mirror of
https://github.com/citra-emu/citra.git
synced 2024-11-22 17:00:05 +00:00
112 lines
4.8 KiB
C++
112 lines
4.8 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
|
|
//
|
|
// http://code.google.com/p/cityhash/
|
|
//
|
|
// This file provides a few functions for hashing strings. All of them are
|
|
// high-quality functions in the sense that they pass standard tests such
|
|
// as Austin Appleby's SMHasher. They are also fast.
|
|
//
|
|
// For 64-bit x86 code, on short strings, we don't know of anything faster than
|
|
// CityHash64 that is of comparable quality. We believe our nearest competitor
|
|
// is Murmur3. For 64-bit x86 code, CityHash64 is an excellent choice for hash
|
|
// tables and most other hashing (excluding cryptography).
|
|
//
|
|
// For 64-bit x86 code, on long strings, the picture is more complicated.
|
|
// On many recent Intel CPUs, such as Nehalem, Westmere, Sandy Bridge, etc.,
|
|
// CityHashCrc128 appears to be faster than all competitors of comparable
|
|
// quality. CityHash128 is also good but not quite as fast. We believe our
|
|
// nearest competitor is Bob Jenkins' Spooky. We don't have great data for
|
|
// other 64-bit CPUs, but for long strings we know that Spooky is slightly
|
|
// faster than CityHash on some relatively recent AMD x86-64 CPUs, for example.
|
|
// Note that CityHashCrc128 is declared in citycrc.h.
|
|
//
|
|
// For 32-bit x86 code, we don't know of anything faster than CityHash32 that
|
|
// is of comparable quality. We believe our nearest competitor is Murmur3A.
|
|
// (On 64-bit CPUs, it is typically faster to use the other CityHash variants.)
|
|
//
|
|
// Functions in the CityHash family are not suitable for cryptography.
|
|
//
|
|
// Please see CityHash's README file for more details on our performance
|
|
// measurements and so on.
|
|
//
|
|
// WARNING: This code has been only lightly 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.
|
|
// It should work on all 32-bit and 64-bit platforms that allow unaligned reads;
|
|
// bug reports are welcome.
|
|
//
|
|
// 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.
|
|
|
|
#pragma once
|
|
|
|
#include <cstddef>
|
|
#include <cstdint>
|
|
#include <utility>
|
|
|
|
namespace Common {
|
|
|
|
using uint128 = std::pair<uint64_t, uint64_t>;
|
|
|
|
[[nodiscard]] inline uint64_t Uint128Low64(const uint128& x) {
|
|
return x.first;
|
|
}
|
|
[[nodiscard]] inline uint64_t Uint128High64(const uint128& x) {
|
|
return x.second;
|
|
}
|
|
|
|
// Hash function for a byte array.
|
|
[[nodiscard]] uint64_t CityHash64(const char* buf, std::size_t len);
|
|
|
|
// Hash function for a byte array. For convenience, a 64-bit seed is also
|
|
// hashed into the result.
|
|
[[nodiscard]] uint64_t CityHash64WithSeed(const char* buf, std::size_t len, uint64_t seed);
|
|
|
|
// Hash function for a byte array. For convenience, two seeds are also
|
|
// hashed into the result.
|
|
[[nodiscard]] uint64_t CityHash64WithSeeds(const char* buf, std::size_t len, uint64_t seed0,
|
|
uint64_t seed1);
|
|
|
|
// Hash function for a byte array.
|
|
[[nodiscard]] uint128 CityHash128(const char* s, std::size_t len);
|
|
|
|
// Hash function for a byte array. For convenience, a 128-bit seed is also
|
|
// hashed into the result.
|
|
[[nodiscard]] uint128 CityHash128WithSeed(const char* s, std::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.
|
|
[[nodiscard]] inline uint64_t Hash128to64(const uint128& x) {
|
|
// Murmur-inspired hashing.
|
|
const uint64_t kMul = 0x9ddfea08eb382d69ULL;
|
|
uint64_t a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul;
|
|
a ^= (a >> 47);
|
|
uint64_t b = (Uint128High64(x) ^ a) * kMul;
|
|
b ^= (b >> 47);
|
|
b *= kMul;
|
|
return b;
|
|
}
|
|
|
|
} // namespace Common
|