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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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