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//
// Copyright (c) 2023 Dmitry Arkhipov (grisumbras@yandex.ru)
//
// 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
//
// tag::example_use_allocator[]
/*
This example uses a context that stores an allocator to create sequences during conversions
*/
#include <boost/container/pmr/monotonic_buffer_resource.hpp>
#include <boost/container/pmr/vector.hpp>
#include <boost/json.hpp>
#include <boost/system/errc.hpp>
using namespace boost::json;
using namespace boost::container;
template< class Alloc >
struct use_allocator_t
{
Alloc allocator;
};
template< class Alloc >
use_allocator_t< Alloc >
use_allocator( Alloc alloc ) noexcept
{
return { alloc };
}
template<
class T,
class Alloc,
class FullContext,
class = typename std::enable_if<
is_sequence_like<T>::value &&
std::uses_allocator<T, Alloc>::value
>::type >
boost::system::result<T>
tag_invoke( try_value_to_tag<T>, const value& jv, const use_allocator_t<Alloc>& ctx, const FullContext& full_ctx )
{
array const* arr = jv.if_array();
if( !arr )
return {
boost::system::in_place_error,
make_error_code(boost::system::errc::invalid_argument) };
T result(ctx.allocator);
auto ins = std::inserter(result, result.end());
for( value const& val: *arr )
{
using ValueType = typename T::value_type;
auto elem_res = try_value_to<ValueType>( val, full_ctx );
if( elem_res.has_error() )
return {boost::system::in_place_error, elem_res.error()};
*ins++ = std::move(*elem_res);
}
return result;
}
int
main(int, char**)
{
value const jv = { 1, 2, 3, 4, 5, 6, 7, 8 };
unsigned char buf[1024];
pmr::monotonic_buffer_resource mr( buf, sizeof(buf) );
auto v = value_to< pmr::vector<int> >(
jv,
use_allocator( pmr::polymorphic_allocator<int>(&mr) ) );
assert( v.size() == jv.as_array().size() );
for( auto i = 0u; i < v.size(); ++i )
assert( v[i] == jv.at(i).to_number<int>() );
return EXIT_SUCCESS;
}
// end::example_use_allocator[]
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