LedgerTiming.h

//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2012, 2013 Ripple Labs Inc.
 
    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.
 
    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================
 
#ifndef RIPPLE_APP_LEDGER_LEDGERTIMING_H_INCLUDED
#define RIPPLE_APP_LEDGER_LEDGERTIMING_H_INCLUDED
 
#include <ripple/basics/chrono.h>
#include <ripple/beast/utility/Journal.h>
#include <chrono>
#include <cstdint>
 
namespace ripple {
 
std::chrono::seconds constexpr ledgerPossibleTimeResolutions[] = {
    std::chrono::seconds{10},
    std::chrono::seconds{20},
    std::chrono::seconds{30},
    std::chrono::seconds{60},
    std::chrono::seconds{90},
    std::chrono::seconds{120}};
 
auto constexpr ledgerDefaultTimeResolution = ledgerPossibleTimeResolutions[2];
 
auto constexpr ledgerGenesisTimeResolution = ledgerPossibleTimeResolutions[0];
 
auto constexpr increaseLedgerTimeResolutionEvery = 8;
 
auto constexpr decreaseLedgerTimeResolutionEvery = 1;
 
template <class Rep, class Period, class Seq>
std::chrono::duration<Rep, Period>
getNextLedgerTimeResolution(
    std::chrono::duration<Rep, Period> previousResolution,
    bool previousAgree,
    Seq ledgerSeq)
{
    assert(ledgerSeq != Seq{0});
 
    using namespace std::chrono;
    // Find the current resolution:
    auto iter = std::find(
        std::begin(ledgerPossibleTimeResolutions),
        std::end(ledgerPossibleTimeResolutions),
        previousResolution);
    assert(iter != std::end(ledgerPossibleTimeResolutions));
 
    // This should never happen, but just as a precaution
    if (iter == std::end(ledgerPossibleTimeResolutions))
        return previousResolution;
 
    // If we did not previously agree, we try to decrease the resolution to
    // improve the chance that we will agree now.
    if (!previousAgree &&
        (ledgerSeq % Seq{decreaseLedgerTimeResolutionEvery} == Seq{0}))
    {
        if (++iter != std::end(ledgerPossibleTimeResolutions))
            return *iter;
    }
 
    // If we previously agreed, we try to increase the resolution to determine
    // if we can continue to agree.
    if (previousAgree &&
        (ledgerSeq % Seq{increaseLedgerTimeResolutionEvery} == Seq{0}))
    {
        if (iter-- != std::begin(ledgerPossibleTimeResolutions))
            return *iter;
    }
 
    return previousResolution;
}
 
template <class Clock, class Duration, class Rep, class Period>
std::chrono::time_point<Clock, Duration>
roundCloseTime(
    std::chrono::time_point<Clock, Duration> closeTime,
    std::chrono::duration<Rep, Period> closeResolution)
{
    using time_point = decltype(closeTime);
    if (closeTime == time_point{})
        return closeTime;
 
    closeTime += (closeResolution / 2);
    return closeTime - (closeTime.time_since_epoch() % closeResolution);
}
 
template <class Clock, class Duration, class Rep, class Period>
std::chrono::time_point<Clock, Duration>
effCloseTime(
    std::chrono::time_point<Clock, Duration> closeTime,
    std::chrono::duration<Rep, Period> resolution,
    std::chrono::time_point<Clock, Duration> priorCloseTime)
{
    using namespace std::chrono_literals;
    using time_point = decltype(closeTime);
 
    if (closeTime == time_point{})
        return closeTime;
 
    return std::max<time_point>(
        roundCloseTime(closeTime, resolution), (priorCloseTime + 1s));
}
 
}  // namespace ripple
#endif