forked from mirrors/gecko-dev
0e6bc87c63
A custom defintion wrapping fu2::function_base is used to customize the inline buffer's size and alignment to make it compatible with nsTArray. Without the custom wrapper, `alignof(max_align_t)` is used, which is larger than nsTArray's max alignment on some platforms. Differential Revision: https://phabricator.services.mozilla.com/D145691
47 lines
1.8 KiB
C++
47 lines
1.8 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_MoveOnlyFunction_h
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#define mozilla_MoveOnlyFunction_h
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// Use stl-like empty propagation to avoid issues with wrapping closures which
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// implicitly coerce to bool.
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#define FU2_WITH_LIMITED_EMPTY_PROPAGATION
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#include "function2/function2.hpp"
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namespace mozilla {
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/// A type like `std::function`, but with support for move-only callable
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/// objects.
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///
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/// A similar type is proposed to be added to the standard library as
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/// `std::move_only_function` in C++23.
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///
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/// Unlike `std::function`, the function signature may be given const or
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/// reference qualifiers which will be applied to `operator()`. This can be used
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/// to declare const qualified or move-only functions.
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///
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/// The implementation this definition depends on (function2) also has support
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/// for callables with overload sets, however support for this was not exposed
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/// to align better with the proposed `std::move_only_function`, which does not
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/// support overload sets.
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///
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/// A custom typedef over `fu2::function_base` is used to control the size and
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/// alignment of the inline storage to store 2 aligned pointers, and ensure the
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/// type is compatible with `nsTArray`.
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template <typename Signature>
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using MoveOnlyFunction = fu2::function_base<
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/* IsOwning */ true,
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/* IsCopyable */ false,
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/* Capacity */ fu2::capacity_fixed<2 * sizeof(void*), alignof(void*)>,
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/* IsThrowing */ false,
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/* HasStrongExceptionGuarantee */ false,
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/* Signature */ Signature>;
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} // namespace mozilla
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#endif // mozilla_MoveOnlyFunction_h
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