// // Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019 // // Distributed under the Boost Software License, Version 1.0. (See accompanying // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) // #pragma once #include "td/utils/common.h" #include "td/utils/misc.h" #include "td/utils/port/EventFd.h" #if !TD_EVENTFD_UNSUPPORTED #include "td/utils/SpinLock.h" #include <utility> namespace td { // interface like in PollableQueue template <class T> class MpscPollableQueue { public: using ValueType = T; int reader_wait_nonblock() { auto ready = reader_vector_.size() - reader_pos_; if (ready != 0) { return narrow_cast<int>(ready); } auto guard = lock_.lock(); if (writer_vector_.empty()) { event_fd_.acquire(); wait_event_fd_ = true; return 0; } else { reader_vector_.clear(); reader_pos_ = 0; std::swap(writer_vector_, reader_vector_); return narrow_cast<int>(reader_vector_.size()); } } ValueType reader_get_unsafe() { return std::move(reader_vector_[reader_pos_++]); } void reader_flush() { //nop } void writer_put(ValueType value) { auto guard = lock_.lock(); writer_vector_.push_back(std::move(value)); if (wait_event_fd_) { wait_event_fd_ = false; event_fd_.release(); } } EventFd &reader_get_event_fd() { return event_fd_; } void writer_flush() { //nop } void init() { event_fd_.init(); } void destroy() { if (!event_fd_.empty()) { event_fd_.close(); wait_event_fd_ = false; writer_vector_.clear(); reader_vector_.clear(); reader_pos_ = 0; } } // Just an example of usage int reader_wait() { int res; while ((res = reader_wait_nonblock()) == 0) { reader_get_event_fd().wait(1000); } return res; } private: SpinLock lock_; bool wait_event_fd_{false}; EventFd event_fd_; std::vector<ValueType> writer_vector_; std::vector<ValueType> reader_vector_; size_t reader_pos_{0}; }; } // namespace td #else namespace td { // dummy implementation which shouldn't be used template <class T> class MpscPollableQueue { public: using ValueType = T; void init() { UNREACHABLE(); } template <class PutValueType> void writer_put(PutValueType &&value) { UNREACHABLE(); } void writer_flush() { UNREACHABLE(); } int reader_wait_nonblock() { UNREACHABLE(); return 0; } ValueType reader_get_unsafe() { UNREACHABLE(); return ValueType(); } void reader_flush() { UNREACHABLE(); } MpscPollableQueue() = default; MpscPollableQueue(const MpscPollableQueue &) = delete; MpscPollableQueue &operator=(const MpscPollableQueue &) = delete; MpscPollableQueue(MpscPollableQueue &&) = delete; MpscPollableQueue &operator=(MpscPollableQueue &&) = delete; ~MpscPollableQueue() = default; }; } // namespace td #endif