1.::uuid(3) Universally Unique Identifier .::uuid(3)
2
6 OSSP uuid - Universally Unique Identifier
7
9 OSSP uuid 1.6.1 (21-Feb-2008)
10
12 OSSP uuid is a ISO-C:1999 application programming interface (API) and
13 corresponding command line interface (CLI) for the generation of DCE
14 1.1, ISO/IEC 11578:1996 and RFC 4122 compliant Universally Unique
15 Identifier (UUID). It supports DCE 1.1 variant UUIDs of version 1 (time
16 and node based), version 3 (name based, MD5), version 4 (random number
17 based) and version 5 (name based, SHA-1). Additional API bindings are
18 provided for the languages ISO-C++:1998, Perl:5 and PHP:4/5. Optional
19 backward compatibility exists for the ISO-C DCE-1.1 and Perl Data::UUID
20 APIs.
21 UUIDs are 128 bit numbers which are intended to have a high likelihood
23 of uniqueness over space and time and are computationally difficult to
24 guess. They are globally unique identifiers which can be locally
25 generated without contacting a global registration authority. UUIDs are
26 intended as unique identifiers for both mass tagging objects with an
27 extremely short lifetime and to reliably identifying very persistent
28 objects across a network.
29 This is the ISO-C application programming interface (API) of OSSP uuid.
31 UUID Binary Representation
33 According to the DCE 1.1, ISO/IEC 11578:1996 and RFC 4122 standards, a
35 DCE 1.1 variant UUID is a 128 bit number defined out of 7 fields, each
36 field a multiple of an octet in size and stored in network byte order:
37 [4]
39 version
40 -->| |<--
41 | |
42 | | [16]
43 [32] [16] | |time_hi
44 time_low time_mid | _and_version
45 |<---------------------------->||<------------>||<------------>|
46 | MSB || || | |
47 | / || || | |
48 |/ || || | |
49 +------++------++------++------++------++------++------++------+~~
51 | 15 || 14 || 13 || 12 || 11 || 10 |####9 || 8 |
52 | MSO || || || || || |#### || |
53 +------++------++------++------++------++------++------++------+~~
54 7654321076543210765432107654321076543210765432107654321076543210
55 ~~+------++------++------++------++------++------++------++------+
57 ##* 7 || 6 || 5 || 4 || 3 || 2 || 1 || 0 |
58 ##* || || || || || || || LSO |
59 ~~+------++------++------++------++------++------++------++------+
60 7654321076543210765432107654321076543210765432107654321076543210
61 | | || || /|
63 | | || || / |
64 | | || || LSB |
65 |<---->||<---->||<-------------------------------------------->|
66 |clk_seq clk_seq node
67 |_hi_res _low [48]
68 |[5-6] [8]
69 | |
70 -->| |<--
71 variant
72 [2-3]
73 An example of a UUID binary representation is the octet stream 0xF8
75 0x1D 0x4F 0xAE 0x7D 0xEC 0x11 0xD0 0xA7 0x65 0x00 0xA0 0xC9 0x1E 0x6B
76 0xF6. The binary representation format is exactly what the OSSP uuid
77 API functions uuid_import() and uuid_export() deal with under
78 UUID_FMT_BIN.
79 UUID ASCII String Representation
81 According to the DCE 1.1, ISO/IEC 11578:1996 and RFC 4122 standards, a
83 DCE 1.1 variant UUID is represented as an ASCII string consisting of 8
84 hexadecimal digits followed by a hyphen, then three groups of 4
85 hexadecimal digits each followed by a hyphen, then 12 hexadecimal
86 digits. Formally, the string representation is defined by the following
87 grammar:
88 uuid = <time_low> "-"
90 <time_mid> "-"
91 <time_high_and_version> "-"
92 <clock_seq_high_and_reserved>
93 <clock_seq_low> "-"
94 <node>
95 time_low = 4*<hex_octet>
96 time_mid = 2*<hex_octet>
97 time_high_and_version = 2*<hex_octet>
98 clock_seq_high_and_reserved = <hex_octet>
99 clock_seq_low = <hex_octet>
100 node = 6*<hex_octet>
101 hex_octet = <hex_digit> <hex_digit>
102 hex_digit = "0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9"
103 |"a"|"b"|"c"|"d"|"e"|"f"
104 |"A"|"B"|"C"|"D"|"E"|"F"
105 An example of a UUID string representation is the ASCII string
107 "f81d4fae-7dec-11d0-a765-00a0c91e6bf6". The string representation
108 format is exactly what the OSSP uuid API functions uuid_import() and
109 uuid_export() deal with under UUID_FMT_STR.
