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package id
import (
"crypto/rand"
"math/big"
"time"
"github.com/oklog/ulid"
)
const randomRange = 631152381 // ~20 years in seconds
// ULID represents a Universally Unique Lexicographically Sortable Identifier of 26 characters. See https://github.com/oklog/ulid
type ULID string
// NewULID returns a new ULID string using the current time, or an error if something goes wrong.
func NewULID() (string, error) {
newUlid, err := ulid.New(ulid.Timestamp(time.Now()), rand.Reader)
if err != nil {
return "", err
}
return newUlid.String(), nil
}
// NewULIDFromTime returns a new ULID string using the given time, or an error if something goes wrong.
func NewULIDFromTime(t time.Time) (string, error) {
newUlid, err := ulid.New(ulid.Timestamp(t), rand.Reader)
if err != nil {
return "", err
}
return newUlid.String(), nil
}
// NewRandomULID returns a new ULID string using a random time in an ~80 year range around the current datetime, or an error if something goes wrong.
func NewRandomULID() (string, error) {
b1, err := rand.Int(rand.Reader, big.NewInt(randomRange))
if err != nil {
return "", err
}
r1 := time.Duration(int(b1.Int64()))
b2, err := rand.Int(rand.Reader, big.NewInt(randomRange))
if err != nil {
return "", err
}
r2 := -time.Duration(int(b2.Int64()))
arbitraryTime := time.Now().Add(r1 * time.Second).Add(r2 * time.Second)
newUlid, err := ulid.New(ulid.Timestamp(arbitraryTime), rand.Reader)
if err != nil {
return "", err
}
return newUlid.String(), nil
}
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