daw_json_default_constuctor.h

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// Copyright (c) Darrell Wright
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// Official repository: https://github.com/beached/daw_json_link
//
 
#pragma once
 
#include "daw/json/impl/version.h"
 
#include "daw/json/concepts/daw_nullable_value.h"
#include "daw/json/daw_json_default_constuctor_fwd.h"
#include "daw/json/impl/daw_json_assert.h"
 
#include <daw/daw_attributes.h>
#include <daw/daw_enable_requires.h>
#include <daw/daw_move.h>
#include <daw/daw_scope_guard.h>
 
#include <array>
#include <cstddef>
#include <iterator>
#include <type_traits>
#include <unordered_map>
#include <utility>
#include <vector>
 
namespace daw::json {
  inline namespace DAW_JSON_VER {
    namespace json_details {
      template<typename>
      inline constexpr bool is_std_allocator_v = false;
 
      template<typename T>
      inline constexpr bool is_std_allocator_v<std::allocator<T>> = true;
    } // namespace json_details
 
    template<typename T, std::size_t Sz>
    struct default_constructor<std::array<T, Sz>> {
      template<typename Iterator, std::size_t... Is>
      DAW_ATTRIB_INLINE static constexpr std::array<T, Sz>
      construct_array( Iterator first, Iterator last,
                       std::index_sequence<Is...> ) {
        auto const get_result = [&]( std::size_t ) {
          if( first != last ) {
            if constexpr( std::is_move_constructible_v<T> or
                          std::is_copy_constructible_v<T> ) {
              auto result = *first;
              ++first;
              return result;
            } else {
              // Only use for non-movable/copyable types
              auto const run_after_parse = on_exit_success( [&] {
                ++first;
              } );
              (void)run_after_parse;
              return *first;
            }
          }
          return T{ };
        };
        return std::array<T, Sz>{ get_result( Is )... };
      }
 
      DAW_JSON_CPP23_STATIC_CALL_OP_DISABLE_WARNING DAW_ATTRIB_INLINE
        DAW_JSON_CPP23_STATIC_CALL_OP constexpr std::array<T, Sz>
        operator( )( std::array<T, Sz> &&v )
          DAW_JSON_CPP23_STATIC_CALL_OP_CONST {
        return std::move( v );
      }
 
      template<typename Iterator, typename Last>
      DAW_ATTRIB_INLINE
        DAW_JSON_CPP23_STATIC_CALL_OP constexpr std::array<T, Sz>
        operator( )( Iterator first,
                     Last last ) DAW_JSON_CPP23_STATIC_CALL_OP_CONST {
        return construct_array( std::move( first ),
                                std::move( last ),
                                std::make_index_sequence<Sz>{ } );
      }
      DAW_JSON_CPP23_STATIC_CALL_OP_ENABLE_WARNING
    }; // namespace daw::json
 
#if defined( DAW_JSON_HAS_CPP23_RANGE_CTOR )
    namespace json_details {
      template<typename F, typename L>
      struct iter_range_t {
        F first;
        L last;
 
        explicit iter_range_t( ) = default;
        explicit constexpr iter_range_t( F f, L l ) noexcept
          : first( f )
          , last( l ) {}
 
        [[nodiscard]] constexpr F begin( ) const noexcept {
          return first;
        }
 
        [[nodiscard]] constexpr L end( ) const noexcept {
          return last;
        }
      };
      template<typename F, typename L>
      iter_range_t( F, L ) -> iter_range_t<F, L>;
    } // namespace json_details
 
    template<typename T, typename Alloc>
    struct default_constructor<std::vector<T, Alloc>> {
      DAW_JSON_CPP23_STATIC_CALL_OP_DISABLE_WARNING
      DAW_ATTRIB_INLINE
      DAW_JSON_CPP23_STATIC_CALL_OP DAW_JSON_CX_VECTOR std::vector<T, Alloc>
      operator( )( std::vector<T, Alloc> &&v )
        DAW_JSON_CPP23_STATIC_CALL_OP_CONST
        noexcept( noexcept( std::vector<T, Alloc>( v ) ) ) {
        return std::move( v );
      }
 
      template<typename Iterator, typename Last>
      DAW_ATTRIB_INLINE
        DAW_JSON_CPP23_STATIC_CALL_OP DAW_JSON_CX_VECTOR std::vector<T, Alloc>
        operator( )( Iterator first, Last last, Alloc const &alloc = Alloc{ } )
          DAW_JSON_CPP23_STATIC_CALL_OP_CONST {
        if constexpr( requires { last - first; } or
                      not json_details::is_std_allocator_v<Alloc> ) {
          return std::vector<T, Alloc>(
            std::from_range,
            json_details::iter_range_t{ std::move( first ), std::move( last ) },
            alloc );
        } else {
          using reserve_amount = daw::constant<
            ( 4096U / sizeof( T ) ) == 0 ? 1 : ( 4096U / sizeof( T ) )>;
          auto result = std::vector<T, Alloc>( alloc );
          // Lets use a WAG and go for a 4k page size
          result.reserve( reserve_amount::value );
          result.assign_range( json_details::iter_range_t{
            std::move( first ), std::move( last ) } );
          return result;
        }
      }
      DAW_JSON_CPP23_STATIC_CALL_OP_ENABLE_WARNING
    };
 
