mirror of
https://github.com/ntop/ntopng.git
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99 lines
2.3 KiB
C++
99 lines
2.3 KiB
C++
/*
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*
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* (C) 2014-20 - ntop.org
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*
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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*/
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#ifndef _SPSC_QUEUE_H_
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#define _SPSC_QUEUE_H_
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#include "ntop_includes.h"
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/* Lockless fixed-size Single-Producer Single-Consumer queue */
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#define QUEUE_WATERMARK 8 /* pow of 2 */
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#define QUEUE_WATERMARK_MASK (QUEUE_WATERMARK - 1)
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template <typename T> class SPSCQueue {
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private:
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u_int64_t shadow_head;
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volatile u_int64_t head;
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volatile u_int64_t tail;
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u_int64_t shadow_tail;
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std::vector<T> queue;
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u_int32_t queue_size;
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public:
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SPSCQueue(u_int32_t size) {
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queue_size = Utils::pow2(size);
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queue.reserve(queue_size);
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tail = shadow_tail = queue_size-1;
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head = shadow_head = 0;
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}
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~SPSCQueue() { ; }
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inline bool isNotEmpty() {
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u_int32_t next_tail = (shadow_tail + 1) & (queue_size-1);
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return next_tail != head;
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}
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inline bool isFull() {
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u_int32_t next_head = (shadow_head + 1) & (queue_size-1);
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return tail == next_head;
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}
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inline T dequeue() {
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u_int32_t next_tail;
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next_tail = (shadow_tail + 1) & (queue_size-1);
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if (next_tail != head) {
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T item = queue[next_tail];
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shadow_tail = next_tail;
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if ((shadow_tail & QUEUE_WATERMARK_MASK) == 0)
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tail = shadow_tail;
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return item;
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}
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return static_cast<T>(NULL);
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}
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inline bool enqueue(T item, bool flush) {
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u_int32_t next_head;
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next_head = (shadow_head + 1) & (queue_size-1);
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if (tail != next_head) {
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queue[shadow_head] = item;
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shadow_head = next_head;
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if (flush || (shadow_head & QUEUE_WATERMARK_MASK) == 0)
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head = shadow_head;
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return true;
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}
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return false;
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}
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};
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#endif /* _SPSC_QUEUE_H_ */
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