uuid

This library implements a Universally Unique Identifier (UUID) generator. Currently version 1, version 3, version 4, version 5, and version 7 UUIDs are supported. Version 5 support requires a Prolog backend with support for unbounded integer arithmetic. For reference material, see e.g.

https://en.wikipedia.org/wiki/Universally_unique_identifier

Some backends provide time stamps with low granularity (e.g., seconds but not milliseconds or nanoseconds). To compensate, the generation of version 1 UUIDs uses 14 random bits for the clock sequence.

Some backends only provide access to local time. On those backends, the uuid_v1/2 and uuid_v7/1 predicates preserve the backend behavior and use the available local time fields when computing the UUID timestamp. To compute UUID timestamps using UTC instead, use the uuid_v1/3 and uuid_v7/2 predicates and pass the current local UTC offset as Z, +HH:MM, or -HH:MM.

The generation of version 4 and version 7 UUIDs uses the /dev/urandom random number generator when available. This includes macOS, Linux, *BSD, and other POSIX operating-systems. On Windows, a pseudo-random generator is used, but randomized using the current wall time.

Version 3 and version 5 UUIDs are namespace-name based UUIDs using the MD5 and SHA-1 hash functions, respectively.

Version 7 UUIDs are time-ordered using a Unix Epoch timestamp in milliseconds, as specified in RFC 9562. They are recommended over version 1 UUIDs for new applications due to improved entropy and sortability characteristics.

UUIDs can be generated as atoms, lists of characters, or lists of character codes.

See also the cuid2, ksuid, ids, nanoid, snowflakeid, and ulid libraries.

API documentation

Open the ../../apis/library_index.html#uuid link in a web browser.

Loading

To load all entities in this library, load the loader.lgt file:

| ?- logtalk_load(uuid(loader)).

Testing

To test this library predicates, load the tester.lgt file:

| ?- logtalk_load(uuid(tester)).

Generating version 1 UUIDs

By default, version 1 UUIDs are generated as atoms. For example:

| ?- uuid::uuid_v1([0xf2,0xd1,0x90,0x94,0xdc,0x4b], UUID).
UUID = '00a66fc0-82cf-11eb-bc83-f2d19094dc4b'
yes

To generate a UUID using a list of characters representation, use instead the uuid/1 parametric object:

| ?- uuid(chars)::uuid_v1([0xf2,0xd1,0x90,0x94,0xdc,0x4b], UUID).
UUID = ['0','0',d,e,'9','0',c,'0',-,'8','2',c,f,-,'1','1',e,b,-,
        a,'9','8','5',-,f,'2',d,'1','9','0','9','4',d,c,'4',b]
yes

Similarly, to get a UUID using a list of character codes representation:

| ?- uuid(codes)::uuid_v1([0xf2,0xd1,0x90,0x94,0xdc,0x4b], UUID).
UUID = [48,48,52,99,99,54,99,48,45,56,50,99,102,45,49,49,101,98,45,
        98,57,102,52,45,102,50,100,49,57,48,57,52,100,99,52,98]
yes

When the backend only provides access to local time, use uuid_v1/3 with the current local UTC offset to compute the UUID timestamp using UTC:

| ?- uuid::uuid_v1([0xf2,0xd1,0x90,0x94,0xdc,0x4b], '+01:00', UUID).
UUID = '00a66fc0-82cf-11eb-bc83-f2d19094dc4b'
yes

Generating version 4 UUIDs

By default, version 4 UUIDs are generated as atoms. For example:

| ?- uuid::uuid_v4(UUID).
UUID = '1c652782-69c5-4252-88c8-09e576a44db5'
yes

To generate a UUID using a list of characters representation, use instead the uuid/1 parametric object:

| ?- uuid(chars)::uuid_v4(UUID).
UUID = [d,'3',d,'3','3','5','1','3',-,'8','1',e,c,-,'4',d,'2','6',-,
        '9',f,'2','2',-,e,d,'9','5',e,'0','0',e,'1','5','7','0']
yes

