transmission/libtransmission/history.h

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// This file Copyright © Mnemosyne LLC.
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// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#pragma once
#ifndef __TRANSMISSION__
#error only libtransmission should #include this header.
#endif
#include <array>
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#include <cstddef> // for size_t
#include <cstdint> // for uint32_t
#include <ctime> // for time_t
/**
* A short-term memory object that remembers how many times something
* happened over the last Seconds seconds. `tr_peer` uses it to count
* how many bytes transferred to estimate the speed over the last
* Seconds seconds.
*/
template<typename SizeType, std::size_t Seconds = 60>
class tr_recentHistory
{
public:
/**
* @brief add a counter to the recent history object.
* @param when the current time in sec, such as from tr_time()
* @param n how many items to add to the history's counter
*/
constexpr void add(time_t now, SizeType n)
{
if (timestamps_[newest_] != now)
{
newest_ = (newest_ + 1) % Seconds;
timestamps_[newest_] = now;
count_[newest_] = {};
}
count_[newest_] += n;
}
/**
* @brief count how many events have occurred in the last N seconds.
* @param when the current time in sec, such as from tr_time()
* @param seconds how many seconds to count back through.
*/
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[[nodiscard]] constexpr SizeType count(time_t now, unsigned int age_sec) const
{
auto sum = SizeType{};
time_t const oldest = now - age_sec;
for (std::size_t i = 0; i < Seconds; ++i)
{
if (timestamps_[i] >= oldest)
{
sum += count_[i];
}
}
return sum;
}
private:
std::array<time_t, Seconds> timestamps_ = {};
std::array<SizeType, Seconds> count_ = {};
uint32_t newest_ = 0;
};