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optional_reference_spec.hpp
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// Copyright (C) 2015-2018 Andrzej Krzemienski. // // Use, modification, and distribution is subject to 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) // // See http://www.boost.org/libs/optional for documentation. // // You are welcome to contact the author at: // akrzemi1@gmail.com #ifndef BOOST_OPTIONAL_DETAIL_OPTIONAL_REFERENCE_SPEC_AJK_03OCT2015_HPP #define BOOST_OPTIONAL_DETAIL_OPTIONAL_REFERENCE_SPEC_AJK_03OCT2015_HPP #ifdef BOOST_OPTIONAL_CONFIG_NO_PROPER_ASSIGN_FROM_CONST_INT #include <boost/type_traits/is_integral.hpp> #include <boost/type_traits/is_const.hpp> #endif # if 1 namespace boost { namespace detail { #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES template <class From> void prevent_binding_rvalue() { #ifndef BOOST_OPTIONAL_CONFIG_ALLOW_BINDING_TO_RVALUES BOOST_STATIC_ASSERT_MSG(boost::is_lvalue_reference<From>::value, "binding rvalue references to optional lvalue references is disallowed"); #endif } template <class T> BOOST_DEDUCED_TYPENAME boost::remove_reference<T>::type& forward_reference(T&& r) { BOOST_STATIC_ASSERT_MSG(boost::is_lvalue_reference<T>::value, "binding rvalue references to optional lvalue references is disallowed"); return boost::forward<T>(r); } #endif // BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES template <class T> struct is_const_integral { static const bool value = boost::is_const<T>::value && boost::is_integral<T>::value; }; template <class T> struct is_const_integral_bad_for_conversion { #if (!defined BOOST_OPTIONAL_CONFIG_ALLOW_BINDING_TO_RVALUES) && (defined BOOST_OPTIONAL_CONFIG_NO_PROPER_CONVERT_FROM_CONST_INT) static const bool value = boost::is_const<T>::value && boost::is_integral<T>::value; #else static const bool value = false; #endif }; template <class From> void prevent_assignment_from_false_const_integral() { #ifndef BOOST_OPTIONAL_CONFIG_ALLOW_BINDING_TO_RVALUES #ifdef BOOST_OPTIONAL_CONFIG_NO_PROPER_ASSIGN_FROM_CONST_INT // MSVC compiler without rvalue refernces: we need to disable the asignment from // const integral lvalue reference, as it may be an invalid temporary BOOST_STATIC_ASSERT_MSG(!is_const_integral<From>::value, "binding const lvalue references to integral types is disabled in this compiler"); #endif #endif } template <class T> struct is_optional_ { static const bool value = false; }; template <class U> struct is_optional_< ::boost::optional<U> > { static const bool value = true; }; template <class T> struct is_no_optional { static const bool value = !is_optional_<BOOST_DEDUCED_TYPENAME boost::decay<T>::type>::value; }; template <class T, class U> struct is_same_decayed { static const bool value = ::boost::is_same<T, BOOST_DEDUCED_TYPENAME ::boost::remove_reference<U>::type>::value || ::boost::is_same<T, const BOOST_DEDUCED_TYPENAME ::boost::remove_reference<U>::type>::value; }; template <class T, class U> struct no_unboxing_cond { static const bool value = is_no_optional<U>::value && !is_same_decayed<T, U>::value; }; } // namespace detail template <class T> class optional<T&> : public optional_detail::optional_tag { T* ptr_; public: typedef T& value_type; typedef T& reference_type; typedef T& reference_const_type; typedef T& rval_reference_type; typedef T* pointer_type; typedef T* pointer_const_type; optional() BOOST_NOEXCEPT : ptr_() {} optional(none_t) BOOST_NOEXCEPT : ptr_() {} template <class U> explicit optional(const optional<U&>& rhs) BOOST_NOEXCEPT : ptr_(rhs.get_ptr()) {} optional(const optional& rhs) BOOST_NOEXCEPT : ptr_(rhs.get_ptr()) {} // the following two implement a 'conditionally explicit' constructor: condition is a hack for buggy compilers with srewed conversion construction from const int template <class U> explicit optional(U& rhs, BOOST_DEDUCED_TYPENAME boost::enable_if_c<detail::is_same_decayed<T, U>::value && detail::is_const_integral_bad_for_conversion<U>::value, bool>::type = true) BOOST_NOEXCEPT : ptr_(boost::addressof(rhs)) {} template <class U> optional(U& rhs, BOOST_DEDUCED_TYPENAME boost::enable_if_c<detail::is_same_decayed<T, U>::value && !detail::is_const_integral_bad_for_conversion<U>::value, bool>::type = true) BOOST_NOEXCEPT : ptr_(boost::addressof(rhs)) {} optional& operator=(const optional& rhs) BOOST_NOEXCEPT { ptr_ = rhs.get_ptr(); return *this; } template <class U> optional& operator=(const optional<U&>& rhs) BOOST_NOEXCEPT { ptr_ = rhs.get_ptr(); return *this; } optional& operator=(none_t) BOOST_NOEXCEPT { ptr_ = 0; return *this; } void swap(optional& rhs) BOOST_NOEXCEPT { std::swap(ptr_, rhs.ptr_); } T& get() const { BOOST_ASSERT(ptr_); return *ptr_; } T* get_ptr() const BOOST_NOEXCEPT { return ptr_; } T* operator->() const { BOOST_ASSERT(ptr_); return ptr_; } T& operator*() const { BOOST_ASSERT(ptr_); return *ptr_; } T& value() const { return ptr_ ? *ptr_ : (throw_exception(bad_optional_access()), *ptr_); } bool operator!