offset.go

package wal

import (
	"encoding/binary"
	"fmt"
	"time"
)

const (
	// OffsetSize is the size in bytes of a WAL offset
	OffsetSize = 16
)

// Offset records an offset in the WAL
type Offset []byte

// NewOffsetForTS creates an offset for a given timestamp.
func NewOffsetForTS(ts time.Time) Offset {
	return NewOffset(tsToFileSequence(ts), 0)
}

func NewOffset(fileSequence int64, position int64) Offset {
	o := make(Offset, OffsetSize)
	binary.BigEndian.PutUint64(o, uint64(fileSequence))
	binary.BigEndian.PutUint64(o[8:], uint64(position))
	return o
}

func (o Offset) FileSequence() int64 {
	if len(o) == 0 {
		return 0
	}
	return int64(binary.BigEndian.Uint64(o))
}

func (o Offset) Position() int64 {
	if len(o) == 0 {
		return 0
	}
	return int64(binary.BigEndian.Uint64(o[8:]))
}

func (o Offset) TS() time.Time {
	return sequenceToTime(o.FileSequence())
}

func (a Offset) After(b Offset) bool {
	sequenceA := a.FileSequence()
	sequenceB := b.FileSequence()
	if sequenceA > sequenceB {
		return true
	}
	if sequenceA < sequenceB {
		return false
	}

	positionA := a.Position()
	positionB := b.Position()
	return positionA > positionB
}

func (o Offset) String() string {
	return fmt.Sprintf("%d:%d", o.FileSequence(), o.Position())
}