368 lines
12 KiB
C++
368 lines
12 KiB
C++
// See http://www.boost.org/libs/any for Documentation.
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#ifndef BOOST_ANY_INCLUDED
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#define BOOST_ANY_INCLUDED
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#include <boost/config.hpp>
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#ifdef BOOST_HAS_PRAGMA_ONCE
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# pragma once
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#endif
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/// \file boost/any.hpp
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/// \brief \copybrief boost::any
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// what: variant type boost::any
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// who: contributed by Kevlin Henney,
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// with features contributed and bugs found by
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// Antony Polukhin, Ed Brey, Mark Rodgers,
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// Peter Dimov, and James Curran
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// when: July 2001, April 2013 - 2020
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#include <boost/any/bad_any_cast.hpp>
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#include <boost/any/fwd.hpp>
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#include <boost/any/detail/placeholder.hpp>
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#include <boost/throw_exception.hpp>
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#include <boost/type_index.hpp>
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#include <memory> // for std::addressof
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#include <type_traits>
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namespace boost
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{
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/// \brief A class whose instances can hold instances of any
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/// type that satisfies \forcedlink{ValueType} requirements.
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class any
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{
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public:
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/// \post this->empty() is true.
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constexpr any() noexcept
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: content(0)
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{
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}
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/// Makes a copy of `value`, so
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/// that the initial content of the new instance is equivalent
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/// in both type and value to `value`.
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///
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/// \throws std::bad_alloc or any exceptions arising from the copy
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/// constructor of the contained type.
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template<typename ValueType>
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any(const ValueType & value)
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: content(new holder<
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typename std::remove_cv<typename std::decay<const ValueType>::type>::type
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>(value))
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{
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static_assert(
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!anys::detail::is_basic_any<ValueType>::value,
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"boost::any shall not be constructed from boost::anys::basic_any"
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);
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}
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/// Copy constructor that copies content of
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/// `other` into new instance, so that any content
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/// is equivalent in both type and value to the content of
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/// `other`, or empty if `other` is empty.
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///
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/// \throws May fail with a `std::bad_alloc`
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/// exception or any exceptions arising from the copy
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/// constructor of the contained type.
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any(const any & other)
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: content(other.content ? other.content->clone() : 0)
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{
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}
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/// Move constructor that moves content of
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/// `other` into new instance and leaves `other` empty.
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///
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/// \post other->empty() is true
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/// \throws Nothing.
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any(any&& other) noexcept
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: content(other.content)
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{
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other.content = 0;
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}
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/// Forwards `value`, so
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/// that the initial content of the new instance is equivalent
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/// in both type and value to `value` before the forward.
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///
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/// \throws std::bad_alloc or any exceptions arising from the move or
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/// copy constructor of the contained type.
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template<typename ValueType>
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any(ValueType&& value
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, typename std::enable_if<!std::is_same<any&, ValueType>::value >::type* = 0 // disable if value has type `any&`
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, typename std::enable_if<!std::is_const<ValueType>::value >::type* = 0) // disable if value has type `const ValueType&&`
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: content(new holder< typename std::decay<ValueType>::type >(std::forward<ValueType>(value)))
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{
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static_assert(
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!anys::detail::is_basic_any<typename std::decay<ValueType>::type>::value,
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"boost::any shall not be constructed from boost::anys::basic_any"
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);
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}
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/// Releases any and all resources used in management of instance.
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///
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/// \throws Nothing.
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~any() noexcept
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{
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delete content;
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}
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public: // modifiers
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/// Exchange of the contents of `*this` and `rhs`.
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///
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/// \returns `*this`
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/// \throws Nothing.
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any & swap(any & rhs) noexcept
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{
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placeholder* tmp = content;
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content = rhs.content;
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rhs.content = tmp;
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return *this;
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}
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/// Copies content of `rhs` into
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/// current instance, discarding previous content, so that the
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/// new content is equivalent in both type and value to the
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/// content of `rhs`, or empty if `rhs.empty()`.
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///
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/// \throws std::bad_alloc
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/// or any exceptions arising from the copy constructor of the
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/// contained type. Assignment satisfies the strong guarantee
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/// of exception safety.
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any & operator=(const any& rhs)
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{
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any(rhs).swap(*this);
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return *this;
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}
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/// Moves content of `rhs` into
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/// current instance, discarding previous content, so that the
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/// new content is equivalent in both type and value to the
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/// content of `rhs` before move, or empty if
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/// `rhs.empty()`.
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///
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/// \post `rhs->empty()` is true
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/// \throws Nothing.
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any & operator=(any&& rhs) noexcept
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{
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rhs.swap(*this);
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any().swap(rhs);
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return *this;
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}
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/// Forwards `rhs`,
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/// discarding previous content, so that the new content of is
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/// equivalent in both type and value to
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/// `rhs` before forward.
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///
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/// \throws std::bad_alloc
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/// or any exceptions arising from the move or copy constructor of the
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/// contained type. Assignment satisfies the strong guarantee
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/// of exception safety.
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template <class ValueType>
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any & operator=(ValueType&& rhs)
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{
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static_assert(
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!anys::detail::is_basic_any<typename std::decay<ValueType>::type>::value,
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"boost::anys::basic_any shall not be assigned into boost::any"
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);
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any(std::forward<ValueType>(rhs)).swap(*this);
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return *this;
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}
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public: // queries
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/// \returns `true` if instance is empty, otherwise `false`.
