packedtimeandcounter.go

package main

import (
    "time"
)
type ReadState uint64

func (rs *ReadState) UnreadCounts() uint8 {
    return uint8(*rs >> 56)
}

func (rs *ReadState) SetCount(count uint8) {
    sec, ns := timestamp(*rs)
    *rs = pack(sec, ns, count)
}
func (rs *ReadState) SetLastRead(lastRead time.Time) {
    sec, us := toUnixSecondsAndMicroseconds(lastRead)
    *rs = pack(sec, us, rs.UnreadCounts())
}

func (rs *ReadState) LastRead() time.Time {
    sec, us := timestamp(*rs)
    return time.Unix(int64(sec), int64(us*1000))
}

func timestamp(rs ReadState) (sec uint32, us uint32) {
    sec = uint32(rs & 0xFFFFFFFF) //low
    us = uint32(rs >> 32)         //high
    //clear (counter) last 8 bit
    us &^= 1 << 31
    us &^= 1 << 30
    us &^= 1 << 29
    us &^= 1 << 28
    us &^= 1 << 27
    us &^= 1 << 26
    us &^= 1 << 25
    us &^= 1 << 24
    return sec, us
}

func NewReadStateUint(count uint8, lastRead time.Time) ReadState {
    seconds, microseconds := toUnixSecondsAndMicroseconds(lastRead)
    return pack(seconds, microseconds, count)
}

func toUnixSecondsAndMicroseconds(lastRead time.Time) (uint32, uint32) {
    microseconds := uint32((lastRead.Nanosecond()) / 1000)
    seconds := uint32(lastRead.Unix())
    return uint32(seconds), microseconds
}

func pack(seconds uint32, microseconds uint32, count uint8) ReadState {
    return ReadState(
        //unix seconds
        uint64(seconds) | uint64(seconds>>8)<<8 | uint64(seconds>>16)<<16 | uint64(seconds<<24)<<24 |
            //microseconds
            uint64(microseconds)<<32 | uint64(microseconds>>8)<<40 | uint64(microseconds>>16)<<48 |
            //counter
            uint64(count)<<56,
    )
}