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tdlib-fork/tdutils/td/utils/as.h

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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019
//
// 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 <cstring>
#include <type_traits>
namespace td {
namespace detail {
template <class T>
class As {
public:
explicit As(void *ptr) : ptr_(ptr) {
}
As(const As &new_value) = delete;
As &operator=(const As &) = delete;
As(As &&) = default;
As &operator=(As &&new_value) && {
std::memcpy(ptr_, new_value.ptr_, sizeof(T));
return *this;
}
~As() = default;
As &operator=(const T &new_value) && {
std::memcpy(ptr_, &new_value, sizeof(T));
return *this;
}
operator T() const {
T res;
std::memcpy(&res, ptr_, sizeof(T));
return res;
}
bool operator==(const As &other) const {
return this->operator T() == other.operator T();
}
private:
void *ptr_;
};
template <class T>
class ConstAs {
public:
explicit ConstAs(const void *ptr) : ptr_(ptr) {
}
operator T() const {
T res;
std::memcpy(&res, ptr_, sizeof(T));
return res;
}
private:
const void *ptr_;
};
} // namespace detail
template <class ToT, class FromT,
std::enable_if_t<std::is_trivially_copyable<ToT>::value && std::is_trivially_copyable<FromT>::value, int> = 0>
detail::As<ToT> as(FromT *from) {
return detail::As<ToT>(from);
}
template <class ToT, class FromT,
std::enable_if_t<std::is_trivially_copyable<ToT>::value && std::is_trivially_copyable<FromT>::value, int> = 0>
const detail::ConstAs<ToT> as(const FromT *from) {
return detail::ConstAs<ToT>(from);
}
} // namespace td