From 9971cd1d55b0481a2af74a7694b6dcf686176c7c Mon Sep 17 00:00:00 2001 From: Morph <39850852+Morph1984@users.noreply.github.com> Date: Sat, 25 Mar 2023 22:43:55 -0400 Subject: common: Port boost's hash_value implementation Ports a small subset of boost's hash_value implementation (<= 1.80.0). --- src/common/container_hash.h | 91 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 91 insertions(+) create mode 100644 src/common/container_hash.h (limited to 'src/common/container_hash.h') diff --git a/src/common/container_hash.h b/src/common/container_hash.h new file mode 100644 index 000000000..cfc5dfea8 --- /dev/null +++ b/src/common/container_hash.h @@ -0,0 +1,91 @@ +// SPDX-FileCopyrightText: 2005-2014 Daniel James +// SPDX-FileCopyrightText: 2016 Austin Appleby +// SPDX-License-Identifier: BSL-1.0 + +#include +#include +#include +#include +#include + +namespace Common { + +namespace detail { + +template + requires std::is_unsigned_v +inline std::size_t HashValue(T val) { + const unsigned int size_t_bits = std::numeric_limits::digits; + const unsigned int length = + (std::numeric_limits::digits - 1) / static_cast(size_t_bits); + + std::size_t seed = 0; + + for (unsigned int i = length * size_t_bits; i > 0; i -= size_t_bits) { + seed ^= static_cast(val >> i) + (seed << 6) + (seed >> 2); + } + + seed ^= static_cast(val) + (seed << 6) + (seed >> 2); + + return seed; +} + +template +struct HashCombineImpl { + template + static inline T fn(T seed, T value) { + seed ^= value + 0x9e3779b9 + (seed << 6) + (seed >> 2); + return seed; + } +}; + +template <> +struct HashCombineImpl<64> { + static inline std::uint64_t fn(std::uint64_t h, std::uint64_t k) { + const std::uint64_t m = (std::uint64_t(0xc6a4a793) << 32) + 0x5bd1e995; + const int r = 47; + + k *= m; + k ^= k >> r; + k *= m; + + h ^= k; + h *= m; + + // Completely arbitrary number, to prevent 0's + // from hashing to 0. + h += 0xe6546b64; + + return h; + } +}; + +} // namespace detail + +template +inline void HashCombine(std::size_t& seed, const T& v) { + seed = detail::HashCombineImpl::fn(seed, detail::HashValue(v)); +} + +template +inline std::size_t HashRange(It first, It last) { + std::size_t seed = 0; + + for (; first != last; ++first) { + HashCombine::value_type>(seed, *first); + } + + return seed; +} + +template +std::size_t HashValue(const std::array& v) { + return HashRange(v.cbegin(), v.cend()); +} + +template +std::size_t HashValue(const std::vector& v) { + return HashRange(v.cbegin(), v.cend()); +} + +} // namespace Common -- cgit v1.2.3