1// 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 "sync"
16)
17
18// A UUID is a 128 bit (16 byte) Universal Unique IDentifier as defined in RFC
19// 4122.
20type UUID [16]byte
21
22// A Version represents a UUID's version.
23type Version byte
24
25// A Variant represents a UUID's variant.
26type Variant byte
27
28// Constants returned by Variant.
29const (
30 Invalid = Variant(iota) // Invalid UUID
31 RFC4122 // The variant specified in RFC4122
32 Reserved // Reserved, NCS backward compatibility.
33 Microsoft // Reserved, Microsoft Corporation backward compatibility.
34 Future // Reserved for future definition.
35)
36
37const randPoolSize = 16 * 16
38
39var (
40 rander = rand.Reader // random function
41 poolEnabled = false
42 poolMu sync.Mutex
43 poolPos = randPoolSize // protected with poolMu
44 pool [randPoolSize]byte // protected with poolMu
45)
46
47type invalidLengthError struct{ len int }
48
49func (err invalidLengthError) Error() string {
50 return fmt.Sprintf("invalid UUID length: %d", err.len)
51}
52
53// IsInvalidLengthError is matcher function for custom error invalidLengthError
54func IsInvalidLengthError(err error) bool {
55 _, ok := err.(invalidLengthError)
56 return ok
57}
58
59// Parse decodes s into a UUID or returns an error if it cannot be parsed. Both
60// the standard UUID forms defined in RFC 4122
61// (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx and
62// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx) are decoded. In addition,
63// Parse accepts non-standard strings such as the raw hex encoding
64// xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx and 38 byte "Microsoft style" encodings,
65// e.g. {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}. Only the middle 36 bytes are
66// examined in the latter case. Parse should not be used to validate strings as
67// it parses non-standard encodings as indicated above.
68func Parse(s string) (UUID, error) {
69 var uuid UUID
70 switch len(s) {
71 // xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
72 case 36:
73
74 // urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
75 case 36 + 9:
76 if !strings.EqualFold(s[:9], "urn:uuid:") {
77 return uuid, fmt.Errorf("invalid urn prefix: %q", s[:9])
78 }
79 s = s[9:]
80
81 // {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
82 case 36 + 2:
83 s = s[1:]
84
85 // xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
86 case 32:
87 var ok bool
88 for i := range uuid {
89 uuid[i], ok = xtob(s[i*2], s[i*2+1])
90 if !ok {
91 return uuid, errors.New("invalid UUID format")
92 }
93 }
94 return uuid, nil
95 default:
96 return uuid, invalidLengthError{len(s)}
97 }
98 // s is now at least 36 bytes long
99 // it must be of the form xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
100 if s[8] != '-' || s[13] != '-' || s[18] != '-' || s[23] != '-' {
101 return uuid, errors.New("invalid UUID format")
102 }
103 for i, x := range [16]int{
104 0, 2, 4, 6,
105 9, 11,
106 14, 16,
107 19, 21,
108 24, 26, 28, 30, 32, 34,
109 } {
110 v, ok := xtob(s[x], s[x+1])
111 if !ok {
112 return uuid, errors.New("invalid UUID format")
113 }
114 uuid[i] = v
115 }
116 return uuid, nil
117}
118
119// ParseBytes is like Parse, except it parses a byte slice instead of a string.
120func ParseBytes(b []byte) (UUID, error) {
121 var uuid UUID
122 switch len(b) {
123 case 36: // xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
124 case 36 + 9: // urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
125 if !bytes.EqualFold(b[:9], []byte("urn:uuid:")) {
126 return uuid, fmt.Errorf("invalid urn prefix: %q", b[:9])
127 }
128 b = b[9:]
129 case 36 + 2: // {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
130 b = b[1:]
131 case 32: // xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
132 var ok bool
133 for i := 0; i < 32; i += 2 {
134 uuid[i/2], ok = xtob(b[i], b[i+1])
135 if !ok {
136 return uuid, errors.New("invalid UUID format")
137 }
138 }
139 return uuid, nil
140 default:
141 return uuid, invalidLengthError{len(b)}
142 }
143 // s is now at least 36 bytes long
144 // it must be of the form xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
145 if b[8] != '-' || b[13] != '-' || b[18] != '-' || b[23] != '-' {
146 return uuid, errors.New("invalid UUID format")
147 }
148 for i, x := range [16]int{
149 0, 2, 4, 6,
150 9, 11,
151 14, 16,
152 19, 21,
153 24, 26, 28, 30, 32, 34,
154 } {
155 v, ok := xtob(b[x], b[x+1])
156 if !ok {
157 return uuid, errors.New("invalid UUID format")
158 }
159 uuid[i] = v
160 }
161 return uuid, nil
162}
163
164// MustParse is like Parse but panics if the string cannot be parsed.
165// It simplifies safe initialization of global variables holding compiled UUIDs.
166func MustParse(s string) UUID {
167 uuid, err := Parse(s)
168 if err != nil {
169 panic(`uuid: Parse(` + s + `): ` + err.Error())
170 }
171 return uuid
172}
173
174// FromBytes creates a new UUID from a byte slice. Returns an error if the slice
175// does not have a length of 16. The bytes are copied from the slice.
176func FromBytes(b []byte) (uuid UUID, err error) {
177 err = uuid.UnmarshalBinary(b)
178 return uuid, err
179}
180
181// Must returns uuid if err is nil and panics otherwise.
182func Must(uuid UUID, err error) UUID {
183 if err != nil {
184 panic(err)
185 }
186 return uuid
187}
188
189// Validate returns an error if s is not a properly formatted UUID in one of the following formats:
190// xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
191// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
192// xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
193// {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
194// It returns an error if the format is invalid, otherwise nil.
