ex/frame_allocator.hpp

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1		//
2		// Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
3		//
4		// Distributed under the Boost Software License, Version 1.0. (See accompanying
5		// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6		//
7		// Official repository: https://github.com/cppalliance/capy
8		//
9
10		#ifndef BOOST_CAPY_FRAME_ALLOCATOR_HPP
11		#define BOOST_CAPY_FRAME_ALLOCATOR_HPP
12
13		#include <boost/capy/detail/config.hpp>
14		#include <boost/capy/detail/frame_memory_resource.hpp>
15
16		#include <memory_resource>
17
18		/* Design rationale (pdimov):
19		This accessor is a thin wrapper over a thread-local pointer.
20		It returns exactly what was stored, including nullptr. No
21		dynamic initializer on the thread-local; a dynamic TLS
22		initializer moves you into a costlier implementation bucket
23		on some platforms - avoid it.
24
25		Null handling is the caller's responsibility (e.g. in
26		promise_type::operator new). The accessor must not substitute
27		a default, because there are multiple valid choices
28		(new_delete_resource, the default pmr resource, etc.). If
29		the allocator is not set, it reports "not set" and the
30		caller interprets that however it wants. */
31
32		namespace boost {
33		namespace capy {
34
35		/** Thread-local storage for the current frame allocator.
36
37		This function returns a reference to the thread-local pointer
38		that holds the current memory_resource for frame allocation.
39		The pointer is set by run_async before creating any tasks.
40
41		@return Reference to the thread-local memory_resource pointer.
42		*/
43		inline std::pmr::memory_resource*&
44	20615	current_frame_allocator() noexcept
45		{
46		static thread_local std::pmr::memory_resource* mr = nullptr;
47	20615	return mr;
48		}
49
50		// For backward compatibility
51		using detail::frame_memory_resource;
52
53		} // namespace capy
54		} // namespace boost
55
56		#endif
57