#else
    template<typename T, typename Alloc>
    struct default_constructor<std::vector<T, Alloc>> {
      DAW_JSON_CPP23_STATIC_CALL_OP_DISABLE_WARNING
      DAW_ATTRIB_INLINE
      DAW_JSON_CPP23_STATIC_CALL_OP DAW_JSON_CX_VECTOR std::vector<T, Alloc>
      operator( )( std::vector<T, Alloc> &&v )
        DAW_JSON_CPP23_STATIC_CALL_OP_CONST
        noexcept( noexcept( std::vector<T, Alloc>( v ) ) ) {
        return std::move( v );
      }
 
      template<typename Iterator, typename Last>
      DAW_ATTRIB_INLINE
        DAW_JSON_CPP23_STATIC_CALL_OP DAW_JSON_CX_VECTOR std::vector<T, Alloc>
        operator( )( Iterator first, Last last, Alloc const &alloc = Alloc{ } )
          DAW_JSON_CPP23_STATIC_CALL_OP_CONST {
        if constexpr( std::is_same_v<std::random_access_iterator_tag,
                                     typename std::iterator_traits<
                                       Iterator>::iterator_category> or
                      not json_details::is_std_allocator_v<Alloc> ) {
          return std::vector<T, Alloc>(
            std::move( first ), std::move( last ), alloc );
        } else {
          using reserve_amount = daw::constant<4096U / ( sizeof( T ) * 8U )>;
          auto result = std::vector<T, Alloc>( alloc );
          // Lets use a WAG and go for a 4k page size
          result.reserve( reserve_amount::value );
          result.assign( std::move( first ), std::move( last ) );
          return result;
        }
      }
      DAW_JSON_CPP23_STATIC_CALL_OP_ENABLE_WARNING
    };
#endif
 
    template<typename Key, typename T, typename Hash, typename CompareEqual,
             typename Alloc>
    struct default_constructor<
      std::unordered_map<Key, T, Hash, CompareEqual, Alloc>> {
 
      DAW_JSON_CPP23_STATIC_CALL_OP_DISABLE_WARNING
      DAW_ATTRIB_INLINE DAW_JSON_CPP23_STATIC_CALL_OP
        std::unordered_map<Key, T, Hash, CompareEqual, Alloc>
        operator( )( std::unordered_map<Key, T, Hash, CompareEqual, Alloc> &&v )
          DAW_JSON_CPP23_STATIC_CALL_OP_CONST noexcept( noexcept(
            std::unordered_map<Key, T, Hash, CompareEqual, Alloc>( v ) ) ) {
        return std::move( v );
      }
 
      static constexpr std::size_t count = 1;
      template<typename Iterator>
      DAW_ATTRIB_INLINE DAW_JSON_CPP23_STATIC_CALL_OP
        std::unordered_map<Key, T, Hash, CompareEqual, Alloc>
        operator( )( Iterator first, Iterator last,
                     Alloc const &alloc = Alloc{ } )
          DAW_JSON_CPP23_STATIC_CALL_OP_CONST {
        return std::unordered_map<Key, T, Hash, CompareEqual, Alloc>(
          first, last, count, Hash{ }, CompareEqual{ }, alloc );
      }
      DAW_JSON_CPP23_STATIC_CALL_OP_ENABLE_WARNING
    };
 
    template<typename T>
    DAW_REQUIRES( concepts::is_nullable_value_v<T> )
    struct nullable_constructor<
      T DAW_ENABLEIF_S( concepts::is_nullable_value_v<T> )> {
      using value_type = concepts::nullable_value_type_t<T>;
      using rtraits_t = concepts::nullable_value_traits<T>;
 
      DAW_JSON_CPP23_STATIC_CALL_OP_DISABLE_WARNING
      [[nodiscard]] DAW_ATTRIB_INLINE
        DAW_JSON_CPP23_STATIC_CALL_OP constexpr auto
        operator( )( concepts::construct_nullable_with_empty_t )
          DAW_JSON_CPP23_STATIC_CALL_OP_CONST
        noexcept( concepts::is_nullable_empty_nothrow_constructible_v<T> ) {
        static_assert( concepts::is_nullable_empty_constructible_v<T> );
        return rtraits_t{ }( concepts::construct_nullable_with_empty );
      }
 
      template<typename... Args DAW_ENABLEIF(
        concepts::is_nullable_value_constructible_v<T, Args...> )>
      DAW_REQUIRES( concepts::is_nullable_value_constructible_v<T, Args...> )
      [[nodiscard]] DAW_ATTRIB_INLINE DAW_JSON_CPP23_STATIC_CALL_OP
        constexpr auto
        operator( )( Args &&...args ) DAW_JSON_CPP23_STATIC_CALL_OP_CONST
        noexcept(
          concepts::is_nullable_value_nothrow_constructible_v<T, Args...> ) {
        return rtraits_t{ }( concepts::construct_nullable_with_value,
                             DAW_FWD( args )... );
      }
 
      template<typename Pointer DAW_ENABLEIF(
        concepts::is_nullable_pointer_constructible_v<T, Pointer *> )>
      DAW_REQUIRES(
        concepts::is_nullable_pointer_constructible_v<T, Pointer *> )
      [[nodiscard]] DAW_ATTRIB_INLINE DAW_JSON_CPP23_STATIC_CALL_OP
        constexpr auto
        operator( )( concepts::construct_nullable_with_pointer_t,
                     Pointer *ptr ) DAW_JSON_CPP23_STATIC_CALL_OP_CONST
        noexcept(
          concepts::is_nullable_value_nothrow_constructible_v<T, Pointer> ) {
        return rtraits_t{ }( concepts::construct_nullable_with_pointer, ptr );
      }
      DAW_JSON_CPP23_STATIC_CALL_OP_ENABLE_WARNING
    };
  } // namespace DAW_JSON_VER
} // namespace daw::json