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Scott Baker2d897982019-09-24 11:50:08 -07001// Copyright 2018 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 (
8 "bytes"
9 "crypto/rand"
10 "encoding/hex"
11 "errors"
12 "fmt"
13 "io"
14 "strings"
15)
16
17// A UUID is a 128 bit (16 byte) Universal Unique IDentifier as defined in RFC
18// 4122.
19type UUID [16]byte
20
21// A Version represents a UUID's version.
22type Version byte
23
24// A Variant represents a UUID's variant.
25type Variant byte
26
27// Constants returned by Variant.
28const (
29 Invalid = Variant(iota) // Invalid UUID
30 RFC4122 // The variant specified in RFC4122
31 Reserved // Reserved, NCS backward compatibility.
32 Microsoft // Reserved, Microsoft Corporation backward compatibility.
33 Future // Reserved for future definition.
34)
35
36var rander = rand.Reader // random function
37
38// Parse decodes s into a UUID or returns an error. Both the standard UUID
39// forms of xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx and
40// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx are decoded as well as the
41// Microsoft encoding {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} and the raw hex
42// encoding: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.
43func Parse(s string) (UUID, error) {
44 var uuid UUID
45 switch len(s) {
46 // xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
47 case 36:
48
49 // urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
50 case 36 + 9:
51 if strings.ToLower(s[:9]) != "urn:uuid:" {
52 return uuid, fmt.Errorf("invalid urn prefix: %q", s[:9])
53 }
54 s = s[9:]
55
56 // {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
57 case 36 + 2:
58 s = s[1:]
59
60 // xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
61 case 32:
62 var ok bool
63 for i := range uuid {
64 uuid[i], ok = xtob(s[i*2], s[i*2+1])
65 if !ok {
66 return uuid, errors.New("invalid UUID format")
67 }
68 }
69 return uuid, nil
70 default:
71 return uuid, fmt.Errorf("invalid UUID length: %d", len(s))
72 }
73 // s is now at least 36 bytes long
74 // it must be of the form xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
75 if s[8] != '-' || s[13] != '-' || s[18] != '-' || s[23] != '-' {
76 return uuid, errors.New("invalid UUID format")
77 }
78 for i, x := range [16]int{
79 0, 2, 4, 6,
80 9, 11,
81 14, 16,
82 19, 21,
83 24, 26, 28, 30, 32, 34} {
84 v, ok := xtob(s[x], s[x+1])
85 if !ok {
86 return uuid, errors.New("invalid UUID format")
87 }
88 uuid[i] = v
89 }
90 return uuid, nil
91}
92
93// ParseBytes is like Parse, except it parses a byte slice instead of a string.
94func ParseBytes(b []byte) (UUID, error) {
95 var uuid UUID
96 switch len(b) {
97 case 36: // xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
98 case 36 + 9: // urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
99 if !bytes.Equal(bytes.ToLower(b[:9]), []byte("urn:uuid:")) {
100 return uuid, fmt.Errorf("invalid urn prefix: %q", b[:9])
101 }
102 b = b[9:]
103 case 36 + 2: // {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
104 b = b[1:]
105 case 32: // xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
106 var ok bool
107 for i := 0; i < 32; i += 2 {
108 uuid[i/2], ok = xtob(b[i], b[i+1])
109 if !ok {
110 return uuid, errors.New("invalid UUID format")
111 }
112 }
113 return uuid, nil
114 default:
115 return uuid, fmt.Errorf("invalid UUID length: %d", len(b))
116 }
117 // s is now at least 36 bytes long
118 // it must be of the form xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
119 if b[8] != '-' || b[13] != '-' || b[18] != '-' || b[23] != '-' {
120 return uuid, errors.New("invalid UUID format")
121 }
122 for i, x := range [16]int{
123 0, 2, 4, 6,
124 9, 11,
125 14, 16,
126 19, 21,
127 24, 26, 28, 30, 32, 34} {
128 v, ok := xtob(b[x], b[x+1])
129 if !ok {
130 return uuid, errors.New("invalid UUID format")
131 }
132 uuid[i] = v
133 }
134 return uuid, nil
135}
136
137// MustParse is like Parse but panics if the string cannot be parsed.
138// It simplifies safe initialization of global variables holding compiled UUIDs.
139func MustParse(s string) UUID {
140 uuid, err := Parse(s)
141 if err != nil {
142 panic(`uuid: Parse(` + s + `): ` + err.Error())
143 }
144 return uuid
145}
146
147// FromBytes creates a new UUID from a byte slice. Returns an error if the slice
148// does not have a length of 16. The bytes are copied from the slice.
149func FromBytes(b []byte) (uuid UUID, err error) {
150 err = uuid.UnmarshalBinary(b)
151 return uuid, err
152}
153
154// Must returns uuid if err is nil and panics otherwise.
155func Must(uuid UUID, err error) UUID {
156 if err != nil {
157 panic(err)
158 }
159 return uuid
160}
161
162// String returns the string form of uuid, xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
163// , or "" if uuid is invalid.
164func (uuid UUID) String() string {
165 var buf [36]byte
166 encodeHex(buf[:], uuid)
167 return string(buf[:])
168}
169
170// URN returns the RFC 2141 URN form of uuid,
171// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx, or "" if uuid is invalid.
172func (uuid UUID) URN() string {
173 var buf [36 + 9]byte
174 copy(buf[:], "urn:uuid:")
175 encodeHex(buf[9:], uuid)
176 return string(buf[:])
177}
178
179func encodeHex(dst []byte, uuid UUID) {
180 hex.Encode(dst, uuid[:4])
181 dst[8] = '-'
182 hex.Encode(dst[9:13], uuid[4:6])
183 dst[13] = '-'
184 hex.Encode(dst[14:18], uuid[6:8])
185 dst[18] = '-'
186 hex.Encode(dst[19:23], uuid[8:10])
187 dst[23] = '-'
188 hex.Encode(dst[24:], uuid[10:])
189}
190
191// Variant returns the variant encoded in uuid.
192func (uuid UUID) Variant() Variant {
193 switch {
194 case (uuid[8] & 0xc0) == 0x80:
195 return RFC4122
196 case (uuid[8] & 0xe0) == 0xc0:
197 return Microsoft
198 case (uuid[8] & 0xe0) == 0xe0:
199 return Future
200 default:
201 return Reserved
202 }
203}
204
205// Version returns the version of uuid.
206func (uuid UUID) Version() Version {
207 return Version(uuid[6] >> 4)
208}
209
210func (v Version) String() string {
211 if v > 15 {
212 return fmt.Sprintf("BAD_VERSION_%d", v)
213 }
214 return fmt.Sprintf("VERSION_%d", v)
215}
216
217func (v Variant) String() string {
218 switch v {
219 case RFC4122:
220 return "RFC4122"
221 case Reserved:
222 return "Reserved"
223 case Microsoft:
224 return "Microsoft"
225 case Future:
226 return "Future"
227 case Invalid:
228 return "Invalid"
229 }
230 return fmt.Sprintf("BadVariant%d", int(v))
231}
232
233// SetRand sets the random number generator to r, which implements io.Reader.
234// If r.Read returns an error when the package requests random data then
235// a panic will be issued.
236//
237// Calling SetRand with nil sets the random number generator to the default
238// generator.
239func SetRand(r io.Reader) {
240 if r == nil {
241 rander = rand.Reader
242 return
243 }
244 rander = r
245}