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111 lines
3.5 KiB
C++
111 lines
3.5 KiB
C++
/**************************************************************
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* @file queue_impl.hpp
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* @brief A queue implementation written in standard c++11
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* suitable for both low-end microcontrollers all the way
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* to HPC machines. Lock-free for single consumer single
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* producer scenarios.
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**************************************************************/
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/**************************************************************
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* Copyright (c) 2023 Djordje Nedic
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated
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* documentation files (the "Software"), to deal in the Software
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* without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to
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* whom the Software is furnished to do so, subject to the
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* following conditions:
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*
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* The above copyright notice and this permission notice shall
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* be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
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* KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
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* WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
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* PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
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* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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* This file is part of lockfree
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*
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* Author: Djordje Nedic <nedic.djordje2@gmail.com>
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* Version: v2.0.8
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**************************************************************/
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namespace lockfree {
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namespace spsc {
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/********************** PUBLIC METHODS ************************/
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template <typename T, size_t size> Queue<T, size>::Queue() : _r(0U), _w(0U) {}
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template <typename T, size_t size> bool Queue<T, size>::Push(const T &element) {
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/*
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The full check needs to be performed using the next write index not to
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miss the case when the read index wrapped and write index is at the end
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*/
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const size_t w = _w.load(std::memory_order_relaxed);
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size_t w_next = w + 1;
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if (w_next == size) {
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w_next = 0U;
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}
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/* Full check */
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const size_t r = _r.load(std::memory_order_acquire);
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if (w_next == r) {
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return false;
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}
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/* Place the element */
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_data[w] = element;
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/* Store the next write index */
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_w.store(w_next, std::memory_order_release);
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return true;
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}
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template <typename T, size_t size> bool Queue<T, size>::Pop(T &element) {
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/* Preload indexes with adequate memory ordering */
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size_t r = _r.load(std::memory_order_relaxed);
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const size_t w = _w.load(std::memory_order_acquire);
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/* Empty check */
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if (r == w) {
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return false;
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}
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/* Remove the element */
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element = _data[r];
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/* Increment the read index */
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r++;
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if (r == size) {
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r = 0U;
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}
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/* Store the read index */
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_r.store(r, std::memory_order_release);
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return true;
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}
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/********************* std::optional API **********************/
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#if __cplusplus >= 201703L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
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template <typename T, size_t size>
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std::optional<T> Queue<T, size>::PopOptional() {
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T element;
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bool result = Pop(element);
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if (result) {
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return element;
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} else {
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return {};
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}
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}
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#endif
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} /* namespace spsc */
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} /* namespace lockfree */
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