107 lines
2.7 KiB
C++
107 lines
2.7 KiB
C++
//
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// Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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// Official repository: https://github.com/boostorg/json
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//
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#ifndef BOOST_JSON_MEMORY_RESOURCE_HPP
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#define BOOST_JSON_MEMORY_RESOURCE_HPP
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#include <boost/json/detail/config.hpp>
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#include <boost/container/pmr/memory_resource.hpp>
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#include <boost/container/pmr/polymorphic_allocator.hpp>
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BOOST_JSON_NS_BEGIN
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#ifdef BOOST_JSON_DOCS
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/** The type of memory resource used by the library.
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Alias for `boost::container::pmr::memory_resource`.
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*/
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class memory_resource
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{
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};
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/** The type of polymorphic allocator used by the library.
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Alias template for `boost::container::pmr::polymorphic_allocator`.
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*/
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template<class T>
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class polymorphic_allocator;
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// VFALCO Bug: doc toolchain won't make this a ref
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//using memory_resource = __see_below__;
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#else
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using memory_resource = boost::container::pmr::memory_resource;
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template<class T>
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using polymorphic_allocator =
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boost::container::pmr::polymorphic_allocator<T>;
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#endif
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/** Return true if a memory resource's deallocate function has no effect.
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This metafunction may be specialized to indicate to
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the library that calls to the `deallocate` function of
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a @ref memory_resource have no effect. The implementation
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will elide such calls when it is safe to do so. By default,
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the implementation assumes that all memory resources
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require a call to `deallocate` for each memory region
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obtained by calling `allocate`.
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@par Example
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This example specializes the metafuction for `my_resource`,
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to indicate that calls to deallocate have no effect:
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@code
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// Forward-declaration for a user-defined memory resource
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struct my_resource;
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// It is necessary to specialize the template from
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// inside the namespace in which it is declared:
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namespace boost {
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namespace json {
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template<>
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struct is_deallocate_trivial< my_resource >
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{
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static constexpr bool value = true;
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};
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} // namespace json
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} // namespace boost
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@endcode
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It is usually not necessary for users to check this trait.
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Instead, they can call @ref storage_ptr::is_deallocate_trivial
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to determine if the pointed-to memory resource has a trivial
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deallocate function.
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@see
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@ref memory_resource,
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@ref storage_ptr
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*/
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template<class T>
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struct is_deallocate_trivial
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{
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/** A bool equal to true if calls to `T::do_deallocate` have no effect.
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The primary template sets `value` to false.
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*/
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static constexpr bool value = false;
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};
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BOOST_JSON_NS_END
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#endif
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