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divyadesai19009132020-03-04 12:58:08 +00001// Copyright 2016 Google Inc. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package uuid
6
7import "io"
8
9// New creates a new random UUID or panics. New is equivalent to
10// the expression
11//
12// uuid.Must(uuid.NewRandom())
13func New() UUID {
14 return Must(NewRandom())
15}
16
David K. Bainbridgebd6b2882021-08-26 13:31:02 +000017// NewString creates a new random UUID and returns it as a string or panics.
18// NewString is equivalent to the expression
19//
20// uuid.New().String()
21func NewString() string {
22 return Must(NewRandom()).String()
23}
24
divyadesai19009132020-03-04 12:58:08 +000025// NewRandom returns a Random (Version 4) UUID.
26//
27// The strength of the UUIDs is based on the strength of the crypto/rand
28// package.
29//
David K. Bainbridgebd6b2882021-08-26 13:31:02 +000030// Uses the randomness pool if it was enabled with EnableRandPool.
31//
divyadesai19009132020-03-04 12:58:08 +000032// A note about uniqueness derived from the UUID Wikipedia entry:
33//
34// Randomly generated UUIDs have 122 random bits. One's annual risk of being
35// hit by a meteorite is estimated to be one chance in 17 billion, that
36// means the probability is about 0.00000000006 (6 × 10−11),
37// equivalent to the odds of creating a few tens of trillions of UUIDs in a
38// year and having one duplicate.
39func NewRandom() (UUID, error) {
David K. Bainbridgebd6b2882021-08-26 13:31:02 +000040 if !poolEnabled {
41 return NewRandomFromReader(rander)
42 }
43 return newRandomFromPool()
44}
45
46// NewRandomFromReader returns a UUID based on bytes read from a given io.Reader.
47func NewRandomFromReader(r io.Reader) (UUID, error) {
divyadesai19009132020-03-04 12:58:08 +000048 var uuid UUID
David K. Bainbridgebd6b2882021-08-26 13:31:02 +000049 _, err := io.ReadFull(r, uuid[:])
divyadesai19009132020-03-04 12:58:08 +000050 if err != nil {
51 return Nil, err
52 }
53 uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4
54 uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10
55 return uuid, nil
56}
David K. Bainbridgebd6b2882021-08-26 13:31:02 +000057
58func newRandomFromPool() (UUID, error) {
59 var uuid UUID
60 poolMu.Lock()
61 if poolPos == randPoolSize {
62 _, err := io.ReadFull(rander, pool[:])
63 if err != nil {
64 poolMu.Unlock()
65 return Nil, err
66 }
67 poolPos = 0
68 }
69 copy(uuid[:], pool[poolPos:(poolPos+16)])
70 poolPos += 16
71 poolMu.Unlock()
72
73 uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4
74 uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10
75 return uuid, nil
76}