110 Notice: a corresponding URL can be generated out of a ASCII string
112 representation of an UUID by prefixing with "urn:uuid:" as in
113 "urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6".
114 UUID Single Integer Value Representation
116 According to the ISO/IEC 11578:1996 and ITU-T Rec. X.667 standards, a
118 DCE 1.1 variant UUID can be also represented as a single integer value
119 consisting of a decimal number with up to 39 digits.
120 An example of a UUID single integer value representation is the decimal
122 number "329800735698586629295641978511506172918". The string
123 representation format is exactly what the OSSP uuid API functions
124 uuid_import() and uuid_export() deal with under UUID_FMT_SIV.
125 Notice: a corresponding ISO OID can be generated under the
127 "{joint-iso-itu-t(2) uuid(25)}" arc out of a single integer value
128 representation of a UUID by prefixing with "2.25.". An example OID is
129 "2.25.329800735698586629295641978511506172918". Additionally, an URL
130 can be generated by further prefixing with "urn:oid:" as in
131 "urn:oid:2.25.329800735698586629295641978511506172918".
132 UUID Variants and Versions
134 A UUID has a variant and version. The variant defines the layout of the
136 UUID. The version defines the content of the UUID. The UUID variant
137 supported in OSSP uuid is the DCE 1.1 variant only. The DCE 1.1 UUID
138 variant versions supported in OSSP uuid are:
139 Version 1 (time and node based)
141 These are the classical UUIDs, created out of a 60-bit system time,
142 a 14-bit local clock sequence and 48-bit system MAC address. The
143 MAC address can be either the real one of a physical network
144 interface card (NIC) or a random multi-cast MAC address. Version 1
145 UUIDs are usually used as one-time global unique identifiers.
146 Version 3 (name based, MD5)
148 These are UUIDs which are based on the 128-bit MD5 message digest
149 of the concatenation of a 128-bit namespace UUID and a name string
150 of arbitrary length. Version 3 UUIDs are usually used for non-
151 unique but repeatable message digest identifiers.
152 Version 4 (random data based)
154 These are UUIDs which are based on just 128-bit of random data.
155 Version 4 UUIDs are usually used as one-time local unique
156 identifiers.
157 Version 5 (name based, SHA-1)
159 These are UUIDs which are based on the 160-bit SHA-1 message digest
160 of the concatenation of a 128-bit namespace UUID and a name string
161 of arbitrary length. Version 5 UUIDs are usually used for non-
162 unique but repeatable message digest identifiers.
163 UUID Uniqueness
165 Version 1 UUIDs are guaranteed to be unique through combinations of
167 hardware addresses, time stamps and random seeds. There is a reference
168 in the UUID to the hardware (MAC) address of the first network
169 interface card (NIC) on the host which generated the UUID -- this
170 reference is intended to ensure the UUID will be unique in space as the
171 MAC address of every network card is assigned by a single global
172 authority (IEEE) and is guaranteed to be unique. The next component in
173 a UUID is a timestamp which, as clock always (should) move forward,
174 will be unique in time. Just in case some part of the above goes wrong
175 (the hardware address cannot be determined or the clock moved steps
176 backward), there is a random clock sequence component placed into the
177 UUID as a "catch-all" for uniqueness.
178 Version 3 and version 5 UUIDs are guaranteed to be inherently globally
180 unique if the combination of namespace and name used to generate them
181 is unique.
182 Version 4 UUIDs are not guaranteed to be globally unique, because they
184 are generated out of locally gathered pseudo-random numbers only.
