// Copyright (c) 2011 Google, Inc.

//

// Permission is hereby granted, free of charge, to any person obtaining a copy

// of this software and associated documentation files (the "Software"), to deal

// in the Software without restriction, including without limitation the rights

// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

// copies of the Software, and to permit persons to whom the Software is

// furnished to do so, subject to the following conditions:

//

// The above copyright notice and this permission notice shall be included in

// all copies or substantial portions of the Software.

//

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

// THE SOFTWARE.

//

// CityHash Version 1, by Geoff Pike and Jyrki Alakuijala

//

// This file provides a few functions for hashing strings. On x86-64

// hardware in 2011, CityHash64() is faster than other high-quality

// hash functions, such as Murmur.  This is largely due to higher

// instruction-level parallelism.  CityHash64() and CityHash128() also perform

// well on hash-quality tests.

//

// CityHash128() is optimized for relatively long strings and returns

// a 128-bit hash.  For strings more than about 2000 bytes it can be

// faster than CityHash64().

//

// Functions in the CityHash family are not suitable for cryptography.

//

// WARNING: This code has not been tested on big-endian platforms!

// It is known to work well on little-endian platforms that have a small penalty

// for unaligned reads, such as current Intel and AMD moderate-to-high-end CPUs.

//

// By the way, for some hash functions, given strings a and b, the hash

// of a+b is easily derived from the hashes of a and b.  This property

// doesn't hold for any hash functions in this file.

#ifndef CITY_HASH_H_

#define CITY_HASH_H_

#include <stdlib.h>  // for size_t.

#include <stdint.h>

typedef uint8_t uint8;

typedef uint32_t uint32;

typedef uint64_t uint64;

// The standard <utility> header doesn't compile, apparently it conflicts

// with... some Mozilla something or other. But all that's used from it

// is std::pair, so we can just replace that with mozilla::Pair.

#ifndef MOZILLA_CLIENT

#include <utility>

typedef std::pair<uint64, uint64> uint128;

inline uint64 Uint128Low64(const uint128& x) { return x.first; }

inline uint64 Uint128High64(const uint128& x) { return x.second; }

#else

#include "mozilla/Pair.h"

typedef mozilla::Pair<uint64, uint64> uint128;

inline uint64 Uint128Low64(const uint128& x) { return x.first(); }

inline uint64 Uint128High64(const uint128& x) { return x.second(); }

#endif

// Hash function for a byte array.

uint64 CityHash64(const char *buf, size_t len);

// Hash function for a byte array.  For convenience, a 64-bit seed is also

// hashed into the result.

uint64 CityHash64WithSeed(const char *buf, size_t len, uint64 seed);

// Hash function for a byte array.  For convenience, two seeds are also

// hashed into the result.

uint64 CityHash64WithSeeds(const char *buf, size_t len,

                           uint64 seed0, uint64 seed1);

// Hash function for a byte array.

uint128 CityHash128(const char *s, size_t len);

// Hash function for a byte array.  For convenience, a 128-bit seed is also

// hashed into the result.

uint128 CityHash128WithSeed(const char *s, size_t len, uint128 seed);

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

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

inline uint64 Hash128to64(const uint128& x) {

  // Murmur-inspired hashing.

  const uint64 kMul = 0x9ddfea08eb382d69;

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

  a ^= (a >> 47);

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

  b ^= (b >> 47);

  b *= kMul;

  return b;

}

#endif  // CITY_HASH_H_