Source file gin_crc32c.ml

(* Copyright (c) 2011, Jonathan Derque - MIT licensed *)
(* Copyright (c) 2016, Gabriel de Perthuis - MIT licensed *)

type t = Optint.t

let (&&&) = Optint.logand
let (^^^) = Optint.logxor
let (>>>) = Optint.shift_right_logical
let ffffffff = Optint.(succ (mul max_int (of_int 2)))
let (~~~) x = Optint.((logand (lognot x) ffffffff))

let crc_table = Array.map Optint.of_int32 [|
    0x00000000l; 0xf26b8303l; 0xe13b70f7l; 0x1350f3f4l;
    0xc79a971fl; 0x35f1141cl; 0x26a1e7e8l; 0xd4ca64ebl;
    0x8ad958cfl; 0x78b2dbccl; 0x6be22838l; 0x9989ab3bl;
    0x4d43cfd0l; 0xbf284cd3l; 0xac78bf27l; 0x5e133c24l;
    0x105ec76fl; 0xe235446cl; 0xf165b798l; 0x030e349bl;
    0xd7c45070l; 0x25afd373l; 0x36ff2087l; 0xc494a384l;
    0x9a879fa0l; 0x68ec1ca3l; 0x7bbcef57l; 0x89d76c54l;
    0x5d1d08bfl; 0xaf768bbcl; 0xbc267848l; 0x4e4dfb4bl;
    0x20bd8edel; 0xd2d60dddl; 0xc186fe29l; 0x33ed7d2al;
    0xe72719c1l; 0x154c9ac2l; 0x061c6936l; 0xf477ea35l;
    0xaa64d611l; 0x580f5512l; 0x4b5fa6e6l; 0xb93425e5l;
    0x6dfe410el; 0x9f95c20dl; 0x8cc531f9l; 0x7eaeb2fal;
    0x30e349b1l; 0xc288cab2l; 0xd1d83946l; 0x23b3ba45l;
    0xf779deael; 0x05125dadl; 0x1642ae59l; 0xe4292d5al;
    0xba3a117el; 0x4851927dl; 0x5b016189l; 0xa96ae28al;
    0x7da08661l; 0x8fcb0562l; 0x9c9bf696l; 0x6ef07595l;
    0x417b1dbcl; 0xb3109ebfl; 0xa0406d4bl; 0x522bee48l;
    0x86e18aa3l; 0x748a09a0l; 0x67dafa54l; 0x95b17957l;
    0xcba24573l; 0x39c9c670l; 0x2a993584l; 0xd8f2b687l;
    0x0c38d26cl; 0xfe53516fl; 0xed03a29bl; 0x1f682198l;
    0x5125dad3l; 0xa34e59d0l; 0xb01eaa24l; 0x42752927l;
    0x96bf4dccl; 0x64d4cecfl; 0x77843d3bl; 0x85efbe38l;
    0xdbfc821cl; 0x2997011fl; 0x3ac7f2ebl; 0xc8ac71e8l;
    0x1c661503l; 0xee0d9600l; 0xfd5d65f4l; 0x0f36e6f7l;
    0x61c69362l; 0x93ad1061l; 0x80fde395l; 0x72966096l;
    0xa65c047dl; 0x5437877el; 0x4767748al; 0xb50cf789l;
    0xeb1fcbadl; 0x197448ael; 0x0a24bb5al; 0xf84f3859l;
    0x2c855cb2l; 0xdeeedfb1l; 0xcdbe2c45l; 0x3fd5af46l;
    0x7198540dl; 0x83f3d70el; 0x90a324fal; 0x62c8a7f9l;
    0xb602c312l; 0x44694011l; 0x5739b3e5l; 0xa55230e6l;
    0xfb410cc2l; 0x092a8fc1l; 0x1a7a7c35l; 0xe811ff36l;
    0x3cdb9bddl; 0xceb018del; 0xdde0eb2al; 0x2f8b6829l;
    0x82f63b78l; 0x709db87bl; 0x63cd4b8fl; 0x91a6c88cl;
    0x456cac67l; 0xb7072f64l; 0xa457dc90l; 0x563c5f93l;
    0x082f63b7l; 0xfa44e0b4l; 0xe9141340l; 0x1b7f9043l;
