premiere-libtorrent/include/libtorrent/bandwidth_limit.hpp

/*

Copyright (c) 2007-2016, Arvid Norberg
All rights reserved.

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modification, are permitted provided that the following conditions
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      the documentation and/or other materials provided with the distribution.
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      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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*/

#ifndef TORRENT_BANDWIDTH_CHANNEL_HPP_INCLUDED
#define TORRENT_BANDWIDTH_CHANNEL_HPP_INCLUDED

#include <cstdint>
#include <limits>

#include "libtorrent/assert.hpp"

namespace libtorrent {

// member of peer_connection
struct TORRENT_EXTRA_EXPORT bandwidth_channel
{
	static constexpr int inf = (std::numeric_limits<std::int32_t>::max)();

	bandwidth_channel();

	// 0 means infinite
	void throttle(int limit);
	int throttle() const
	{
		TORRENT_ASSERT_VAL(m_limit >= 0, m_limit);
		TORRENT_ASSERT_VAL(m_limit < inf, m_limit);
		return m_limit;
	}

	int quota_left() const;
	void update_quota(int dt_milliseconds);

	// this is used when connections disconnect with
	// some quota left. It's returned to its bandwidth
	// channels.
	void return_quota(int amount);
	void use_quota(int amount);

	// this is an optimization. If there is more than one second
	// of quota built up in this channel, just apply it right away
	// instead of introducing a delay to split it up evenly. This
	// should especially help in situations where a single peer
	// has a capacity under the rate limit, but would otherwise be
	// held back by the latency of getting bandwidth from the limiter
	bool need_queueing(int amount)
	{
		if (m_quota_left - amount < m_limit) return true;
		m_quota_left -= amount;
		return false;
	}

	// used as temporary storage while distributing
	// bandwidth
	int tmp;

	// this is the number of bytes to distribute this round
	int distribute_quota;

private:

	// this is the amount of bandwidth we have
	// been assigned without using yet.
	std::int64_t m_quota_left;

	// the limit is the number of bytes
	// per second we are allowed to use.
	std::int32_t m_limit;
};

}

#endif