//
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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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#ifdef BOOST_JSON_STANDALONE
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# if __has_include(<memory_resource>)
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# include <memory_resource>
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# ifndef __cpp_lib_memory_resource
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# error Support for std::memory_resource is required to use Boost.JSON standalone
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# endif
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# elif __has_include(<experimental/memory_resource>)
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# include <experimental/memory_resource>
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# warning Support for std::memory_resource is required to use Boost.JSON standalone, using std::experimental::memory_resource as fallback
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# else
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# error Header <memory_resource> is required to use Boost.JSON standalone
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# endif
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#else
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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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#endif
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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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This type alias is set depending
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on how the library is configured:
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@par Use with Boost
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If the macro `BOOST_JSON_STANDALONE` is
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not defined, this type will be an alias
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for `boost::container::pmr::memory_resource`.
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Compiling a program using the library will
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require Boost, and a compiler conforming
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to C++11 or later.
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@par Use without Boost
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If the macro `BOOST_JSON_STANDALONE` is
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defined, this type will be an alias
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for `std::pmr::memory_resource`.
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Compiling a program using the library will
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require only a compiler conforming to C++17
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or later.
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@see https://en.cppreference.com/w/cpp/memory/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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This type alias is set depending
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on how the library is configured:
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@par Use with Boost
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If the macro `BOOST_JSON_STANDALONE` is
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not defined, this type will be an alias template
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for `boost::container::pmr::polymorphic_allocator`.
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Compiling a program using the library will
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require Boost, and a compiler conforming
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to C++11 or later.
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@par Use without Boost
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If the macro `BOOST_JSON_STANDALONE` is
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defined, this type will be an alias template
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for `std::pmr::polymorphic_allocator`.
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Compiling a program using the library will
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require only a compiler conforming to C++17
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or later.
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@see https://en.cppreference.com/w/cpp/memory/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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#elif defined(BOOST_JSON_STANDALONE)
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# if __has_include(<memory_resource>)
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using memory_resource = std::pmr::memory_resource;
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template<class T>
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using polymorphic_allocator =
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std::pmr::polymorphic_allocator<T>;
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# else
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using memory_resource = std::experimental::pmr::memory_resource;
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template<class T>
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using polymorphic_allocator =
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std::experimental::pmr::polymorphic_allocator<T>;
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# endif
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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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