153 lines
3.0 KiB
C++
153 lines
3.0 KiB
C++
//
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// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019
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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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#pragma once
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#include "td/utils/common.h"
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#include "td/utils/misc.h"
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#include "td/utils/port/EventFd.h"
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#if !TD_EVENTFD_UNSUPPORTED
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#include "td/utils/SpinLock.h"
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#include <utility>
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namespace td {
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// interface like in PollableQueue
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template <class T>
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class MpscPollableQueue {
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public:
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using ValueType = T;
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int reader_wait_nonblock() {
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auto ready = reader_vector_.size() - reader_pos_;
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if (ready != 0) {
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return narrow_cast<int>(ready);
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}
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for (int i = 0; i < 2; i++) {
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auto guard = lock_.lock();
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if (writer_vector_.empty()) {
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if (i == 1) {
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wait_event_fd_ = true;
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return 0;
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}
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} else {
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reader_vector_.clear();
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reader_pos_ = 0;
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std::swap(writer_vector_, reader_vector_);
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return narrow_cast<int>(reader_vector_.size());
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}
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event_fd_.acquire();
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}
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UNREACHABLE();
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}
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ValueType reader_get_unsafe() {
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return std::move(reader_vector_[reader_pos_++]);
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}
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void reader_flush() {
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//nop
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}
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void writer_put(ValueType value) {
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auto guard = lock_.lock();
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writer_vector_.push_back(std::move(value));
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if (wait_event_fd_) {
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wait_event_fd_ = false;
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guard.reset();
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event_fd_.release();
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}
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}
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EventFd &reader_get_event_fd() {
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return event_fd_;
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}
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void writer_flush() {
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//nop
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}
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void init() {
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event_fd_.init();
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}
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void destroy() {
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if (!event_fd_.empty()) {
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event_fd_.close();
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wait_event_fd_ = false;
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writer_vector_.clear();
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reader_vector_.clear();
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reader_pos_ = 0;
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}
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}
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// Just an example of usage
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int reader_wait() {
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int res;
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while ((res = reader_wait_nonblock()) == 0) {
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reader_get_event_fd().wait(1000);
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}
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return res;
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}
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private:
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SpinLock lock_;
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bool wait_event_fd_{false};
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EventFd event_fd_;
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std::vector<ValueType> writer_vector_;
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std::vector<ValueType> reader_vector_;
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size_t reader_pos_{0};
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};
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} // namespace td
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#else
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namespace td {
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// dummy implementation which shouldn't be used
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template <class T>
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class MpscPollableQueue {
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public:
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using ValueType = T;
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void init() {
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UNREACHABLE();
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}
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template <class PutValueType>
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void writer_put(PutValueType &&value) {
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UNREACHABLE();
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}
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void writer_flush() {
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UNREACHABLE();
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}
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int reader_wait_nonblock() {
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UNREACHABLE();
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return 0;
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}
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ValueType reader_get_unsafe() {
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UNREACHABLE();
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return ValueType();
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}
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void reader_flush() {
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UNREACHABLE();
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}
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MpscPollableQueue() = default;
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MpscPollableQueue(const MpscPollableQueue &) = delete;
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MpscPollableQueue &operator=(const MpscPollableQueue &) = delete;
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MpscPollableQueue(MpscPollableQueue &&) = delete;
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MpscPollableQueue &operator=(MpscPollableQueue &&) = delete;
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~MpscPollableQueue() = default;
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};
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} // namespace td
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#endif
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