mirror of
https://github.com/zerotier/ZeroTierOne.git
synced 2024-12-23 14:52:24 +00:00
337 lines
7.4 KiB
C++
337 lines
7.4 KiB
C++
/*
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* Copyright (c)2013-2020 ZeroTier, Inc.
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*
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* Use of this software is governed by the Business Source License included
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* in the LICENSE.TXT file in the project's root directory.
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*
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* Change Date: 2025-01-01
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*
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* On the date above, in accordance with the Business Source License, use
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* of this software will be governed by version 2.0 of the Apache License.
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*/
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/****/
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#ifndef ZT_RINGBUFFER_H
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#define ZT_RINGBUFFER_H
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#include <typeinfo>
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#include <cstdint>
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#include <stdlib.h>
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#include <memory.h>
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#include <algorithm>
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#include <math.h>
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namespace ZeroTier {
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/**
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* A circular buffer
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*
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* For fast handling of continuously-evolving variables (such as path quality metrics).
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* Using this, we can maintain longer sliding historical windows for important path
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* metrics without the need for potentially expensive calls to memcpy/memmove.
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*
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* Some basic statistical functionality is implemented here in an attempt
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* to reduce the complexity of code needed to interact with this type of buffer.
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*/
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template <class T,size_t S>
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class RingBuffer
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{
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private:
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T buf[S];
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size_t begin;
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size_t end;
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bool wrap;
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public:
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RingBuffer() :
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begin(0),
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end(0),
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wrap(false)
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{
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memset(buf,0,sizeof(T)*S);
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}
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/**
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* @return A pointer to the underlying buffer
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*/
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inline T *get_buf()
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{
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return buf + begin;
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}
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/**
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* Adjust buffer index pointer as if we copied data in
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* @param n Number of elements to copy in
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* @return Number of elements we copied in
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*/
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inline size_t produce(size_t n)
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{
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n = std::min(n, getFree());
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if (n == 0) {
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return n;
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}
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const size_t first_chunk = std::min(n, S - end);
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end = (end + first_chunk) % S;
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if (first_chunk < n) {
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const size_t second_chunk = n - first_chunk;
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end = (end + second_chunk) % S;
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}
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if (begin == end) {
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wrap = true;
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}
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return n;
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}
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/**
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* Fast erase, O(1).
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* Merely reset the buffer pointer, doesn't erase contents
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*/
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inline void reset() { consume(count()); }
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/**
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* adjust buffer index pointer as if we copied data out
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* @param n Number of elements we copied from the buffer
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* @return Number of elements actually available from the buffer
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*/
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inline size_t consume(size_t n)
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{
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n = std::min(n, count());
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if (n == 0) {
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return n;
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}
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if (wrap) {
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wrap = false;
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}
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const size_t first_chunk = std::min(n, S - begin);
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begin = (begin + first_chunk) % S;
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if (first_chunk < n) {
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const size_t second_chunk = n - first_chunk;
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begin = (begin + second_chunk) % S;
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}
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return n;
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}
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/**
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* @param data Buffer that is to be written to the ring
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* @param n Number of elements to write to the buffer
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*/
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inline size_t write(const T * data, size_t n)
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{
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n = std::min(n, getFree());
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if (n == 0) {
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return n;
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}
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const size_t first_chunk = std::min(n, S - end);
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memcpy(buf + end, data, first_chunk * sizeof(T));
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end = (end + first_chunk) % S;
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if (first_chunk < n) {
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const size_t second_chunk = n - first_chunk;
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memcpy(buf + end, data + first_chunk, second_chunk * sizeof(T));
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end = (end + second_chunk) % S;
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}
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if (begin == end) {
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wrap = true;
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}
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return n;
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}
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/**
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* Place a single value on the buffer. If the buffer is full, consume a value first.
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*
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* @param value A single value to be placed in the buffer
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*/
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inline void push(const T value)
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{
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if (count() == S) {
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consume(1);
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}
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const size_t first_chunk = std::min((size_t)1, S - end);
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*(buf + end) = value;
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end = (end + first_chunk) % S;
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if (begin == end) {
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wrap = true;
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}
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}
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/**
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* @return The most recently pushed element on the buffer
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*/
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inline T get_most_recent() { return *(buf + end); }
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/**
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* @param dest Destination buffer
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* @param n Size (in terms of number of elements) of the destination buffer
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* @return Number of elements read from the buffer
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*/
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inline size_t read(T *dest,size_t n)
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{
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n = std::min(n, count());
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if (n == 0) {
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return n;
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}
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if (wrap) {
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wrap = false;
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}
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const size_t first_chunk = std::min(n, S - begin);
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memcpy(dest, buf + begin, first_chunk * sizeof(T));
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begin = (begin + first_chunk) % S;
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if (first_chunk < n) {
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const size_t second_chunk = n - first_chunk;
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memcpy(dest + first_chunk, buf + begin, second_chunk * sizeof(T));
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begin = (begin + second_chunk) % S;
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}
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return n;
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}
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/**
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* Return how many elements are in the buffer, O(1).
