Boost C++ Libraries

boost/pfr/io.hpp

// Copyright (c) 2016-2024 Antony Polukhin
//
// 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)

#ifndef BOOST_PFR_IO_HPP
#define BOOST_PFR_IO_HPP
#pragma once

#include <boost/pfr/detail/config.hpp>

#include <boost/pfr/detail/detectors.hpp>
#include <boost/pfr/io_fields.hpp>

/// \file boost/pfr/io.hpp
/// Contains IO stream manipulator \forcedlink{io} for types.
/// If type is streamable using its own operator or its conversion operator, then the types operator is used.
///
/// \b Example:
/// \code
///     #include <boost/pfr/io.hpp>
///     struct comparable_struct {      // No operators defined for that structure
///         int i; short s; char data[7]; bool bl; int a,b,c,d,e,f;
///     };
///     // ...
///
///     comparable_struct s1 {0, 1, "Hello", false, 6,7,8,9,10,11};
///     std::cout << boost::pfr::io(s1);  // Outputs: {0, 1, H, e, l, l, o, , , 0, 6, 7, 8, 9, 10, 11}
/// \endcode
///
/// \podops for other ways to define operators and more details.
///
/// \b Synopsis:
namespace boost { namespace pfr {

namespace detail {

///////////////////// Helper typedefs
    template <class Stream, class Type>
    using enable_not_ostreamable_t = std::enable_if_t<
        not_appliable<ostreamable_detector, Stream&, const std::remove_reference_t<Type>&>::value,
        Stream&
    >;

    template <class Stream, class Type>
    using enable_not_istreamable_t = std::enable_if_t<
        not_appliable<istreamable_detector, Stream&, Type&>::value,
        Stream&
    >;

    template <class Stream, class Type>
    using enable_ostreamable_t = std::enable_if_t<
        !not_appliable<ostreamable_detector, Stream&, const std::remove_reference_t<Type>&>::value,
        Stream&
    >;

    template <class Stream, class Type>
    using enable_istreamable_t = std::enable_if_t<
        !not_appliable<istreamable_detector, Stream&, Type&>::value,
        Stream&
    >;

///////////////////// IO impl

template <class T>
struct io_impl {
    T value;
};

template <class Char, class Traits, class T>
enable_not_ostreamable_t<std::basic_ostream<Char, Traits>, T> operator<<(std::basic_ostream<Char, Traits>& out, io_impl<T>&& x) {
    return out << boost::pfr::io_fields(std::forward<T>(x.value));
}

template <class Char, class Traits, class T>
enable_ostreamable_t<std::basic_ostream<Char, Traits>, T> operator<<(std::basic_ostream<Char, Traits>& out, io_impl<T>&& x) {
    return out << x.value;
}

template <class Char, class Traits, class T>
enable_not_istreamable_t<std::basic_istream<Char, Traits>, T> operator>>(std::basic_istream<Char, Traits>& in, io_impl<T>&& x) {
    return in >> boost::pfr::io_fields(std::forward<T>(x.value));
}

template <class Char, class Traits, class T>
enable_istreamable_t<std::basic_istream<Char, Traits>, T> operator>>(std::basic_istream<Char, Traits>& in, io_impl<T>&& x) {
    return in >> x.value;
}

} // namespace detail

/// IO manipulator to read/write \aggregate `value` using its IO stream operators or using \forcedlink{io_fields} if operators are not available.
///
/// \b Example:
/// \code
///     struct my_struct { int i; short s; };
///     my_struct x;
///     std::stringstream ss;
///     ss << "{ 12, 13 }";
///     ss >> boost::pfr::io(x);
///     assert(x.i == 12);
///     assert(x.s == 13);
/// \endcode
///
/// \customio
template <class T>
auto io(T&& value) noexcept {
    return detail::io_impl<T>{std::forward<T>(value)};
}

}} // namespace boost::pfr

#endif // BOOST_PFR_IO_HPP