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// Copyright 2016 Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package uuid
import "io"
// New creates a new random UUID or panics. New is equivalent to
// the expression
//
// uuid.Must(uuid.NewRandom())
func New() UUID {
return Must(NewRandom())
}
// NewString creates a new random UUID and returns it as a string or panics.
// NewString is equivalent to the expression
//
// uuid.New().String()
func NewString() string {
return Must(NewRandom()).String()
}
// NewRandom returns a Random (Version 4) UUID.
//
// The strength of the UUIDs is based on the strength of the crypto/rand
// package.
//
// Uses the randomness pool if it was enabled with EnableRandPool.
//
// A note about uniqueness derived from the UUID Wikipedia entry:
//
// Randomly generated UUIDs have 122 random bits. One's annual risk of being
// hit by a meteorite is estimated to be one chance in 17 billion, that
// means the probability is about 0.00000000006 (6 × 10−11),
// equivalent to the odds of creating a few tens of trillions of UUIDs in a
// year and having one duplicate.
func NewRandom() (UUID, error) {
if !poolEnabled {
return NewRandomFromReader(rander)
}
return newRandomFromPool()
}
// NewRandomFromReader returns a UUID based on bytes read from a given io.Reader.
func NewRandomFromReader(r io.Reader) (UUID, error) {
var uuid UUID
_, err := io.ReadFull(r, uuid[:])
if err != nil {
return Nil, err
}
uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4
uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10
return uuid, nil
}
func newRandomFromPool() (UUID, error) {
var uuid UUID
poolMu.Lock()
if poolPos == randPoolSize {
_, err := io.ReadFull(rander, pool[:])
if err != nil {
poolMu.Unlock()
return Nil, err
}
poolPos = 0
}
copy(uuid[:], pool[poolPos:(poolPos+16)])
poolPos += 16
poolMu.Unlock()
uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4
uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10
return uuid, nil
}
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