() const BOOST_NOEXCEPT { return ptr_ == 0; } BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT() void reset() BOOST_NOEXCEPT { ptr_ = 0; } bool is_initialized() const BOOST_NOEXCEPT { return ptr_ != 0; } bool has_value() const BOOST_NOEXCEPT { return ptr_ != 0; } template <typename F> optional<typename boost::result_of<F(T&)>::type> map(F f) const { if (this->has_value()) return f(this->get()); else return none; } template <typename F> optional<typename optional_detail::optional_value_type<typename boost::result_of<F(T&)>::type>::type> flat_map(F f) const { if (this->has_value()) return f(get()); else return none; } #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES optional(T&& /* rhs */) BOOST_NOEXCEPT { detail::prevent_binding_rvalue<T&&>(); } template <class R> optional(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::no_unboxing_cond<T, R>, bool>::type = true) BOOST_NOEXCEPT : ptr_(boost::addressof(r)) { detail::prevent_binding_rvalue<R>(); } template <class R> optional(bool cond, R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R>, bool>::type = true) BOOST_NOEXCEPT : ptr_(cond ? boost::addressof(r) : 0) { detail::prevent_binding_rvalue<R>(); } template <class R> BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R>, optional<T&>&>::type operator=(R&& r) BOOST_NOEXCEPT { detail::prevent_binding_rvalue<R>(); ptr_ = boost::addressof(r); return *this; } template <class R> void emplace(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R>, bool>::type = true) BOOST_NOEXCEPT { detail::prevent_binding_rvalue<R>(); ptr_ = boost::addressof(r); } template <class R> T& get_value_or(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R>, bool>::type = true) const BOOST_NOEXCEPT { detail::prevent_binding_rvalue<R>(); return ptr_ ? *ptr_ : r; } template <class R> T& value_or(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R>, bool>::type = true) const BOOST_NOEXCEPT { detail::prevent_binding_rvalue<R>(); return ptr_ ? *ptr_ : r; } template <class R> void reset(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R>, bool>::type = true) BOOST_NOEXCEPT { detail::prevent_binding_rvalue<R>(); ptr_ = boost::addressof(r); } template <class F> T& value_or_eval(F f) const { return ptr_ ? *ptr_ : detail::forward_reference(f()); } #else // BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES // the following two implement a 'conditionally explicit' constructor template <class U> explicit optional(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if_c<detail::no_unboxing_cond<T, U>::value && detail::is_const_integral_bad_for_conversion<U>::value, bool>::type = true) BOOST_NOEXCEPT : ptr_(boost::addressof(v)) { } template <class U> optional(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if_c<detail::no_unboxing_cond<T, U>::value && !detail::is_const_integral_bad_for_conversion<U>::value, bool>::type = true) BOOST_NOEXCEPT : ptr_(boost::addressof(v)) { } template <class U> optional(bool cond, U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U>, bool>::type = true) BOOST_NOEXCEPT : ptr_(cond ? boost::addressof(v) : 0) {} template <class U> BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U>, optional<T&>&>::type operator=(U& v) BOOST_NOEXCEPT { detail::prevent_assignment_from_false_const_integral<U>(); ptr_ = boost::addressof(v); return *this; } template <class U> void emplace(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U>, bool>::type = true) BOOST_NOEXCEPT { ptr_ = boost::addressof(v); } template <class U> T& get_value_or(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U>, bool>::type = true) const BOOST_NOEXCEPT { return ptr_ ? *ptr_ : v; } template <class U> T& value_or(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U>, bool>::type = true) const BOOST_NOEXCEPT { return ptr_ ? *ptr_ : v; } template <class U> void reset(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U>, bool>::type = true) BOOST_NOEXCEPT { ptr_ = boost::addressof(v); } template <class F> T& value_or_eval(F f) const { return ptr_ ? *ptr_ : f(); } #endif // BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES }; template <class T> void swap ( optional<T&>& x, optional<T&>& y) BOOST_NOEXCEPT { x.swap(y); } } // namespace boost #endif // 1/0 #endif // header guard