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#pragma once
#include <condition_variable>
#include <mutex>
#include <optional>
#include <utility>
namespace cru::concurrent {
namespace details {
template <typename T>
struct ConcurrentQueueNode {
ConcurrentQueueNode(T&& value, ConcurrentQueueNode* next = nullptr)
: value(std::move(value)), next(next) {}
T value;
ConcurrentQueueNode* next;
};
} // namespace details
template <typename T>
class ConcurrentQueue {
public:
ConcurrentQueue() {}
ConcurrentQueue(const ConcurrentQueue&) = delete;
ConcurrentQueue& operator=(const ConcurrentQueue&) = delete;
~ConcurrentQueue() {
if (head_) {
auto node = head_;
while (node) {
auto next = node->next;
delete node;
node = next;
}
}
}
public:
void Push(T&& value) {
std::unique_lock<std::mutex> lock(mutex_);
if (head_ == nullptr) {
head_ = tail_ = new details::ConcurrentQueueNode<T>(std::move(value));
condition_variable_.notify_one();
} else {
tail_->next = new details::ConcurrentQueueNode<T>(std::move(value));
tail_ = tail_->next;
}
}
T Pull() {
std::unique_lock<std::mutex> lock(mutex_);
if (head_ == nullptr) {
condition_variable_.wait(lock);
}
assert(head_ != nullptr);
auto value = std::move(head_->value);
auto next = head_->next;
delete head_;
head_ = next;
if (next == nullptr) {
tail_ = nullptr;
}
return value;
}
std::optional<T> Poll() {
std::unique_lock<std::mutex> lock(mutex_);
if (head_ == nullptr) {
return std::nullopt;
}
auto value = std::move(head_->value);
auto next = head_->next;
delete head_;
head_ = next;
if (next == nullptr) {
tail_ = nullptr;
}
return value;
}
private:
details::ConcurrentQueueNode<T>* head_ = nullptr;
details::ConcurrentQueueNode<T>* tail_ = nullptr;
std::mutex mutex_;
std::condition_variable condition_variable_;
};
} // namespace cru::concurrent
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