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rocksdb/util/mpsc.h

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// Portions Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
// Large parts of this file is borrowed from the public domain code below.
// from https://github.com/mstump/queues
// C++ implementation of Dmitry Vyukov's non-intrusive
// lock free unbound MPSC queue
// http://www.1024cores.net/home/
// lock-free-algorithms/queues/non-intrusive-mpsc-node-based-queue
// License from mstump/queues
// This is free and unencumbered software released into the public domain.
//
// Anyone is free to copy, modify, publish, use, compile, sell, or
// distribute this software, either in source code form or as a compiled
// binary, for any purpose, commercial or non-commercial, and by any
// means.
//
// In jurisdictions that recognize copyright laws, the author or authors
// of this software dedicate any and all copyright interest in the
// software to the public domain. We make this dedication for the benefit
// of the public at large and to the detriment of our heirs and
// successors. We intend this dedication to be an overt act of
// relinquishment in perpetuity of all present and future rights to this
// software under copyright law.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
// OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
//
// For more information, please refer to <http://unlicense.org>
// License from http://www.1024cores.net/home/
// lock-free-algorithms/queues/non-intrusive-mpsc-node-based-queue
// Copyright (c) 2010-2011 Dmitry Vyukov. All rights reserved.
// Redistribution and use in source and binary forms, with or
// without modification, are permitted provided that the following
// conditions are met:
// 1. Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY DMITRY VYUKOV "AS IS" AND ANY EXPRESS OR
// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
// EVENT SHALL DMITRY VYUKOV OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
// USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// The views and conclusions contained in the software and documentation
// are those of the authors and should not be interpreted as representing
// official policies, either expressed or implied, of Dmitry Vyukov.
//
#ifndef UTIL_MPSC_H_
#define UTIL_MPSC_H_
#include <atomic>
#include <cassert>
#include <type_traits>
/**
* Multiple Producer Single Consumer Lockless Q
*/
template <typename T>
class mpsc_queue_t {
public:
struct buffer_node_t {
T data;
std::atomic<buffer_node_t*> next;
};
mpsc_queue_t() {
buffer_node_aligned_t* al_st = new buffer_node_aligned_t;
buffer_node_t* node = new (al_st) buffer_node_t();
_head.store(node);
_tail.store(node);
node->next.store(nullptr, std::memory_order_relaxed);
}
~mpsc_queue_t() {
T output;
while (this->dequeue(&output)) {
}
buffer_node_t* front = _head.load(std::memory_order_relaxed);
front->~buffer_node_t();
::operator delete(front);
}
void enqueue(const T& input) {
buffer_node_aligned_t* al_st = new buffer_node_aligned_t;
buffer_node_t* node = new (al_st) buffer_node_t();
node->data = input;
node->next.store(nullptr, std::memory_order_relaxed);
buffer_node_t* prev_head = _head.exchange(node, std::memory_order_acq_rel);
prev_head->next.store(node, std::memory_order_release);
}
bool dequeue(T* output) {
buffer_node_t* tail = _tail.load(std::memory_order_relaxed);
buffer_node_t* next = tail->next.load(std::memory_order_acquire);
if (next == nullptr) {
return false;
}
*output = next->data;
_tail.store(next, std::memory_order_release);
tail->~buffer_node_t();
::operator delete(tail);
return true;
}
// you can only use pop_all if the queue is SPSC
buffer_node_t* pop_all() {
// nobody else can move the tail pointer.
buffer_node_t* tptr = _tail.load(std::memory_order_relaxed);
buffer_node_t* next =
tptr->next.exchange(nullptr, std::memory_order_acquire);
_head.exchange(tptr, std::memory_order_acquire);
// there is a race condition here
return next;
}
private:
typedef typename std::aligned_storage<
sizeof(buffer_node_t), std::alignment_of<buffer_node_t>::value>::type
buffer_node_aligned_t;
std::atomic<buffer_node_t*> _head;
std::atomic<buffer_node_t*> _tail;
mpsc_queue_t(const mpsc_queue_t&) = delete;
mpsc_queue_t& operator=(const mpsc_queue_t&) = delete;
};
#endif // UTIL_MPSC_H_