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/*
* ZeroTier One - Network Virtualization Everywhere
* Copyright (C) 2011-2015 ZeroTier, Inc.
*
* 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/>.
*
* --
*
* ZeroTier may be used and distributed under the terms of the GPLv3, which
* are available at: http://www.gnu.org/licenses/gpl-3.0.html
*
* If you would like to embed ZeroTier into a commercial application or
* redistribute it in a modified binary form, please contact ZeroTier Networks
* LLC. Start here: http://www.zerotier.com/
*/
#ifndef ZT_BWACCOUNT_HPP
#define ZT_BWACCOUNT_HPP
#include <stdint.h>
#include <math.h>
#include "Constants.hpp"
#include "Utils.hpp"
#ifdef __WINDOWS__
#define round(x) ((x-floor(x))>0.5 ? ceil(x) : floor(x))
#endif
namespace ZeroTier {
/**
* Bandwidth account used for rate limiting multicast groups
*
* This is used to apply a bank account model to multicast groups. Each
* multicast packet counts against a balance, which accrues at a given
* rate in bytes per second. Debt is possible. These parameters are
* configurable.
*
* A bank account model permits bursting behavior, which correctly models
* how OSes and apps typically use multicast. It's common for things to
* spew lots of multicast messages at once, wait a while, then do it
* again. A consistent bandwidth limit model doesn't fit.
*/
class BandwidthAccount
{
public:
/**
* Create an uninitialized account
*
* init() must be called before this is used.
*/
BandwidthAccount() throw() {}
/**
* Create and initialize
*
* @param preload Initial balance to place in account
* @param maxb Maximum allowed balance (> 0)
* @param acc Rate of accrual in bytes per second
* @param now Current time
*/
BandwidthAccount(uint32_t preload,uint32_t maxb,uint32_t acc,uint64_t now)
throw()
{
init(preload,maxb,acc,now);
}
/**
* Initialize or re-initialize account
*
* @param preload Initial balance to place in account
* @param maxb Maximum allowed balance (> 0)
* @param acc Rate of accrual in bytes per second
* @param now Current time
*/
inline void init(uint32_t preload,uint32_t maxb,uint32_t acc,uint64_t now)
throw()
{
_lastTime = ((double)now / 1000.0);
_balance = preload;
_maxBalance = maxb;
_accrual = acc;
}
/**
* Update and retrieve balance of this account
*
* @param now Current time
* @return New balance updated from current clock
*/
inline uint32_t update(uint64_t now)
throw()
{
double lt = _lastTime;
double nowf = ((double)now / 1000.0);
_lastTime = nowf;
return (_balance = std::min(_maxBalance,(uint32_t)round((double)_balance + ((double)_accrual * (nowf - lt)))));
}
/**
* Update balance and conditionally deduct
*
* If the deduction amount fits, it is deducted after update. Otherwise
* balance is updated and false is returned.
*
* @param amt Amount to deduct
* @param now Current time
* @return True if amount fit within balance and was deducted
*/
inline bool deduct(uint32_t amt,uint64_t now)
throw()
{
if (update(now) >= amt) {
_balance -= amt;
return true;
}
return false;
}
/**
* @return Most recent balance without update
*/
inline uint32_t balance() const
throw()
{
return _balance;
}
private:
double _lastTime;
uint32_t _balance;
uint32_t _maxBalance;
uint32_t _accrual;
};
} // namespace ZeroTier
#endif
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