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*
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* @return The number of elements in the buffer
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*/
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inline size_t count()
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{
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if (end == begin) {
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return wrap ? S : 0;
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}
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else if (end > begin) {
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return end - begin;
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}
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else {
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return S + end - begin;
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}
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}
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/**
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* @return The number of slots that are unused in the buffer
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*/
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inline size_t getFree() { return S - count(); }
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/**
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* @return The arithmetic mean of the contents of the buffer
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*/
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inline float mean()
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{
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size_t iterator = begin;
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float subtotal = 0;
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size_t curr_cnt = count();
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for (size_t i=0; i<curr_cnt; i++) {
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iterator = (iterator + S - 1) % curr_cnt;
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subtotal += (float)*(buf + iterator);
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}
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return curr_cnt ? subtotal / (float)curr_cnt : 0;
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}
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/**
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* @return The arithmetic mean of the most recent 'n' elements of the buffer
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*/
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inline float mean(size_t n)
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{
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n = n < S ? n : S;
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size_t iterator = begin;
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float subtotal = 0;
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size_t curr_cnt = count();
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for (size_t i=0; i<n; i++) {
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iterator = (iterator + S - 1) % curr_cnt;
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subtotal += (float)*(buf + iterator);
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}
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return curr_cnt ? subtotal / (float)curr_cnt : 0;
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}
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/**
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* @return The sum of the contents of the buffer
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*/
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inline float sum()
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{
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size_t iterator = begin;
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float total = 0;
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size_t curr_cnt = count();
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for (size_t i=0; i<curr_cnt; i++) {
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iterator = (iterator + S - 1) % curr_cnt;
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total += (float)*(buf + iterator);
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}
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return total;
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}
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/**
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* @return The sample standard deviation of element values
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*/
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inline float stddev() { return sqrt(variance()); }
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/**
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* @return The variance of element values
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*/
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inline float variance()
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{
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size_t iterator = begin;
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float cached_mean = mean();
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size_t curr_cnt = count();
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T sum_of_squared_deviations = 0;
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for (size_t i=0; i<curr_cnt; i++) {
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iterator = (iterator + S - 1) % curr_cnt;
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float deviation = (buf[i] - cached_mean);
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sum_of_squared_deviations += (T)(deviation*deviation);
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}
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float variance = (float)sum_of_squared_deviations / (float)(S - 1);
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return variance;
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}
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/**
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* @return The number of elements of zero value
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*/
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inline size_t zeroCount()
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{
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size_t iterator = begin;
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size_t zeros = 0;
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size_t curr_cnt = count();
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for (size_t i=0; i<curr_cnt; i++) {
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iterator = (iterator + S - 1) % curr_cnt;
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if (*(buf + iterator) == 0) {
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zeros++;
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}
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}
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return zeros;
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}
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/**
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* @param value Value to match against in buffer
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* @return The number of values held in the ring buffer which match a given value
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*/
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inline size_t countValue(T value)
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{
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size_t iterator = begin;
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size_t cnt = 0;
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size_t curr_cnt = count();
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for (size_t i=0; i<curr_cnt; i++) {
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iterator = (iterator + S - 1) % curr_cnt;
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if (*(buf + iterator) == value) {
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cnt++;
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}
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}
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return cnt;
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}
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/**
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* Print the contents of the buffer
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*/
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/*
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inline void dump()
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{
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size_t iterator = begin;
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for (size_t i=0; i<S; i++) {
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iterator = (iterator + S - 1) % S;
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if (typeid(T) == typeid(int)) {
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fprintf(stderr, "buf[%2zu]=%2d\n", iterator, (int)*(buf + iterator));
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}
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else {
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fprintf(stderr, "buf[%2zu]=%2f\n", iterator, (float)*(buf + iterator));
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}
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}
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}
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*/
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};
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} // namespace ZeroTier
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#endif
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