rocksdb/util/channel.h

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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#pragma once
#include <condition_variable>
#include <mutex>
#include <queue>
#include <utility>
namespace ROCKSDB_NAMESPACE {
template <class T>
class channel {
public:
explicit channel() : eof_(false) {}
channel(const channel&) = delete;
void operator=(const channel&) = delete;
void sendEof() {
std::lock_guard<std::mutex> lk(lock_);
eof_ = true;
cv_.notify_all();
}
bool eof() {
std::lock_guard<std::mutex> lk(lock_);
return buffer_.empty() && eof_;
}
size_t size() const {
std::lock_guard<std::mutex> lk(lock_);
return buffer_.size();
}
// writes elem to the queue
void write(T&& elem) {
std::unique_lock<std::mutex> lk(lock_);
buffer_.emplace(std::forward<T>(elem));
cv_.notify_one();
}
/// Moves a dequeued element onto elem, blocking until an element
/// is available.
// returns false if EOF
bool read(T& elem) {
std::unique_lock<std::mutex> lk(lock_);
cv_.wait(lk, [&] { return eof_ || !buffer_.empty(); });
if (eof_ && buffer_.empty()) {
return false;
}
elem = std::move(buffer_.front());
buffer_.pop();
cv_.notify_one();
return true;
}
private:
std::condition_variable cv_;
mutable std::mutex lock_;
std::queue<T> buffer_;
bool eof_;
};
} // namespace ROCKSDB_NAMESPACE