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 //
 // Copyright (c) 2019 Vinnie Falco (vinnie.falco@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_IMPL_OBJECT_HPP
 #define BOOST_JSON_IMPL_OBJECT_HPP
 
 #include <boost/json/value.hpp>
 #include <iterator>
 #include <cmath>
 #include <type_traits>
 #include <utility>
 
 namespace boost {
 namespace json {
 
 namespace detail {
 
 // Objects with size less than or equal
 // to this number will use a linear search
 // instead of the more expensive hash function.
 static
 constexpr
 std::size_t
 small_object_size_ = 18;
 
 BOOST_STATIC_ASSERT(
     small_object_size_ <
     BOOST_JSON_MAX_STRUCTURED_SIZE);
 
 } // detail
 
 //----------------------------------------------------------
 
 struct alignas(key_value_pair)
     object::table
 {
     std::uint32_t size = 0;
     std::uint32_t capacity = 0;
     std::uintptr_t salt = 0;
 
 #if defined(_MSC_VER) && BOOST_JSON_ARCH == 32
     // VFALCO If we make key_value_pair smaller,
     //        then we might want to revisit this
     //        padding.
     BOOST_STATIC_ASSERT(
         sizeof(key_value_pair) == 32);
     char pad[4] = {}; // silence warnings
 #endif
 
     constexpr table();
 
     // returns true if we use a linear
     // search instead of the hash table.
     bool is_small() const noexcept
     {
         return capacity <=
             detail::small_object_size_;
     }
 
     key_value_pair&
     operator[](
         std::size_t pos) noexcept
     {
         return reinterpret_cast<
             key_value_pair*>(
                 this + 1)[pos];
     }
 
     // VFALCO This is exported for tests
     BOOST_JSON_DECL
     std::size_t
     digest(string_view key) const noexcept;
 
     inline
     index_t&
     bucket(std::size_t hash) noexcept;
 
     inline
     index_t&
     bucket(string_view key) noexcept;
 
     inline
     void
     clear() noexcept;
 
     static
     inline
     table*
     allocate(
         std::size_t capacity,
         std::uintptr_t salt,
         storage_ptr const& sp);
 
     static
     void
     deallocate(
         table* p,
         storage_ptr const& sp) noexcept
     {
         if(p->capacity == 0)
             return;
         if(! p->is_small())
             sp->deallocate(p,
                 sizeof(table) + p->capacity * (
                     sizeof(key_value_pair) +
                     sizeof(index_t)));
         else
             sp->deallocate(p,
                 sizeof(table) + p->capacity *
                     sizeof(key_value_pair));
     }
 };
 
 //----------------------------------------------------------
 
 class object::revert_construct
 {
     object* obj_;
 
     BOOST_JSON_DECL
     void
     destroy() noexcept;
 
 public:
     explicit
     revert_construct(
         object& obj) noexcept
         : obj_(&obj)
     {
     }
 
     ~revert_construct()
     {
         if(! obj_)
             return;
         destroy();
     }
 
     void
     commit() noexcept
     {
         obj_ = nullptr;
     }
 };
 
 //----------------------------------------------------------
 
 class object::revert_insert
 {
     object* obj_;
     table* t_ = nullptr;
     std::size_t size_;
 
     BOOST_JSON_DECL
     void
     destroy() noexcept;
 
 public:
     explicit
     revert_insert(
         object& obj,
         std::size_t capacity)
         : obj_(&obj)
         , size_(obj_->size())
     {
         if( capacity > obj_->capacity() )
             t_ = obj_->reserve_impl(capacity);
     }
 
     ~revert_insert()
     {
         if(! obj_)
             return;
 
         destroy();
         if( t_ )
         {
             table::deallocate( obj_->t_, obj_->sp_ );
             obj_->t_ = t_;
         }
         else
         {
             obj_->t_->size = static_cast<index_t>(size_);
         }
     }
 
     void
     commit() noexcept
     {
         BOOST_ASSERT(obj_);
         if( t_ )
             table::deallocate( t_, obj_->sp_ );
         obj_ = nullptr;
     }
 };
 
 //----------------------------------------------------------
 //
 // Iterators
 //
 //----------------------------------------------------------
 
 auto
 object::
 begin() noexcept ->
     iterator
 {
     return &(*t_)[0];
 }
 
 auto
 object::
 begin() const noexcept ->
     const_iterator
 {
     return &(*t_)[0];
 }
 
 auto
 object::
 cbegin() const noexcept ->
     const_iterator
 {
     return &(*t_)[0];
 }
 
 auto
 object::
 end() noexcept ->
     iterator
 {
     return &(*t_)[t_->size];
 }
 
 auto
 object::
 end() const noexcept ->
     const_iterator
 {
     return &(*t_)[t_->size];
 }
 
 auto
 object::
 cend() const noexcept ->
     const_iterator
 {
     return &(*t_)[t_->size];
 }
 
 auto
 object::
 rbegin() noexcept ->
     reverse_iterator
 {
     return reverse_iterator(end());
 }
 
 auto
 object::
 rbegin() const noexcept ->
     const_reverse_iterator
 {
     return const_reverse_iterator(end());
 }
 
 auto
 object::
 crbegin() const noexcept ->
     const_reverse_iterator
 {
     return const_reverse_iterator(end());
 }
 
 auto
 object::
 rend() noexcept ->
     reverse_iterator
 {
     return reverse_iterator(begin());
 }
 
 auto
 object::
 rend() const noexcept ->
     const_reverse_iterator
 {
     return const_reverse_iterator(begin());
 }
 
 auto
 object::
 crend() const noexcept ->
     const_reverse_iterator
 {
     return const_reverse_iterator(begin());
 }
 
