transmission/libtransmission/watchdir-base.h

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// This file Copyright © 2015-2023 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.
#ifndef LIBTRANSMISSION_WATCHDIR_MODULE
#error only the wathcdir module should #include this header.
#endif
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#pragma once
#include <algorithm>
#include <chrono>
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#include <cstddef> // for size_t
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#include <map>
#include <memory>
#include <optional>
#include <set>
#include <string>
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#include <string_view>
#include <utility>
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#include "timer.h"
#include "watchdir.h"
namespace libtransmission::impl
{
// base class for concrete tr_watchdirs
class BaseWatchdir : public Watchdir
{
public:
BaseWatchdir(std::string_view dirname, Callback callback, TimerMaker& timer_maker)
: dirname_{ dirname }
, callback_{ std::move(callback) }
, retry_timer_{ timer_maker.create() }
{
retry_timer_->setCallback([this]() { onRetryTimer(); });
}
BaseWatchdir(BaseWatchdir&&) = delete;
BaseWatchdir(BaseWatchdir const&) = delete;
BaseWatchdir& operator=(BaseWatchdir&&) = delete;
BaseWatchdir& operator=(BaseWatchdir const&) = delete;
[[nodiscard]] std::string_view dirname() const noexcept override
{
return dirname_;
}
[[nodiscard]] constexpr auto timeoutDuration() const noexcept
{
return timeout_duration_;
}
constexpr void setTimeoutDuration(std::chrono::seconds timeout_duration) noexcept
{
timeout_duration_ = timeout_duration;
}
[[nodiscard]] constexpr auto retryDuration() const noexcept
{
return retry_duration_;
}
void setRetryDuration(std::chrono::milliseconds retry_duration) noexcept
{
retry_duration_ = retry_duration;
for (auto& [basename, info] : pending_)
{
setNextKickTime(info);
}
}
protected:
void scan();
void processFile(std::string_view basename);
private:
using Timestamp = std::chrono::time_point<std::chrono::steady_clock>;
struct Pending
{
size_t strikes = 0U;
Timestamp first_kick_at = {};
Timestamp last_kick_at = {};
Timestamp next_kick_at = {};
};
void setNextKickTime(Pending& item)
{
item.next_kick_at = item.last_kick_at + retry_duration_;
}
[[nodiscard]] auto nextKickTime() const
{
auto next_time = std::optional<Timestamp>{};
for (auto const& [name, info] : pending_)
{
if (!next_time || info.next_kick_at < *next_time)
{
next_time = info.next_kick_at;
}
}
return next_time;
}
void restartTimerIfPending()
{
if (auto next_kick_time = nextKickTime(); next_kick_time)
{
using namespace std::chrono;
auto const now = steady_clock::now();
auto duration = duration_cast<milliseconds>(*next_kick_time - now);
retry_timer_->startSingleShot(duration);
}
}
void onRetryTimer()
{
using namespace std::chrono;
auto const now = steady_clock::now();
auto tmp = decltype(pending_){};
std::swap(tmp, pending_);
for (auto const& [basename, info] : tmp)
{
if (info.next_kick_at <= now)
{
processFile(basename);
}
else
{
pending_.try_emplace(basename, info);
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}
}
restartTimerIfPending();
}
std::string const dirname_;
Callback const callback_;
std::unique_ptr<Timer> const retry_timer_;
std::map<std::string, Pending, std::less<>> pending_;
std::set<std::string, std::less<>> handled_;
std::chrono::milliseconds retry_duration_ = std::chrono::seconds{ 5 };
std::chrono::seconds timeout_duration_ = std::chrono::seconds{ 15 };
};
} // namespace libtransmission::impl