blocking_queue.h

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
 
#pragma once
 
#include <glog/logging.h>
 
#include <condition_variable>
#include <queue>
 
#include "absl/status/statusor.h"
 
namespace resdb {
 
template <typename T>
class BlockingQueue {
 public:
  BlockingQueue() = default;
  BlockingQueue(const std::string& name) : name_(name) {}
  void Push(T&& data) {
    std::lock_guard<std::mutex> lk(mutex_);
    queue_.push(std::move(data));
    cv_.notify_all();
  }
 
  void Push(T& data) {
    std::lock_guard<std::mutex> lk(mutex_);
    queue_.push(std::move(data));
    cv_.notify_all();
  }
 
  absl::StatusOr<T*> Front() {
    std::unique_lock<std::mutex> lk(mutex_);
    if (queue_.empty()) {
      return nullptr;
    }
    return &queue_.front();
  }
 
  T Pop() {
    std::unique_lock<std::mutex> lk(mutex_);
    cv_.wait_for(lk, std::chrono::microseconds(timeout_ms_),
                 [&] { return !queue_.empty(); });
 
    if (queue_.empty()) {
      return nullptr;
    }
    auto resp = std::move(queue_.front());
    queue_.pop();
    return resp;
  }
 
  T Pop(int timeout_ms) {
    std::unique_lock<std::mutex> lk(mutex_);
    if (timeout_ms > 0) {
      cv_.wait_for(lk, std::chrono::microseconds(timeout_ms),
                   [&] { return !queue_.empty(); });
    }
    if (queue_.empty()) {
      return nullptr;
    }
    auto resp = std::move(queue_.front());
    queue_.pop();
    return resp;
  }
 
  T PopWithSize(int timeout_ms, size_t size) {
    std::unique_lock<std::mutex> lk(mutex_);
    if (timeout_ms > 0) {
      cv_.wait_for(lk, std::chrono::microseconds(timeout_ms),
                   [&] { return queue_.size() >= size; });
    }
    if (queue_.empty()) {
      return nullptr;
    }
    auto resp = std::move(queue_.front());
    queue_.pop();
    return resp;
  }
 
 private:
  std::string name_;
  std::condition_variable cv_;
  std::mutex mutex_;
  //  std::queue<T> queue_ GUARDED_BY(mutex_);
  std::queue<T> queue_;
  int64_t timeout_ms_ = 500;  // microsecond for timeout.
};
 
}  // namespace resdb