120 lines
2.9 KiB
C++
120 lines
2.9 KiB
C++
// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
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// Distributed under the MIT License (http://opensource.org/licenses/MIT)
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// cirucal q view of std::vector.
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#pragma once
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#include <vector>
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namespace spdlog {
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namespace details {
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template<typename T>
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class circular_q
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{
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size_t max_items_ = 0;
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typename std::vector<T>::size_type head_ = 0;
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typename std::vector<T>::size_type tail_ = 0;
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size_t overrun_counter_ = 0;
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std::vector<T> v_;
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public:
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using value_type = T;
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// empty ctor - create a disabled queue with no elements allocated at all
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circular_q() = default;
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explicit circular_q(size_t max_items)
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: max_items_(max_items + 1) // one item is reserved as marker for full q
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, v_(max_items_)
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{}
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circular_q(const circular_q &) = default;
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circular_q &operator=(const circular_q &) = default;
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// move cannot be default,
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// since we need to reset head_, tail_, etc to zero in the moved object
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circular_q(circular_q &&other) SPDLOG_NOEXCEPT
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{
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copy_moveable(std::move(other));
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}
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circular_q &operator=(circular_q &&other) SPDLOG_NOEXCEPT
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{
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copy_moveable(std::move(other));
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return *this;
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}
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// push back, overrun (oldest) item if no room left
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void push_back(T &&item)
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{
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if (max_items_ > 0)
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{
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v_[tail_] = std::move(item);
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tail_ = (tail_ + 1) % max_items_;
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if (tail_ == head_) // overrun last item if full
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{
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head_ = (head_ + 1) % max_items_;
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++overrun_counter_;
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}
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}
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}
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// Return reference to the front item.
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// If there are no elements in the container, the behavior is undefined.
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const T &front() const
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{
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return v_[head_];
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}
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T &front()
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{
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return v_[head_];
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}
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// Pop item from front.
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// If there are no elements in the container, the behavior is undefined.
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void pop_front()
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{
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head_ = (head_ + 1) % max_items_;
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}
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bool empty() const
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{
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return tail_ == head_;
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}
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bool full() const
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{
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// head is ahead of the tail by 1
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if (max_items_ > 0)
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{
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return ((tail_ + 1) % max_items_) == head_;
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}
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return false;
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}
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size_t overrun_counter() const
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{
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return overrun_counter_;
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}
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private:
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// copy from other&& and reset it to disabled state
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void copy_moveable(circular_q &&other) SPDLOG_NOEXCEPT
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{
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max_items_ = other.max_items_;
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head_ = other.head_;
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tail_ = other.tail_;
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overrun_counter_ = other.overrun_counter_;
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v_ = std::move(other.v_);
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// put &&other in disabled, but valid state
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other.max_items_ = 0;
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other.head_ = other.tail_ = 0;
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other.overrun_counter_ = 0;
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}
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};
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} // namespace details
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} // namespace spdlog
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