NtpTimestamp.h

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#pragma once
#include <NDEVR/Time.h>
#include <QtCore/QtGlobal>
#include <QtCore/QtEndian>
#include <QtCore/QDateTime>
 
namespace NDEVR
{
#pragma pack(push, 1)
    /**
     * 64-bit NTP timestamp.
     */
    struct NtpTimestamp {
        /** Number of seconds passed since Jan 1 1900, in big-endian format. */
        quint32 seconds;
 
        /** Fractional time part, in <tt>1/0xFFFFFFFF</tt>s of a second. */
        quint32 fraction;
 
        NtpTimestamp() {};
        /**
        * @param dateTime The Time to convert to NTP structure.
        */
        NtpTimestamp(const Time& dateTime)
        {
            /* Convert given time to number of milliseconds passed since Jan 1 1900. */
            qint64 ntpMSecs = dateTime.getMilliseconds() + 2208988800000ULL;
 
            /* Note that NTP epoch information is lost here. Assume 1900-2036 NTP epoch. */
            quint32 s = ntpMSecs / 1000;
            quint32 f = 0x100000000ll * (ntpMSecs % 1000) / 1000;
 
            /* Convert to big-endian. */
            seconds = qToBigEndian(s);
            fraction = qToBigEndian(f);
        }
 
        /**
         * @returns Time object for the given NTP timestamp.
         */
        Time toTime() const
        {
            /* Convert to local-endian. */
            quint32 s = qFromBigEndian(seconds);
            quint32 f = qFromBigEndian(fraction);
 
            /* Convert NTP timestamp to number of milliseconds passed since Jan 1 1900. */
            qint64 ntpMSecs = s * 1000ll + f * 1000ll / 0x100000000ll;
 
            /* Construct Qt date time. */
            return Time(Time::MILLISECOND * (ntpMSecs - 2208988800000LL));
        }
    };
    static_assert(sizeof(NtpTimestamp) == 8);
#pragma pack(pop)
}