mpmc_blocking_q.h
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// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)
#pragma once
// multi producer-multi consumer blocking queue.
// enqueue(..) - will block until room found to put the new message.
// enqueue_nowait(..) - will return immediately with false if no room left in
// the queue.
// dequeue_for(..) - will block until the queue is not empty or timeout have
// passed.
#include <spdlog/details/circular_q.h>
#include <condition_variable>
#include <mutex>
namespace spdlog {
namespace details {
template<typename T>
class mpmc_blocking_queue
{
public:
using item_type = T;
explicit mpmc_blocking_queue(size_t max_items)
: q_(max_items)
{}
#ifndef __MINGW32__
// try to enqueue and block if no room left
void enqueue(T &&item)
{
{
std::unique_lock<std::mutex> lock(queue_mutex_);
pop_cv_.wait(lock, [this] { return !this->q_.full(); });
q_.push_back(std::move(item));
}
push_cv_.notify_one();
}
// enqueue immediately. overrun oldest message in the queue if no room left.
void enqueue_nowait(T &&item)
{
{
std::unique_lock<std::mutex> lock(queue_mutex_);
q_.push_back(std::move(item));
}
push_cv_.notify_one();
}
// try to dequeue item. if no item found. wait upto timeout and try again
// Return true, if succeeded dequeue item, false otherwise
bool dequeue_for(T &popped_item, std::chrono::milliseconds wait_duration)
{
{
std::unique_lock<std::mutex> lock(queue_mutex_);
if (!push_cv_.wait_for(lock, wait_duration, [this] { return !this->q_.empty(); }))
{
return false;
}
popped_item = std::move(q_.front());
q_.pop_front();
}
pop_cv_.notify_one();
return true;
}
#else
// apparently mingw deadlocks if the mutex is released before cv.notify_one(),
// so release the mutex at the very end each function.
// try to enqueue and block if no room left
void enqueue(T &&item)
{
std::unique_lock<std::mutex> lock(queue_mutex_);
pop_cv_.wait(lock, [this] { return !this->q_.full(); });
q_.push_back(std::move(item));
push_cv_.notify_one();
}
// enqueue immediately. overrun oldest message in the queue if no room left.
void enqueue_nowait(T &&item)
{
std::unique_lock<std::mutex> lock(queue_mutex_);
q_.push_back(std::move(item));
push_cv_.notify_one();
}
// try to dequeue item. if no item found. wait upto timeout and try again
// Return true, if succeeded dequeue item, false otherwise
bool dequeue_for(T &popped_item, std::chrono::milliseconds wait_duration)
{
std::unique_lock<std::mutex> lock(queue_mutex_);
if (!push_cv_.wait_for(lock, wait_duration, [this] { return !this->q_.empty(); }))
{
return false;
}
popped_item = std::move(q_.front());
q_.pop_front();
pop_cv_.notify_one();
return true;
}
#endif
size_t overrun_counter()
{
std::unique_lock<std::mutex> lock(queue_mutex_);
return q_.overrun_counter();
}
size_t size()
{
std::unique_lock<std::mutex> lock(queue_mutex_);
return q_.size();
}
private:
std::mutex queue_mutex_;
std::condition_variable push_cv_;
std::condition_variable pop_cv_;
spdlog::details::circular_q<T> q_;
};
} // namespace details
} // namespace spdlog