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- //
- // Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)
- // Copyright (c) 2020 Krystian Stasiowski (sdkrystian@gmail.com)
- // Copyright (c) 2022 Dmitry Arkhipov (grisumbras@gmail.com)
- //
- // 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)
- //
- // Official repository: https://github.com/boostorg/json
- //
- #ifndef BOOST_JSON_VALUE_FROM_HPP
- #define BOOST_JSON_VALUE_FROM_HPP
- #include <boost/json/detail/value_from.hpp>
- namespace boost {
- namespace json {
- /** Convert an object of type `T` to @ref value.
- This function attempts to convert an object
- of type `T` to @ref value using
- @li one of @ref value's constructors,
- @li a library-provided generic conversion, or
- @li a user-provided overload of `tag_invoke`.
- Out of the box the function supports types satisfying
- <a href="https://en.cppreference.com/w/cpp/named_req/SequenceContainer"><em>SequenceContainer</em></a>,
- arrays, arithmetic types, `bool`, `std::tuple`, `std::pair`,
- `std::variant`, `std::optional`, `std::monostate`, and `std::nullopt_t`.
- Conversion of other types is done by calling an overload of `tag_invoke`
- found by argument-dependent lookup. Its signature should be similar to:
- @code
- void tag_invoke( value_from_tag, value&, T );
- @endcode
- @par Exception Safety
- Strong guarantee.
- @tparam T The type of the object to convert.
- @param t The object to convert.
- @param jv @ref value out parameter.
- @see @ref value_from_tag, @ref value_to,
- <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1895r0.pdf">
- tag_invoke: A general pattern for supporting customisable functions</a>
- */
- template<class T>
- void
- value_from(
- T&& t,
- value& jv)
- {
- using bare_T = detail::remove_cvref<T>;
- BOOST_STATIC_ASSERT(detail::conversion_round_trips<
- bare_T, detail::value_from_conversion>::value);
- using impl = detail::value_from_implementation<bare_T>;
- detail::value_from_helper(jv, std::forward<T>(t), impl());
- }
- /** Convert an object of type `T` to @ref value.
- This function attempts to convert an object
- of type `T` to @ref value using
- @li one of @ref value's constructors,
- @li a library-provided generic conversion, or
- @li a user-provided overload of `tag_invoke`.
- Out of the box the function supports types satisfying
- <a href="https://en.cppreference.com/w/cpp/named_req/SequenceContainer"><em>SequenceContainer</em></a>,
- arrays, arithmetic types, `bool`, `std::tuple`, `std::pair`,
- `std::variant`, `std::optional`, `std::monostate`, and `std::nullopt_t`.
- Conversion of other types is done by calling an overload of `tag_invoke`
- found by argument-dependent lookup. Its signature should be similar to:
- @code
- void tag_invoke( value_from_tag, value&, T );
- @endcode
- A @ref value constructed
- with the @ref storage_ptr passed to @ref value_from is
- passed as the second argument to ensure that the memory
- resource is correctly propagated.
- @par Exception Safety
- Strong guarantee.
- @tparam T The type of the object to convert.
- @returns `t` converted to @ref value.
- @param t The object to convert.
- @param sp A storage pointer referring to the memory resource
- to use for the returned @ref value. The default argument for this
- parameter is `{}`.
- @see @ref value_from_tag, @ref value_to,
- <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1895r0.pdf">
- tag_invoke: A general pattern for supporting customisable functions</a>
- */
- template<class T>
- value
- value_from(
- T&& t,
- storage_ptr sp = {})
- {
- value jv(std::move(sp));
- json::value_from(
- std::forward<T>(t), jv);
- return jv;
- }
- /** Determine if `T` can be converted to @ref value.
- If `T` can be converted to @ref value via a
- call to @ref value_from, the static data member `value`
- is defined as `true`. Otherwise, `value` is
- defined as `false`.
- @see @ref value_from
- */
- #ifdef BOOST_JSON_DOCS
- template<class T>
- using has_value_from = __see_below__;
- #else
- template<class T>
- using has_value_from = detail::can_convert<
- detail::remove_cvref<T>, detail::value_from_conversion>;
- #endif
- } // namespace json
- } // namespace boost
- #endif
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