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173 lines
5.4 KiB
C++
173 lines
5.4 KiB
C++
/*
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A modified version of Bounded MPMC queue by Dmitry Vyukov.
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Original code from:
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http://www.1024cores.net/home/lock-free-algorithms/queues/bounded-mpmc-queue
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licensed by Dmitry Vyukov under the terms below:
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Simplified BSD license
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Copyright (c) 2010-2011 Dmitry Vyukov. All rights reserved.
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Redistribution and use in source and binary forms, with or without modification,
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are permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice, this list of
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conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice, this list
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of conditions and the following disclaimer in the documentation and/or other materials
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provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY DMITRY VYUKOV "AS IS" AND ANY EXPRESS OR IMPLIED
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WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
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SHALL DMITRY VYUKOV OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
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OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
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OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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The views and conclusions contained in the software and documentation are those of the authors and
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should not be interpreted as representing official policies, either expressed or implied, of Dmitry Vyukov.
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*/
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/*
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The code in its current form adds the license below:
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Copyright(c) 2015 Gabi Melman.
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Distributed under the MIT License (http://opensource.org/licenses/MIT)
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*/
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#pragma once
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#include <spdlog/common.h>
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#include <atomic>
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#include <utility>
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namespace spdlog
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{
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namespace details
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{
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template<typename T>
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class mpmc_bounded_queue
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{
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public:
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using item_type = T;
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mpmc_bounded_queue(size_t buffer_size)
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:max_size_(buffer_size),
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buffer_(new cell_t [buffer_size]),
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buffer_mask_(buffer_size - 1)
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{
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//queue size must be power of two
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if(!((buffer_size >= 2) && ((buffer_size & (buffer_size - 1)) == 0)))
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throw spdlog_ex("async logger queue size must be power of two");
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for (size_t i = 0; i != buffer_size; i += 1)
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buffer_[i].sequence_.store(i, std::memory_order_relaxed);
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enqueue_pos_.store(0, std::memory_order_relaxed);
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dequeue_pos_.store(0, std::memory_order_relaxed);
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}
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~mpmc_bounded_queue()
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{
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delete [] buffer_;
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}
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bool enqueue(T&& data)
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{
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cell_t* cell;
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size_t pos = enqueue_pos_.load(std::memory_order_relaxed);
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for (;;)
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{
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cell = &buffer_[pos & buffer_mask_];
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size_t seq = cell->sequence_.load(std::memory_order_acquire);
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intptr_t dif = (intptr_t)seq - (intptr_t)pos;
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if (dif == 0)
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{
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if (enqueue_pos_.compare_exchange_weak(pos, pos + 1, std::memory_order_relaxed))
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break;
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}
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else if (dif < 0)
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{
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return false;
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}
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else
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{
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pos = enqueue_pos_.load(std::memory_order_relaxed);
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}
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}
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cell->data_ = std::move(data);
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cell->sequence_.store(pos + 1, std::memory_order_release);
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return true;
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}
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bool dequeue(T& data)
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{
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cell_t* cell;
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size_t pos = dequeue_pos_.load(std::memory_order_relaxed);
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for (;;)
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{
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cell = &buffer_[pos & buffer_mask_];
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size_t seq =
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cell->sequence_.load(std::memory_order_acquire);
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intptr_t dif = (intptr_t)seq - (intptr_t)(pos + 1);
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if (dif == 0)
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{
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if (dequeue_pos_.compare_exchange_weak(pos, pos + 1, std::memory_order_relaxed))
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break;
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}
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else if (dif < 0)
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return false;
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else
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pos = dequeue_pos_.load(std::memory_order_relaxed);
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}
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data = std::move(cell->data_);
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cell->sequence_.store(pos + buffer_mask_ + 1, std::memory_order_release);
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return true;
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}
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size_t approx_size()
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{
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size_t first_pos = dequeue_pos_.load(std::memory_order_relaxed);
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size_t last_pos = enqueue_pos_.load(std::memory_order_relaxed);
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if (last_pos <= first_pos)
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return 0;
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auto size = last_pos - first_pos;
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return size < max_size_ ? size : max_size_;
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}
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private:
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struct cell_t
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{
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std::atomic<size_t> sequence_;
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T data_;
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};
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size_t const max_size_;
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static size_t const cacheline_size = 64;
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typedef char cacheline_pad_t [cacheline_size];
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cacheline_pad_t pad0_;
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cell_t* const buffer_;
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size_t const buffer_mask_;
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cacheline_pad_t pad1_;
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std::atomic<size_t> enqueue_pos_;
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cacheline_pad_t pad2_;
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std::atomic<size_t> dequeue_pos_;
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cacheline_pad_t pad3_;
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mpmc_bounded_queue(mpmc_bounded_queue const&) = delete;
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void operator= (mpmc_bounded_queue const&) = delete;
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};
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} // ns details
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} // ns spdlog
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