    0xcfb5f4a8l; 0x3dde77abl; 0x2e8e845fl; 0xdce5075cl;
    0x92a8fc17l; 0x60c37f14l; 0x73938ce0l; 0x81f80fe3l;
    0x55326b08l; 0xa759e80bl; 0xb4091bffl; 0x466298fcl;
    0x1871a4d8l; 0xea1a27dbl; 0xf94ad42fl; 0x0b21572cl;
    0xdfeb33c7l; 0x2d80b0c4l; 0x3ed04330l; 0xccbbc033l;
    0xa24bb5a6l; 0x502036a5l; 0x4370c551l; 0xb11b4652l;
    0x65d122b9l; 0x97baa1bal; 0x84ea524el; 0x7681d14dl;
    0x2892ed69l; 0xdaf96e6al; 0xc9a99d9el; 0x3bc21e9dl;
    0xef087a76l; 0x1d63f975l; 0x0e330a81l; 0xfc588982l;
    0xb21572c9l; 0x407ef1cal; 0x532e023el; 0xa145813dl;
    0x758fe5d6l; 0x87e466d5l; 0x94b49521l; 0x66df1622l;
    0x38cc2a06l; 0xcaa7a905l; 0xd9f75af1l; 0x2b9cd9f2l;
    0xff56bd19l; 0x0d3d3e1al; 0x1e6dcdeel; 0xec064eedl;
    0xc38d26c4l; 0x31e6a5c7l; 0x22b65633l; 0xd0ddd530l;
    0x0417b1dbl; 0xf67c32d8l; 0xe52cc12cl; 0x1747422fl;
    0x49547e0bl; 0xbb3ffd08l; 0xa86f0efcl; 0x5a048dffl;
    0x8ecee914l; 0x7ca56a17l; 0x6ff599e3l; 0x9d9e1ae0l;
    0xd3d3e1abl; 0x21b862a8l; 0x32e8915cl; 0xc083125fl;
    0x144976b4l; 0xe622f5b7l; 0xf5720643l; 0x07198540l;
    0x590ab964l; 0xab613a67l; 0xb831c993l; 0x4a5a4a90l;
    0x9e902e7bl; 0x6cfbad78l; 0x7fab5e8cl; 0x8dc0dd8fl;
    0xe330a81al; 0x115b2b19l; 0x020bd8edl; 0xf0605beel;
    0x24aa3f05l; 0xd6c1bc06l; 0xc5914ff2l; 0x37faccf1l;
    0x69e9f0d5l; 0x9b8273d6l; 0x88d28022l; 0x7ab90321l;
    0xae7367cal; 0x5c18e4c9l; 0x4f48173dl; 0xbd23943el;
    0xf36e6f75l; 0x0105ec76l; 0x12551f82l; 0xe03e9c81l;
    0x34f4f86al; 0xc69f7b69l; 0xd5cf889dl; 0x27a40b9el;
    0x79b737bal; 0x8bdcb4b9l; 0x988c474dl; 0x6ae7c44el;
    0xbe2da0a5l; 0x4c4623a6l; 0x5f16d052l; 0xad7d5351l;
|]

let buf_fold_left get f acc buf offset length =
  let acc_r = ref acc in
  for i = offset to offset + length - 1 do
    acc_r := f !acc_r (get buf i)
  done;
  !acc_r

let update_crc acc c =
  let index = (Optint.to_int acc lxor int_of_char c) land 0xff in
  (crc_table.(index) ^^^ (acc >>> 8)) &&& ffffffff

let crc32c : type a. get:(a -> int -> char) -> a -> int -> int -> t -> t
  = fun ~get buf off len crc ->
  ~~~(buf_fold_left get update_crc ~~~crc buf off len)

type bigstring = (char, Bigarray.int8_unsigned_elt, Bigarray.c_layout) Bigarray.Array1.t

let digest_bigstring =
  let get : bigstring -> int -> char = Bigarray.Array1.get in
  crc32c ~get

let digest_string =
  let get = String.get in
  crc32c ~get

let digest_bytes =
  let get = Bytes.get in
  crc32c ~get