67 lines
1.7 KiB
Go
67 lines
1.7 KiB
Go
|
// Package fastuuid provides fast UUID generation of 192 bit
|
||
|
|
// universally unique identifiers. It does not provide
|
||
|
|
// formatting or parsing of the identifiers (it is assumed
|
||
|
|
// that a simple hexadecimal or base64 representation
|
||
|
|
// is sufficient, for which adequate functionality exists elsewhere).
|
||
|
|
//
|
||
|
|
// Note that the generated UUIDs are not unguessable - each
|
||
|
|
// UUID generated from a Generator is adjacent to the
|
||
|
|
// previously generated UUID.
|
||
|
|
//
|
||
|
|
// It ignores RFC 4122.
|
||
|
|
package fastuuid
|
||
|
|
|
||
|
|
import (
|
||
|
|
"crypto/rand"
|
||
|
|
"encoding/binary"
|
||
|
|
"errors"
|
||
|
|
"sync/atomic"
|
||
|
|
)
|
||
|
|
|
||
|
|
// Generator represents a UUID generator that
|
||
|
|
// generates UUIDs in sequence from a random starting
|
||
|
|
// point.
|
||
|
|
type Generator struct {
|
||
|
|
seed [24]byte
|
||
|
|
counter uint64
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewGenerator returns a new Generator.
|
||
|
|
// It can fail if the crypto/rand read fails.
|
||
|
|
func NewGenerator() (*Generator, error) {
|
||
|
|
var g Generator
|
||
|
|
_, err := rand.Read(g.seed[:])
|
||
|
|
if err != nil {
|
||
|
|
return nil, errors.New("cannot generate random seed: " + err.Error())
|
||
|
|
}
|
||
|
|
return &g, nil
|
||
|
|
}
|
||
|
|
|
||
|
|
// MustNewGenerator is like NewGenerator
|
||
|
|
// but panics on failure.
|
||
|
|
func MustNewGenerator() *Generator {
|
||
|
|
g, err := NewGenerator()
|
||
|
|
if err != nil {
|
||
|
|
panic(err)
|
||
|
|
}
|
||
|
|
return g
|
||
|
|
}
|
||
|
|
|
||
|
|
// Next returns the next UUID from the generator.
|
||
|
|
// Only the first 8 bytes can differ from the previous
|
||
|
|
// UUID, so taking a slice of the first 16 bytes
|
||
|
|
// is sufficient to provide a somewhat less secure 128 bit UUID.
|
||
|
|
//
|
||
|
|
// It is OK to call this method concurrently.
|
||
|
|
func (g *Generator) Next() [24]byte {
|
||
|
|
x := atomic.AddUint64(&g.counter, 1)
|
||
|
|
var counterBytes [8]byte
|
||
|
|
binary.LittleEndian.PutUint64(counterBytes[:], x)
|
||
|
|
|
||
|
|
uuid := g.seed
|
||
|
|
for i, b := range counterBytes {
|
||
|
|
uuid[i] ^= b
|
||
|
|
}
|
||
|
|
return uuid
|
||
|
|
}
|