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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2026
//
// 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/config.h"
#include "td/utils/port/EventFd.h"
#if !TD_EVENTFD_UNSUPPORTED
#include "td/utils/port/Mutex.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);
}
for (int i = 0; i < 2; i++) {
auto guard = lock_.lock();
if (writer_vector_.empty()) {
if (i == 1) {
reader_vector_.clear();
reader_pos_ = 0;
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());
}
event_fd_.acquire();
}
UNREACHABLE();
}
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;
guard.reset();
event_fd_.release();
}
}
EventFd &reader_get_event_fd() {
return event_fd_;
}
void writer_flush() {
//nop
}
bool is_empty() {
auto guard = lock_.lock();
return writer_vector_.empty() && reader_vector_.empty();
}
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:
Mutex 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
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