185 Nevertheless there is still a high likelihood of uniqueness over space
186 and time and that they are computationally difficult to guess.
187 Nil UUID
189 There is a special Nil UUID consisting of all octets set to zero in the
191 binary representation. It can be used as a special UUID value which
192 does not conflict with real UUIDs.
193
195 The ISO-C Application Programming Interface (API) of OSSP uuid consists
196 of the following components.
197 CONSTANTS
199 The following constants are provided:
201 UUID_VERSION
203 The hexadecimal encoded OSSP uuid version. This allows compile-time
204 checking of the OSSP uuid version. For run-time checking use
205 uuid_version() instead.
206 The hexadecimal encoding for a version "$v.$r$t$l" is calculated
208 with the GNU shtool version command and is (in Perl-style for
209 concise description) "sprintf('0x%x%02x%d%02x', $v, $r, {qw(s 9 . 2
210 b 1 a 0)}->{$t}, ($t eq 's' ? 99 : $l))", i.e., the version 0.9.6
211 is encoded as "0x009206".
212 UUID_LEN_BIN, UUID_LEN_STR, UUID_LEN_SIV
214 The number of octets of the UUID binary and string representations.
215 Notice that the lengths of the string representation (UUID_LEN_STR)
216 and the lengths of the single integer value representation
217 (UUID_LEN_SIV) does not include the necessary NUL termination
218 character.
219 UUID_MAKE_V1, UUID_MAKE_V3, UUID_MAKE_V4, UUID_MAKE_V5, UUID_MAKE_MC
221 The mode bits for use with uuid_make(). The UUID_MAKE_VN specify
222 which UUID version to generate. The UUID_MAKE_MC forces the use of
223 a random multi-cast MAC address instead of the real physical MAC
224 address in version 1 UUIDs.
225 UUID_RC_OK, UUID_RC_ARG, UUID_RC_MEM, UUID_RC_SYS, UUID_RC_INT,
227 UUID_RC_IMP
228 The possible numerical return-codes of API functions. The
229 UUID_RC_OK indicates success, the others indicate errors. Use
230 uuid_error() to translate them into string versions.
231 UUID_FMT_BIN, UUID_FMT_STR, UUID_FMT_SIV, UUID_FMT_TXT
233 The fmt formats for use with uuid_import() and uuid_export(). The
234 UUID_FMT_BIN indicates the UUID binary representation (of length
235 UUID_LEN_BIN), the UUID_FMT_STR indicates the UUID string
236 representation (of length UUID_LEN_STR), the UUID_FMT_SIV indicates
237 the UUID single integer value representation (of maximum length
238 UUID_LEN_SIV) and the UUID_FMT_TXT indicates the textual
239 description (of arbitrary length) of a UUID.
240 FUNCTIONS
242 The following functions are provided:
244 uuid_rc_t uuid_create(uuid_t **uuid);
246 Create a new UUID object and store a pointer to it in *uuid. A
247 UUID object consists of an internal representation of a UUID, the
248 internal PRNG and MD5 generator contexts, and cached MAC address
249 and timestamp information. The initial UUID is the Nil UUID.
250 uuid_rc_t uuid_destroy(uuid_t *uuid);
252 Destroy UUID object uuid.
253 uuid_rc_t uuid_clone(const uuid_t *uuid, uuid_t **uuid_clone);
255 Clone UUID object uuid and store new UUID object in uuid_clone.
256 uuid_rc_t uuid_isnil(const uuid_t *uuid, int *result);
258 Checks whether the UUID in uuid is the Nil UUID. If this is the
259 case, it returns true in *result. Else it returns false in
260 *result.
261 uuid_rc_t uuid_compare(const uuid_t *uuid, const uuid_t *uuid2, int
263 *result);
264 Compares the order of the two UUIDs in uuid1 and uuid2 and returns
265 the result in *result: -1 if uuid1 is smaller than uuid2, 0 if
266 uuid1 is equal to uuid2 and +1 if uuid1 is greater than uuid2.
