mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-22 15:42:02 +00:00
118 lines
4.6 KiB
C++
118 lines
4.6 KiB
C++
// 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, 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>
|
|
#include <utility>
|
|
|
|
/** This is a version of CityHash that predates v1.0.3 algorithm change.
|
|
* Why we need exactly this version?
|
|
* Although hash values of CityHash are not recommended for storing persistently anywhere,
|
|
* it has already been used this way in ClickHouse:
|
|
* - for calculation of checksums of compressed chunks and for data parts;
|
|
* - this version of CityHash is exposed in cityHash64 function in ClickHouse SQL language;
|
|
* - and already used by many users for data ordering, sampling and sharding.
|
|
*/
|
|
namespace CityHash_v1_0_2
|
|
{
|
|
|
|
typedef uint8_t uint8;
|
|
typedef uint32_t uint32;
|
|
typedef uint64_t uint64;
|
|
|
|
/// Represent an unsigned integer of 128 bits as it's used in CityHash.
|
|
/// Originally CityHash used `std::pair<uint64, uint64>` instead of this struct,
|
|
/// however the members `first` and `second` could be easily confused so they were renamed to `low64` and `high64`:
|
|
/// `first` -> `low64`, `second` -> `high64`.
|
|
struct uint128
|
|
{
|
|
uint64 low64 = 0;
|
|
uint64 high64 = 0;
|
|
|
|
uint128() = default;
|
|
uint128(uint64 low64_, uint64 high64_) : low64(low64_), high64(high64_) {}
|
|
|
|
friend auto operator<=>(const uint128 &, const uint128 &) = default;
|
|
};
|
|
|
|
inline uint64 Uint128Low64(const uint128 & x) { return x.low64; }
|
|
inline uint64 Uint128High64(const uint128 & x) { return x.high64; }
|
|
|
|
// 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 = 0x9ddfea08eb382d69ULL;
|
|
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_
|