mirror of
https://github.com/NixOS/nix
synced 2024-10-18 00:16:11 -04:00
d0e9878389
Splitting it out immediately answers questions like [this], without increasing the number of compilation units. I did consider using boost::hash_combine instead, but it doesn't seem to be quite as capable, accepting only two arguments. [this]: https://github.com/NixOS/nix/pull/11113#discussion_r1679991573
25 lines
595 B
C++
25 lines
595 B
C++
#pragma once
|
|
|
|
//!@file Hashing utilities for use with unordered_map, etc. (ie low level implementation logic, not domain logic like
|
|
//! Nix hashing)
|
|
|
|
#include <functional>
|
|
|
|
namespace nix {
|
|
|
|
/**
|
|
* hash_combine() from Boost. Hash several hashable values together
|
|
* into a single hash.
|
|
*/
|
|
inline void hash_combine(std::size_t & seed) {}
|
|
|
|
template<typename T, typename... Rest>
|
|
inline void hash_combine(std::size_t & seed, const T & v, Rest... rest)
|
|
{
|
|
std::hash<T> hasher;
|
|
seed ^= hasher(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
|
|
hash_combine(seed, rest...);
|
|
}
|
|
|
|
} // namespace nix
|