key_encoding.go

package main

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

// Layout: [8 bytes: unix timestamp][4 bytes: sequence id]
// Properties:
// * byte representation ordered chronologically & lexicographically
// * allows inserting out of chronological order
// * seeking to a Key{Seq: 0, Time: ts} will find the first record with the specified timestamp

var order = binary.LittleEndian

type Key struct {
	Seq  uint32
	Time time.Time
}

func ParseKey(buf []byte) (*Key, error) {
	if len(buf) != 12 {
		return nil, fmt.Errorf("key buffer must be 12 bytes")
	}
	ts := int64(order.Uint64(buf[:8]))
	return &Key{
		Seq:  order.Uint32(buf[8:]),
		Time: time.Unix(ts, 0),
	}, nil
}

func (k *Key) Bytes() []byte {
	buf := make([]byte, 12)
	order.PutUint32(buf[8:], k.Seq)
	order.PutUint64(buf[:8], uint64(k.Time.Unix()))
	return buf
}

func main() {
	k1 := &Key{
		Seq:  123,
		Time: time.Now(),
	}
	buf := k1.Bytes()
	k2, err := ParseKey(buf)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("%v, %v\n", k1, k2)
}