// // Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2020 // // Distributed under the Boost Software License, Version 1.0. (See accompanying // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) // #pragma once #include "td/utils/common.h" #if TD_HAVE_ABSL #include <absl/hash/hash.h> #endif #include <utility> namespace td { // A simple wrapper for absl::flat_hash_map, std::unordered_map and probably some our implementaion of hash map in // the future // We will introduce out own Hashing utility like an absl one. class Hasher { public: Hasher() = default; explicit Hasher(size_t init_value) : hash_(init_value) { } std::size_t finalize() const { return hash_; } static Hasher combine(Hasher hasher, size_t value) { hasher.hash_ ^= value; return hasher; } template <class A, class B> static Hasher combine(Hasher hasher, const std::pair<A, B> &value) { hasher = AbslHashValue(std::move(hasher), value.first); hasher = AbslHashValue(std::move(hasher), value.second); return hasher; } private: std::size_t hash_{0}; }; template <class IgnoreT> class TdHash { public: template <class T> std::size_t operator()(const T &value) const noexcept { return AbslHashValue(Hasher(), value).finalize(); } }; #if TD_HAVE_ABSL template <class T> using AbslHash = absl::Hash<T>; #endif // default hash implementations template <class H, class T> decltype(H::combine(std::declval<H>(), std::declval<T>())) AbslHashValue(H hasher, const T &value) { return H::combine(std::move(hasher), value); } #if TD_HAVE_ABSL template <class T> using Hash = AbslHash<T>; #else template <class T> using Hash = TdHash<T>; #endif } // namespace td