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/// \throws Nothing.
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bool empty() const noexcept
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{
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return !content;
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}
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/// \post this->empty() is true
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void clear() noexcept
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{
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any().swap(*this);
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}
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/// \returns the `typeid` of the
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/// contained value if instance is non-empty, otherwise
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/// `typeid(void)`.
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///
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/// Useful for querying against types known either at compile time or
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/// only at runtime.
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const boost::typeindex::type_info& type() const noexcept
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{
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return content ? content->type() : boost::typeindex::type_id<void>().type_info();
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}
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private: // types
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/// @cond
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class BOOST_SYMBOL_VISIBLE placeholder: public boost::anys::detail::placeholder
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{
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public:
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virtual placeholder * clone() const = 0;
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};
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template<typename ValueType>
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class holder final
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: public placeholder
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{
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public: // structors
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holder(const ValueType & value)
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: held(value)
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{
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}
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holder(ValueType&& value)
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: held(static_cast< ValueType&& >(value))
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{
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}
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public: // queries
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const boost::typeindex::type_info& type() const noexcept override
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{
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return boost::typeindex::type_id<ValueType>().type_info();
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}
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placeholder * clone() const BOOST_OVERRIDE
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{
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return new holder(held);
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}
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public: // representation
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ValueType held;
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private: // intentionally left unimplemented
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holder & operator=(const holder &);
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};
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private: // representation
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template<typename ValueType>
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friend ValueType * unsafe_any_cast(any *) noexcept;
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friend class boost::anys::unique_any;
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placeholder * content;
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/// @endcond
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};
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/// Exchange of the contents of `lhs` and `rhs`.
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/// \throws Nothing.
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inline void swap(any & lhs, any & rhs) noexcept
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{
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lhs.swap(rhs);
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}
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/// @cond
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// Note: The "unsafe" versions of any_cast are not part of the
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// public interface and may be removed at any time. They are
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// required where we know what type is stored in the any and can't
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// use typeid() comparison, e.g., when our types may travel across
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// different shared libraries.
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template<typename ValueType>
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inline ValueType * unsafe_any_cast(any * operand) noexcept
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{
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return std::addressof(
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static_cast<any::holder<ValueType> *>(operand->content)->held
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);
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}
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template<typename ValueType>
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inline const ValueType * unsafe_any_cast(const any * operand) noexcept
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{
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return boost::unsafe_any_cast<ValueType>(const_cast<any *>(operand));
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}
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/// @endcond
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/// \returns Pointer to a ValueType stored in `operand`, nullptr if
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/// `operand` does not contain specified `ValueType`.
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template<typename ValueType>
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ValueType * any_cast(any * operand) noexcept
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{
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return operand && operand->type() == boost::typeindex::type_id<ValueType>()
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? boost::unsafe_any_cast<typename std::remove_cv<ValueType>::type>(operand)
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: 0;
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}
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/// \returns Const pointer to a ValueType stored in `operand`, nullptr if
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/// `operand` does not contain specified `ValueType`.
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template<typename ValueType>
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inline const ValueType * any_cast(const any * operand) noexcept
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{
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return boost::any_cast<ValueType>(const_cast<any *>(operand));
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}
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/// \returns ValueType stored in `operand`
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/// \throws boost::bad_any_cast if `operand` does not contain
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/// specified ValueType.
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template<typename ValueType>
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ValueType any_cast(any & operand)
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{
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typedef typename std::remove_reference<ValueType>::type nonref;
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nonref * result = boost::any_cast<nonref>(std::addressof(operand));
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if(!result)
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boost::throw_exception(bad_any_cast());
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// Attempt to avoid construction of a temporary object in cases when
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// `ValueType` is not a reference. Example:
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// `static_cast<std::string>(*result);`
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// which is equal to `std::string(*result);`
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typedef typename std::conditional<
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std::is_reference<ValueType>::value,
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ValueType,
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typename std::add_lvalue_reference<ValueType>::type
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>::type ref_type;
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#ifdef BOOST_MSVC
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# pragma warning(push)
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# pragma warning(disable: 4172) // "returning address of local variable or temporary" but *result is not local!
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#endif
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return static_cast<ref_type>(*result);
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#ifdef BOOST_MSVC
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# pragma warning(pop)
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#endif
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}
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/// \returns `ValueType` stored in `operand`
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/// \throws boost::bad_any_cast if `operand` does not contain
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/// specified `ValueType`.
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template<typename ValueType>
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inline ValueType any_cast(const any & operand)
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{
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typedef typename std::remove_reference<ValueType>::type nonref;
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return boost::any_cast<const nonref &>(const_cast<any &>(operand));
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}
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/// \returns `ValueType` stored in `operand`, leaving the `operand` empty.
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/// \throws boost::bad_any_cast if `operand` does not contain
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/// specified `ValueType`.
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template<typename ValueType>
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inline ValueType any_cast(any&& operand)
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{
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static_assert(
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std::is_rvalue_reference<ValueType&&>::value /*true if ValueType is rvalue or just a value*/
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|| std::is_const< typename std::remove_reference<ValueType>::type >::value,
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"boost::any_cast shall not be used for getting nonconst references to temporary objects"
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);
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return boost::any_cast<ValueType>(operand);
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}
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}
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// Copyright Kevlin Henney, 2000, 2001, 2002. All rights reserved.
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// Copyright Antony Polukhin, 2013-2024.
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#endif
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