267 uuid_rc_t uuid_import(uuid_t *uuid, uuid_fmt_t fmt, const void
269 *data_ptr, size_t data_len);
270 Imports a UUID uuid from an external representation of format fmt.
271 The data is read from the buffer at data_ptr which contains at
272 least data_len bytes.
273 The format of the external representation is specified by fmt and
275 the minimum expected length in data_len depends on it. Valid values
276 for fmt are UUID_FMT_BIN, UUID_FMT_STR and UUID_FMT_SIV.
277 uuid_rc_t uuid_export(const uuid_t *uuid, uuid_fmt_t fmt, void
279 *data_ptr, size_t *data_len);
280 Exports a UUID uuid into an external representation of format fmt.
281 Valid values for fmt are UUID_FMT_BIN, UUID_FMT_STR, UUID_FMT_SIV
282 and UUID_FMT_TXT.
283 The data is written to the buffer whose location is obtained by
285 dereferencing data_ptr after a "cast" to the appropriate pointer-
286 to-pointer type. Hence the generic pointer argument data_ptr is
287 expected to be a pointer to a "pointer of a particular type", i.e.,
288 it has to be of type "unsigned char **" for UUID_FMT_BIN and "char
289 **" for UUID_FMT_STR, UUID_FMT_SIV and UUID_FMT_TXT.
290 The buffer has to be room for at least *data_len bytes. If the
292 value of the pointer after "casting" and dereferencing data_ptr is
293 NULL, data_len is ignored as input and a new buffer is allocated
294 and returned in the pointer after "casting" and dereferencing
295 data_ptr (the caller has to free(3) it later on).
296 If data_len is not NULL, the number of available bytes in the
298 buffer has to be provided in *data_len and the number of actually
299 written bytes are returned in *data_len again. The minimum required
300 buffer length depends on the external representation as specified
301 by fmt and is at least UUID_LEN_BIN for UUID_FMT_BIN, UUID_LEN_STR
302 for UUID_FMT_STR and UUID_LEN_SIV for UUID_FMT_SIV. For
303 UUID_FMT_TXT a buffer of unspecified length is required and hence
304 it is recommended to allow OSSP uuid to allocate the buffer as
305 necessary.
306 uuid_rc_t uuid_load(uuid_t *uuid, const char *name);
308 Loads a pre-defined UUID value into the UUID object uuid. The
309 following name arguments are currently known:
310 name UUID
312 nil 00000000-0000-0000-0000-000000000000
313 ns:DNS 6ba7b810-9dad-11d1-80b4-00c04fd430c8
314 ns:URL 6ba7b811-9dad-11d1-80b4-00c04fd430c8
315 ns:OID 6ba7b812-9dad-11d1-80b4-00c04fd430c8
316 ns:X500 6ba7b814-9dad-11d1-80b4-00c04fd430c8
317 The "ns:XXX" are names of pre-defined name-space UUIDs for use in
319 the generation of DCE 1.1 version 3 and version 5 UUIDs.
320 uuid_rc_t uuid_make(uuid_t *uuid, unsigned int mode, ...);
322 Generates a new UUID in uuid according to mode and optional
323 arguments (dependent on mode).
324 If mode contains the UUID_MAKE_V1 bit, a DCE 1.1 variant UUID of
326 version 1 is generated. Then optionally the bit UUID_MAKE_MC forces
327 the use of random multi-cast MAC address instead of the real
328 physical MAC address (the default). The UUID is generated out of
329 the 60-bit current system time, a 12-bit clock sequence and the
330 48-bit MAC address.
331 If mode contains the UUID_MAKE_V3 or UUID_MAKE_V5 bit, a DCE 1.1
333 variant UUID of version 3 or 5 is generated and two additional
334 arguments are expected: first, a namespace UUID object (uuid_t *).
335 Second, a name string of arbitrary length (const char *). The UUID
336 is generated out of the 128-bit MD5 or 160-bit SHA-1 from the
337 concatenated octet stream of namespace UUID and name string.
