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common/cityhash: Use common types

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Allow sharing return types with the rest of the code base. For example,
we use 'u128 = std::array<u64, 2>', meanwhile Google's code uses
'uint128 = std::pair<u64, u64>'.

While we are at it, use size_t instead of std::size_t.
This commit is contained in:
ReinUsesLisp 2021-02-18 00:23:53 -03:00
parent 9ca5e52f07
commit f3805376f7
3 changed files with 100 additions and 116 deletions
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34
src/common/cityhash.h
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@ -61,50 +61,38 @@
#pragma once
#include <cstddef>
#include <cstdint>
#include <utility>
#include "common/common_types.h"
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);
[[nodiscard]] u64 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.
[[nodiscard]] uint64_t CityHash64WithSeed(const char* buf, std::size_t len, uint64_t seed);
[[nodiscard]] u64 CityHash64WithSeed(const char* buf, size_t len, u64 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);
[[nodiscard]] u64 CityHash64WithSeeds(const char* buf, size_t len, u64 seed0, u64 seed1);
// Hash function for a byte array.
[[nodiscard]] uint128 CityHash128(const char* s, std::size_t len);
[[nodiscard]] u128 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.
[[nodiscard]] uint128 CityHash128WithSeed(const char* s, std::size_t len, uint128 seed);
[[nodiscard]] u128 CityHash128WithSeed(const char* s, size_t len, u128 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) {
[[nodiscard]] inline u64 Hash128to64(const u128& x) {
// Murmur-inspired hashing.
const uint64_t kMul = 0x9ddfea08eb382d69ULL;
uint64_t a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul;
const u64 mul = 0x9ddfea08eb382d69ULL;
u64 a = (x[0] ^ x[1]) * mul;
a ^= (a >> 47);
uint64_t b = (Uint128High64(x) ^ a) * kMul;
u64 b = (x[1] ^ a) * mul;
b ^= (b >> 47);
b *= kMul;
b *= mul;
return b;
}