// Copyright 2010 Google Inc. All Rights Reserved.

// Authors: jyrki@google.com (Jyrki Alakuijala), gpike@google.com (Geoff Pike)

#pragma once

#include "gutil/int128.h"

#include "gutil/integral_types.h"

// Hash 128 input bits down to 64 bits of output.

// This is intended to be a reasonably good hash function.

// It may change from time to time.

inline uint64 Hash128to64(const uint128& x) {

    // Murmur-inspired hashing.

    const uint64 kMul = 0xc6a4a7935bd1e995ULL;

    uint64 a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul;

    a ^= (a >> 47);

    uint64 b = (Uint128High64(x) ^ a) * kMul;

    b ^= (b >> 47);

    b *= kMul;

    return b;

}