87 lines
1.9 KiB
C++
87 lines
1.9 KiB
C++
//
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// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2020
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#pragma once
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#include <cstring>
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#include <type_traits>
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namespace td {
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namespace detail {
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template <class T>
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class As {
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public:
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explicit As(void *ptr) : ptr_(ptr) {
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}
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As(const As &new_value) = delete;
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As &operator=(const As &) = delete;
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As(As &&) = default;
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As &operator=(As &&new_value) && {
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std::memcpy(ptr_, new_value.ptr_, sizeof(T));
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return *this;
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}
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~As() = default;
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As &operator=(const T &new_value) && {
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std::memcpy(ptr_, &new_value, sizeof(T));
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return *this;
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}
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operator T() const {
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T res;
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std::memcpy(&res, ptr_, sizeof(T));
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return res;
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}
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bool operator==(const As &other) const {
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return this->operator T() == other.operator T();
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}
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private:
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void *ptr_;
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};
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template <class T>
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class ConstAs {
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public:
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explicit ConstAs(const void *ptr) : ptr_(ptr) {
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}
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operator T() const {
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T res;
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std::memcpy(&res, ptr_, sizeof(T));
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return res;
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}
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private:
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const void *ptr_;
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};
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} // namespace detail
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// no std::is_trivially_copyable in libstdc++ before 5.0
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#if __GLIBCXX__
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#define TD_IS_TRIVIALLY_COPYABLE(T) __has_trivial_copy(T)
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#else
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#define TD_IS_TRIVIALLY_COPYABLE(T) std::is_trivially_copyable<T>::value
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#endif
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template <class ToT, class FromT,
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std::enable_if_t<TD_IS_TRIVIALLY_COPYABLE(ToT) && TD_IS_TRIVIALLY_COPYABLE(FromT), int> = 0>
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detail::As<ToT> as(FromT *from) {
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return detail::As<ToT>(from);
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}
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template <class ToT, class FromT,
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std::enable_if_t<TD_IS_TRIVIALLY_COPYABLE(ToT) && TD_IS_TRIVIALLY_COPYABLE(FromT), int> = 0>
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const detail::ConstAs<ToT> as(const FromT *from) {
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return detail::ConstAs<ToT>(from);
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}
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} // namespace td
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