169 lines
4.4 KiB
C++
169 lines
4.4 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* Licensed under the Apache License Version 2.0 with LLVM Exceptions
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* https://llvm.org/LICENSE.txt
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <unifex/config.hpp>
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#include <unifex/get_stop_token.hpp>
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#include <unifex/receiver_concepts.hpp>
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#include <unifex/stop_token_concepts.hpp>
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#include <cstddef>
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#include <type_traits>
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#include <utility>
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#include <unifex/detail/prologue.hpp>
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namespace unifex {
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namespace _trampoline {
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class scheduler {
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std::size_t maxRecursionDepth_;
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public:
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scheduler() noexcept : maxRecursionDepth_(16) {}
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explicit scheduler(std::size_t depth) noexcept
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: maxRecursionDepth_(depth) {}
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private:
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struct operation_base {
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using execute_fn = void(operation_base*) noexcept;
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explicit operation_base(execute_fn* execute, std::size_t maxDepth) noexcept
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: execute_(execute)
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, maxRecursionDepth_(maxDepth)
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{}
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void execute() noexcept {
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execute_(this);
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}
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void start() noexcept {
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auto* currentState = trampoline_state::current_;
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if (currentState == nullptr) {
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trampoline_state state;
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execute();
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state.drain();
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} else if (currentState->recursionDepth_ < maxRecursionDepth_) {
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++currentState->recursionDepth_;
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execute();
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} else {
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// Exceeded recursion limit.
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next_ = std::exchange(
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currentState->head_,
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static_cast<operation_base*>(this));
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}
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}
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operation_base* next_ = nullptr;
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execute_fn* execute_;
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std::size_t maxRecursionDepth_;
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};
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struct trampoline_state {
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static thread_local trampoline_state* current_;
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trampoline_state() noexcept {
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current_ = this;
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}
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~trampoline_state() {
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current_ = nullptr;
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}
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void drain() noexcept;
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std::size_t recursionDepth_ = 1;
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operation_base* head_ = nullptr;
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};
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class schedule_sender;
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template <typename Receiver>
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struct _op {
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class type final : operation_base {
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UNIFEX_NO_UNIQUE_ADDRESS Receiver receiver_;
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friend schedule_sender;
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template <typename Receiver2>
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explicit type(Receiver2&& receiver, std::size_t maxDepth)
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: operation_base(&type::execute_impl, maxDepth)
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, receiver_((Receiver2 &&) receiver) {}
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static void execute_impl(operation_base* p) noexcept {
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auto& self = *static_cast<type*>(p);
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if (is_stop_never_possible_v<stop_token_type_t<Receiver&>>) {
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unifex::set_value(static_cast<Receiver&&>(self.receiver_));
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} else {
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if (get_stop_token(self.receiver_).stop_requested()) {
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unifex::set_done(static_cast<Receiver&&>(self.receiver_));
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} else {
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unifex::set_value(static_cast<Receiver&&>(self.receiver_));
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}
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}
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}
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public:
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using operation_base::start;
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};
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};
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template <typename Receiver>
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using operation = typename _op<remove_cvref_t<Receiver>>::type;
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class schedule_sender {
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public:
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explicit schedule_sender(std::size_t maxDepth) noexcept
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: maxRecursionDepth_(maxDepth)
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{}
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template <
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template <typename...> class Variant,
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template <typename...> class Tuple>
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using value_types = Variant<Tuple<>>;
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template <template <typename...> class Variant>
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using error_types = Variant<>;
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static constexpr bool sends_done = true;
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template <typename Receiver>
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operation<Receiver> connect(Receiver&& receiver) const& {
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return operation<Receiver>{(Receiver &&) receiver, maxRecursionDepth_};
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}
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private:
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std::size_t maxRecursionDepth_;
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};
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public:
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schedule_sender schedule() const noexcept {
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return schedule_sender{maxRecursionDepth_};
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}
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friend bool operator==(scheduler, scheduler) noexcept {
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return true;
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}
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friend bool operator!=(scheduler, scheduler) noexcept {
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return false;
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}
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};
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} // namespace _trampoline
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using trampoline_scheduler = _trampoline::scheduler;
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} // namespace unifex
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#include <unifex/detail/epilogue.hpp>
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