request_id.go

package main

import (
	"crypto/rand"
	"encoding/binary"
	"encoding/hex"
	"fmt"
	"io"
	"sync/atomic"
	"time"
)

// newMongoID - генерация нового MongoID
func newMongoID() string {
	return newObjectIDFromTimestamp(time.Now()).hex()
}

var processUnique = processUniqueBytes()
var objectIDCounter = readRandomUint32()

type ObjectID [12]byte

func putUint24(b []byte, v uint32) {
	b[0] = byte(v >> 16)
	b[1] = byte(v >> 8)
	b[2] = byte(v)
}

func readRandomUint32() uint32 {
	var b [4]byte
	_, err := io.ReadFull(rand.Reader, b[:])
	if err != nil {
		panic(fmt.Errorf("cannot initialize objectid package with crypto.rand.Reader: %v", err))
	}

	return (uint32(b[0]) << 0) | (uint32(b[1]) << 8) | (uint32(b[2]) << 16) | (uint32(b[3]) << 24)
}

func newObjectIDFromTimestamp(timestamp time.Time) ObjectID {
	var b [12]byte

	binary.BigEndian.PutUint32(b[0:4], uint32(timestamp.Unix()))
	copy(b[4:9], processUnique[:])
	putUint24(b[9:12], atomic.AddUint32(&objectIDCounter, 1))

	return b
}

func (id ObjectID) hex() string {
	return hex.EncodeToString(id[:])
}

// timestamp extracts the time part of the ObjectId.
func (id ObjectID) timestamp() time.Time {
	unixSecs := binary.BigEndian.Uint32(id[0:4])
	return time.Unix(int64(unixSecs), 0).UTC()
}

func processUniqueBytes() [5]byte {
	var b [5]byte
	_, err := io.ReadFull(rand.Reader, b[:])
	if err != nil {
		panic(fmt.Errorf("cannot initialize objectid package with crypto.rand.Reader: %v", err))
	}

	return b
}