 //----------------------------------------------------------
 //
 // Capacity
 //
 //----------------------------------------------------------
 
 bool
 object::
 empty() const noexcept
 {
     return t_->size == 0;
 }
 
 auto
 object::
 size() const noexcept ->
     std::size_t
 {
     return t_->size;
 }
 
 constexpr
 std::size_t
 object::
 max_size() noexcept
 {
     // max_size depends on the address model
     using min = std::integral_constant<std::size_t,
         (std::size_t(-1) - sizeof(table)) /
             (sizeof(key_value_pair) + sizeof(index_t))>;
     return min::value < BOOST_JSON_MAX_STRUCTURED_SIZE ?
         min::value : BOOST_JSON_MAX_STRUCTURED_SIZE;
 }
 
 auto
 object::
 capacity() const noexcept ->
     std::size_t
 {
     return t_->capacity;
 }
 
 void
 object::
 reserve(std::size_t new_capacity)
 {
     if( new_capacity <= capacity() )
         return;
     table* const old_table = reserve_impl(new_capacity);
     table::deallocate( old_table, sp_ );
 }
 
 //----------------------------------------------------------
 //
 // Lookup
 //
 //----------------------------------------------------------
 
 value&
 object::
 at(string_view key, source_location const& loc) &
 {
     auto const& self = *this;
     return const_cast< value& >( self.at(key, loc) );
 }
 
 value&&
 object::
 at(string_view key, source_location const& loc) &&
 {
     return std::move( at(key, loc) );
 }
 
 //----------------------------------------------------------
 
 template<class P, class>
 auto
 object::
 insert(P&& p) ->
     std::pair<iterator, bool>
 {
     key_value_pair v(
         std::forward<P>(p), sp_);
     return emplace_impl( v.key(), pilfer(v) );
 }
 
 template<class M>
 auto
 object::
 insert_or_assign(
     string_view key, M&& m) ->
         std::pair<iterator, bool>
 {
     std::pair<iterator, bool> result = emplace_impl(
         key, key, static_cast<M&&>(m) );
     if( !result.second )
     {
         value(static_cast<M>(m), sp_).swap(
             result.first->value());
     }
     return result;
 }
 
 template<class Arg>
 auto
 object::
 emplace(
     string_view key,
     Arg&& arg) ->
         std::pair<iterator, bool>
 {
     return emplace_impl( key, key, static_cast<Arg&&>(arg) );
 }
 
 //----------------------------------------------------------
 //
 // (private)
 //
 //----------------------------------------------------------
 
 template<class InputIt>
 void
 object::
 construct(
     InputIt first,
     InputIt last,
     std::size_t min_capacity,
     std::input_iterator_tag)
 {
     reserve(min_capacity);
     revert_construct r(*this);
     while(first != last)
     {
         insert(*first);
         ++first;
     }
     r.commit();
 }
 
 template<class InputIt>
 void
 object::
 construct(
     InputIt first,
     InputIt last,
     std::size_t min_capacity,
     std::forward_iterator_tag)
 {
     auto n = static_cast<
         std::size_t>(std::distance(
             first, last));
     if( n < min_capacity)
         n = min_capacity;
     reserve(n);
     revert_construct r(*this);
     while(first != last)
     {
         insert(*first);
         ++first;
     }
     r.commit();
 }
 
 template<class InputIt>
 void
 object::
 insert(
     InputIt first,
     InputIt last,
     std::input_iterator_tag)
 {
     // Since input iterators cannot be rewound,
     // we keep inserted elements on an exception.
     //
     while(first != last)
     {
         insert(*first);
         ++first;
     }
 }
 
 template<class InputIt>
 void
 object::
 insert(
     InputIt first,
     InputIt last,
     std::forward_iterator_tag)
 {
     auto const n =
         static_cast<std::size_t>(
             std::distance(first, last));
     auto const n0 = size();
     if(n > max_size() - n0)
     {
         BOOST_STATIC_CONSTEXPR source_location loc = BOOST_CURRENT_LOCATION;
         detail::throw_system_error( error::object_too_large, &loc );
     }
     revert_insert r( *this, n0 + n );
     while(first != last)
     {
         insert(*first);
         ++first;
     }
     r.commit();
 }
 
 template< class... Args >
 std::pair<object::iterator, bool>
 object::
 emplace_impl( string_view key, Args&& ... args )
 {
     std::pair<iterator, std::size_t> search_result(nullptr, 0);
     if( !empty() )
     {
         search_result = detail::find_in_object(*this, key);
         if( search_result.first )
             return { search_result.first, false };
     }
 
     // we create the new value before reserving, in case it is a reference to
     // a subobject of the current object
     key_value_pair kv( static_cast<Args&&>(args)..., sp_ );
     // the key might get deallocated too
     key = kv.key();
 
     std::size_t const old_capacity = capacity();
     reserve(size() + 1);
     if( (empty() && capacity() > detail::small_object_size_)
             || (capacity() != old_capacity) )
         search_result.second = detail::digest(
             key.begin(), key.end(), t_->salt);
 
     BOOST_ASSERT(
         t_->is_small() ||
         (search_result.second ==
             detail::digest(key.begin(), key.end(), t_->salt)) );
 
     return { insert_impl(pilfer(kv), search_result.second), true };
 }
 
 //----------------------------------------------------------
 
 namespace detail {
 
 unchecked_object::
 ~unchecked_object()
 {
     if(! data_)
         return;
     if(sp_.is_not_shared_and_deallocate_is_trivial())
         return;
     value* p = data_;
     while(size_--)
     {
         p[0].~value();
         p[1].~value();
         p += 2;
     }
 }
 
 } // detail
 
 } // namespace json
 } // namespace boost
 
 #endif

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