195func Validate(s string) error {
196 switch len(s) {
197 // Standard UUID format
198 case 36:
199
200 // UUID with "urn:uuid:" prefix
201 case 36 + 9:
202 if !strings.EqualFold(s[:9], "urn:uuid:") {
203 return fmt.Errorf("invalid urn prefix: %q", s[:9])
204 }
205 s = s[9:]
206
207 // UUID enclosed in braces
208 case 36 + 2:
209 if s[0] != '{' || s[len(s)-1] != '}' {
210 return fmt.Errorf("invalid bracketed UUID format")
211 }
212 s = s[1 : len(s)-1]
213
214 // UUID without hyphens
215 case 32:
216 for i := 0; i < len(s); i += 2 {
217 _, ok := xtob(s[i], s[i+1])
218 if !ok {
219 return errors.New("invalid UUID format")
220 }
221 }
222
223 default:
224 return invalidLengthError{len(s)}
225 }
226
227 // Check for standard UUID format
228 if len(s) == 36 {
229 if s[8] != '-' || s[13] != '-' || s[18] != '-' || s[23] != '-' {
230 return errors.New("invalid UUID format")
231 }
232 for _, x := range []int{0, 2, 4, 6, 9, 11, 14, 16, 19, 21, 24, 26, 28, 30, 32, 34} {
233 if _, ok := xtob(s[x], s[x+1]); !ok {
234 return errors.New("invalid UUID format")
235 }
236 }
237 }
238
239 return nil
240}
241
242// String returns the string form of uuid, xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
243// , or "" if uuid is invalid.
244func (uuid UUID) String() string {
245 var buf [36]byte
246 encodeHex(buf[:], uuid)
247 return string(buf[:])
248}
249
250// URN returns the RFC 2141 URN form of uuid,
251// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx, or "" if uuid is invalid.
252func (uuid UUID) URN() string {
253 var buf [36 + 9]byte
254 copy(buf[:], "urn:uuid:")
255 encodeHex(buf[9:], uuid)
256 return string(buf[:])
257}
258
259func encodeHex(dst []byte, uuid UUID) {
260 hex.Encode(dst, uuid[:4])
261 dst[8] = '-'
262 hex.Encode(dst[9:13], uuid[4:6])
263 dst[13] = '-'
264 hex.Encode(dst[14:18], uuid[6:8])
265 dst[18] = '-'
266 hex.Encode(dst[19:23], uuid[8:10])
267 dst[23] = '-'
268 hex.Encode(dst[24:], uuid[10:])
269}
270
271// Variant returns the variant encoded in uuid.
272func (uuid UUID) Variant() Variant {
273 switch {
274 case (uuid[8] & 0xc0) == 0x80:
275 return RFC4122
276 case (uuid[8] & 0xe0) == 0xc0:
277 return Microsoft
278 case (uuid[8] & 0xe0) == 0xe0:
279 return Future
280 default:
281 return Reserved
282 }
283}
284
285// Version returns the version of uuid.
286func (uuid UUID) Version() Version {
287 return Version(uuid[6] >> 4)
288}
289
290func (v Version) String() string {
291 if v > 15 {
292 return fmt.Sprintf("BAD_VERSION_%d", v)
293 }
294 return fmt.Sprintf("VERSION_%d", v)
295}
296
297func (v Variant) String() string {
298 switch v {
299 case RFC4122:
300 return "RFC4122"
301 case Reserved:
302 return "Reserved"
303 case Microsoft:
304 return "Microsoft"
305 case Future:
306 return "Future"
307 case Invalid:
308 return "Invalid"
309 }
310 return fmt.Sprintf("BadVariant%d", int(v))
311}
312
313// SetRand sets the random number generator to r, which implements io.Reader.
314// If r.Read returns an error when the package requests random data then
315// a panic will be issued.
316//
317// Calling SetRand with nil sets the random number generator to the default
318// generator.
319func SetRand(r io.Reader) {
320 if r == nil {
321 rander = rand.Reader
322 return
323 }
324 rander = r
325}
326
327// EnableRandPool enables internal randomness pool used for Random
328// (Version 4) UUID generation. The pool contains random bytes read from
329// the random number generator on demand in batches. Enabling the pool
330// may improve the UUID generation throughput significantly.
331//
332// Since the pool is stored on the Go heap, this feature may be a bad fit
333// for security sensitive applications.
334//
335// Both EnableRandPool and DisableRandPool are not thread-safe and should
336// only be called when there is no possibility that New or any other
337// UUID Version 4 generation function will be called concurrently.
338func EnableRandPool() {
339 poolEnabled = true
340}
341
342// DisableRandPool disables the randomness pool if it was previously
343// enabled with EnableRandPool.
344//
345// Both EnableRandPool and DisableRandPool are not thread-safe and should
346// only be called when there is no possibility that New or any other
347// UUID Version 4 generation function will be called concurrently.
348func DisableRandPool() {
349 poolEnabled = false
350 defer poolMu.Unlock()
351 poolMu.Lock()
352 poolPos = randPoolSize
353}
354
355// UUIDs is a slice of UUID types.
356type UUIDs []UUID
357
358// Strings returns a string slice containing the string form of each UUID in uuids.
359func (uuids UUIDs) Strings() []string {
360 var uuidStrs = make([]string, len(uuids))
361 for i, uuid := range uuids {
362 uuidStrs[i] = uuid.String()
363 }
364 return uuidStrs
365}