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/***
This file is part of snapcast
Copyright (C) 2014-2025 Johannes Pohl
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
***/
#pragma once
// standard headers
#include <algorithm>
#include <array>
#include <cstddef>
#include <cstdint>
#include <deque>
/// Size limited queue
/**
* Size limited queue with basic statistic functions:
* median, mean, percentile
*/
template <class T>
class DoubleBuffer
{
public:
/// c'tor
explicit DoubleBuffer(size_t size = 10) : bufferSize(size)
{
}
/// Add @p element, pop last, if buffer is full
inline void add(const T& element)
{
buffer.push_back(element);
if (buffer.size() > bufferSize)
buffer.pop_front();
}
/// Add @p element, pop last, if buffer is full
inline void add(T&& element)
{
buffer.push_back(std::move(element));
if (buffer.size() > bufferSize)
buffer.pop_front();
}
/// @return median as mean over N values around the median
T median(uint16_t mean = 1) const
{
if (buffer.empty())
return 0;
std::deque<T> tmpBuffer(buffer.begin(), buffer.end());
std::sort(tmpBuffer.begin(), tmpBuffer.end());
if ((mean <= 1) || (tmpBuffer.size() < mean))
return tmpBuffer[tmpBuffer.size() / 2];
else
{
uint16_t low = static_cast<uint16_t>(tmpBuffer.size()) / 2;
uint16_t high = low;
low -= mean / 2;
high += mean / 2;
T result((T)0);
for (uint16_t i = low; i <= high; ++i)
{
result += tmpBuffer[i];
}
return result / mean;
}
}
/// @return mean value
double mean() const
{
if (buffer.empty())
return 0;
double mean = 0.;
for (size_t n = 0; n < buffer.size(); ++n)
mean += (float)buffer[n] / (float)buffer.size();
return mean;
}
/// @return @p percentile percentile
T percentile(unsigned int percentile) const
{
if (buffer.empty())
return 0;
std::deque<T> tmpBuffer(buffer.begin(), buffer.end());
std::sort(tmpBuffer.begin(), tmpBuffer.end());
return tmpBuffer[(size_t)((tmpBuffer.size() - 1) * ((float)percentile / (float)100))];
}
/// @return array of different percentiles
template <std::size_t Size>
std::array<T, Size> percentiles(std::array<uint8_t, Size> percentiles) const
{
std::array<T, Size> result;
result.fill(0);
if (buffer.empty())
return result;
std::deque<T> tmpBuffer(buffer.begin(), buffer.end());
std::sort(tmpBuffer.begin(), tmpBuffer.end());
for (std::size_t i = 0; i < Size; ++i)
result[i] = tmpBuffer[(size_t)((tmpBuffer.size() - 1) * ((float)percentiles[i] / (float)100))];
return result;
}
/// @return if the buffer is full
inline bool full() const
{
return (buffer.size() == bufferSize);
}
/// Clear the buffer
inline void clear()
{
buffer.clear();
}
/// @return current size of the buffer
inline size_t size() const
{
return buffer.size();
}
/// @return if the buffer is empty
inline bool empty() const
{
return buffer.empty();
}
/// Set size of the buffer
void setSize(size_t size)
{
bufferSize = size;
}
/// @return the raw buffer
const std::deque<T>& getBuffer() const
{
return buffer;
}
private:
size_t bufferSize;
std::deque<T> buffer;
};
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