4e35befcf2
In some places we use the `*reinterpret_cast<const net::packed<T>*>(&x)` pattern to reinterpret memory. This is a violation of C++'s aliasing rules, which invokes undefined behaviour. The blessed way to correctly reinterpret memory is to copy it into a new object. Let's do that. Note: the reinterpret_cast way has no performance advantage. Compilers recognize the memory copy pattern and optimize it away.
53 lines
1.5 KiB
C++
53 lines
1.5 KiB
C++
/*
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* Copyright (C) 2021 ScyllaDB
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Scylla is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <cstring>
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#include <cstddef>
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#include <type_traits>
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template <class T> concept Trivial = std::is_trivial_v<T>;
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template <class T> concept TriviallyCopyable = std::is_trivially_copyable_v<T>;
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// C++20 has std::bit_cast, which does the same thing,
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// (but better, because it supports constexpr through compiler magic)
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// but it hasn't made its way to our libstdc++ yet.
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template <Trivial To, TriviallyCopyable From>
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requires (sizeof(To) == sizeof(From))
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To bit_cast(const From& src) noexcept {
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To dst;
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std::memcpy(&dst, &src, sizeof(To));
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return dst;
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}
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template <Trivial To>
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To read_unaligned(const void* src) {
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To dst;
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std::memcpy(&dst, src, sizeof(To));
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return dst;
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}
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template <TriviallyCopyable From>
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void write_unaligned(void* dst, const From& src) {
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std::memcpy(dst, &src, sizeof(From));
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}
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