0xDEADBEEF

CyclicHash.d

import core.bitop;
import std.random;

/* Massively simplified version of https://github.com/lemire/rollinghashcpp/blob/master/cyclichash.h by Daniel Lemire
   License: Apache 2.0 */
struct CyclicHash(HashT = uint) {

  HashT hash = 0;
  private uint n;

  HashT[1 << 8] table;

  this(uint _n, uint seed = 1337) {
    n = _n;
    auto rng = Random(seed);
    foreach (ref h; table) {
      h = uniform!HashT(rng);
    }
  }

  /* add inByte and remove outByte from the hash */
  void update(T : ubyte)(T outByte, T inByte) {
    hash = rol!1(hash) ^ rol(table[outByte], n) ^ table[inByte];
  }

  /* add byte to the hash, this is used at the start to initialize hash */
  void add(T : ubyte)(T b) {
    hash = rol!1(hash) ^ table[b];
  }

  void init(T : ubyte)(T[] bytes) {
    foreach (i; 0 .. n) {
      add(bytes[i]);
    }
  }

  void reset() {
    hash = 0;
  }
}