0xdc3abdedL;0xd8fba05aL;
  0x690ce0eeL;0x6dcdfd59L;0x608edb80L;0x644fc637L;
  0x7a089632L;0x7ec98b85L;0x738aad5cL;0x774bb0ebL;
  0x4f040d56L;0x4bc510e1L;0x46863638L;0x42472b8fL;
  0x5c007b8aL;0x58c1663dL;0x558240e4L;0x51435d53L;
  0x251d3b9eL;0x21dc2629L;0x2c9f00f0L;0x285e1d47L;
  0x36194d42L;0x32d850f5L;0x3f9b762cL;0x3b5a6b9bL;
  0x0315d626L;0x07d4cb91L;0x0a97ed48L;0x0e56f0ffL;
  0x1011a0faL;0x14d0bd4dL;0x19939b94L;0x1d528623L;
  0xf12f560eL;0xf5ee4bb9L;0xf8ad6d60L;0xfc6c70d7L;
  0xe22b20d2L;0xe6ea3d65L;0xeba91bbcL;0xef68060bL;
  0xd727bbb6L;0xd3e6a601L;0xdea580d8L;0xda649d6fL;
  0xc423cd6aL;0xc0e2d0ddL;0xcda1f604L;0xc960ebb3L;
  0xbd3e8d7eL;0xb9ff90c9L;0xb4bcb610L;0xb07daba7L;
  0xae3afba2L;0xaafbe615L;0xa7b8c0ccL;0xa379dd7bL;
  0x9b3660c6L;0x9ff77d71L;0x92b45ba8L;0x9675461fL;
  0x8832161aL;0x8cf30badL;0x81b02d74L;0x857130c3L;
  0x5d8a9099L;0x594b8d2eL;0x5408abf7L;0x50c9b640L;
  0x4e8ee645L;0x4a4ffbf2L;0x470cdd2bL;0x43cdc09cL;
  0x7b827d21L;0x7f436096L;0x7200464fL;0x76c15bf8L;
  0x68860bfdL;0x6c47164aL;0x61043093L;0x65c52d24L;
  0x119b4be9L;0x155a565eL;0x18197087L;0x1cd86d30L;
  0x029f3d35L;0x065e2082L;0x0b1d065bL;0x0fdc1becL;
  0x3793a651L;0x3352bbe6L;0x3e119d3fL;0x3ad08088L;
  0x2497d08dL;0x2056cd3aL;0x2d15ebe3L;0x29d4f654L;
  0xc5a92679L;0xc1683bceL;0xcc2b1d17L;0xc8ea00a0L;
  0xd6ad50a5L;0xd26c4d12L;0xdf2f6bcbL;0xdbee767cL;
  0xe3a1cbc1L;0xe760d676L;0xea23f0afL;0xeee2ed18L;
  0xf0a5bd1dL;0xf464a0aaL;0xf9278673L;0xfde69bc4L;
  0x89b8fd09L;0x8d79e0beL;0x803ac667L;0x84fbdbd0L;
  0x9abc8bd5L;0x9e7d9662L;0x933eb0bbL;0x97ffad0cL;
  0xafb010b1L;0xab710d06L;0xa6322bdfL;0xa2f33668L;
  0xbcb4666dL;0xb8757bdaL;0xb5365d03L;0xb1f740b4L |];;

let crc_iter crc v = 
    Int64.logxor
      (Int64.logand (Int64.shift_left crc 8) 0xFFFFFFFFL)
      (crc_lookup.(Int64.to_int(
        Int64.logxor 
          (Int64.logand (Int64.shift_right crc 24) 0xFFL) 
          (Int64.of_int v)))) ;;
  

let crc st = 
  let crc = ref 0L in
  let iterfun v = crc := crc_iter !crc (Char.code v) in
  String.iter iterfun st; Types.int64_to_oogg32 !crc;;