338 If mode contains the UUID_MAKE_V4 bit, a DCE 1.1 variant UUID of
340 version 4 is generated. The UUID is generated out of 128-bit random
341 data.
342 char *uuid_error(uuid_rc_t rc);
344 Returns a constant string representation corresponding to the
345 return-code rc for use in displaying OSSP uuid errors.
346 unsigned long uuid_version(void);
348 Returns the hexadecimal encoded OSSP uuid version as compiled into
349 the library object files. This allows run-time checking of the OSSP
350 uuid version. For compile-time checking use UUID_VERSION instead.
351
353 The following shows an example usage of the API. Error handling is
354 omitted for code simplification and has to be re-added for production
355 code.
356 /* generate a DCE 1.1 v1 UUID from system environment */
358 char *uuid_v1(void)
359 {
360 uuid_t *uuid;
361 char *str;
362 uuid_create(&uuid);
364 uuid_make(uuid, UUID_MAKE_V1);
365 str = NULL;
366 uuid_export(uuid, UUID_FMT_STR, &str, NULL);
367 uuid_destroy(uuid);
368 return str;
369 }
370 /* generate a DCE 1.1 v3 UUID from an URL */
372 char *uuid_v3(const char *url)
373 {
374 uuid_t *uuid;
375 uuid_t *uuid_ns;
376 char *str;
377 uuid_create(&uuid);
379 uuid_create(&uuid_ns);
380 uuid_load(uuid_ns, "ns:URL");
381 uuid_make(uuid, UUID_MAKE_V3, uuid_ns, url);
382 str = NULL;
383 uuid_export(uuid, UUID_FMT_STR, &str, NULL);
384 uuid_destroy(uuid_ns);
385 uuid_destroy(uuid);
386 return str;
387 }
388
390 The following are references to UUID documentation and specifications:
391 · A Universally Unique IDentifier (UUID) URN Namespace, P. Leach, M.
393 Mealling, R. Salz, IETF RFC 4122, July 2005, 32 pages,
394 http://www.ietf.org/rfc/rfc4122.txt
395 · Information Technology -- Open Systems Interconnection (OSI),
397 Procedures for the operation of OSI Registration Authorities:
398 Generation and Registration of Universally Unique Identifiers
399 (UUIDs) and their Use as ASN.1 Object Identifier Components,
400 ISO/IEC 9834-8:2004 / ITU-T Rec. X.667, 2004, December 2004, 25
401 pages, http://www.itu.int/ITU-T/studygroups/com17/oid/X.667-E.pdf
402 · DCE 1.1: Remote Procedure Call, appendix Universally Unique
404 Identifier, Open Group Technical Standard Document Number C706,
405 August 1997, 737 pages, (supersedes C309 DCE: Remote Procedure Call
406 8/1994, which was basis for ISO/IEC 11578:1996 specification),
407 http://www.opengroup.org/publications/catalog/c706.htm
408 · Information technology -- Open Systems Interconnection (OSI),
410 Remote Procedure Call (RPC), ISO/IEC 11578:1996, August 2001, 570
411 pages, (CHF 340,00), http://www.iso.ch/cate/d2229.html
412 · HTTP Extensions for Distributed Authoring (WebDAV), section 6.4.1
414 Node Field Generation Without the IEEE 802 Address, IETF Request
415 for Comments: RFC 2518, February 1999, 94 pages,
416 http://www.ietf.org/rfc/rfc2518.txt
417 · DCE 1.1 compliant UUID functions, FreeBSD manual pages uuid(3) and
419 uuidgen(2),
420 http://www.freebsd.org/cgi/man.cgi?query=uuid&manpath=FreeBSD+6.0-RELEASE
421
423 OSSP uuid was implemented in January 2004 by Ralf S. Engelschall
424 <rse@engelschall.com>. It was prompted by the use of UUIDs in the OSSP
425 as and OpenPKG projects. It is a clean room implementation intended to
426 be strictly standards compliant and maximum portable.
427
429 uuid(1), uuid-config(1), OSSP::uuid(3).
43021-Feb-2008 OSSP uuid 1.6.1 .::uuid(3)