Similar to get a UUID using a list of character codes representation:

| ?- uuid(codes)::uuid_v4(UUID).
UUID = [102,97,52,54,57,98,100,50,45,51,57,54,51,45,52,97,100,55,45,
        98,50,50,55,45,101,100,52,99,56,55,99,54,53,55,102,98]
yes

Generating version 3 UUIDs

Version 3 UUIDs are namespace-name based UUIDs using the MD5 hash function. For example:

| ?- uuid::uuid_v3('6ba7b810-9dad-11d1-80b4-00c04fd430c8', 'www.widgets.com', UUID).
UUID = '3d813cbb-47fb-32ba-91df-831e1593ac29'
yes

To generate a UUID using a list of characters representation, use instead the uuid/1 parametric object:

| ?- uuid(chars)::uuid_v3('6ba7b810-9dad-11d1-80b4-00c04fd430c8', 'www.widgets.com', UUID).
UUID = ['3',d,'8','1','3',c,b,b,-,'4','7',f,b,-,'3','2',b,a,-,
        '9','1',d,f,-,'8','3','1',e,'1','5','9','3',a,c,'2','9']
yes

Similarly, to get a UUID using a list of character codes representation:

| ?- uuid(codes)::uuid_v3('6ba7b810-9dad-11d1-80b4-00c04fd430c8', 'www.widgets.com', UUID).
UUID = [51,100,56,49,51,99,98,98,45,52,55,102,98,45,51,50,98,97,45,
        57,49,100,102,45,56,51,49,101,49,53,57,51,97,99,50,57]
yes

Generating version 5 UUIDs

Version 5 UUIDs are namespace-name based UUIDs using the SHA-1 hash function. This predicate is only available on Prolog backends with support for unbounded integer arithmetic. For example:

| ?- uuid::uuid_v5('6ba7b810-9dad-11d1-80b4-00c04fd430c8', 'www.widgets.com', UUID).
UUID = '21f7f8de-8051-5b89-8680-0195ef798b6a'
yes

To generate a UUID using a list of characters representation, use instead the uuid/1 parametric object:

| ?- uuid(chars)::uuid_v5('6ba7b810-9dad-11d1-80b4-00c04fd430c8', 'www.widgets.com', UUID).
UUID = ['2','1',f,'7',f,'8',d,e,-,'8','0','5','1',-,'5',b,'8','9',-,
        '8','6','8','0',-,'0','1','9','5',e,f,'7','9','8',b,'6',a]
yes

Similarly, to get a UUID using a list of character codes representation:

| ?- uuid(codes)::uuid_v5('6ba7b810-9dad-11d1-80b4-00c04fd430c8', 'www.widgets.com', UUID).
UUID = [50,49,102,55,102,56,100,101,45,56,48,53,49,45,53,98,56,57,45,
        56,54,56,48,45,48,49,57,53,101,102,55,57,56,98,54,97]
yes

Generating version 7 UUIDs

Version 7 UUIDs are time-ordered using the Unix Epoch timestamp in milliseconds (as specified in RFC 9562). By default, version 7 UUIDs are generated as atoms. For example:

| ?- uuid::uuid_v7(UUID).
UUID = '018d5f3c-9b5a-7c4e-8f2a-1b3c4d5e6f70'
yes

To generate a UUID using a list of characters representation, use instead the uuid/1 parametric object:

| ?- uuid(chars)::uuid_v7(UUID).
UUID = ['0','1','8',d,'5',f,'3',c,-,'9',b,'5',a,-,'7',c,'4',e,-,
        '8',f,'2',a,-,'1',b,'3',c,'4',d,'5',e,'6',f,'7','0']
yes

Similar to get a UUID using a list of character codes representation:

| ?- uuid(codes)::uuid_v7(UUID).
UUID = [48,49,56,100,53,102,51,99,45,57,98,53,97,45,55,99,52,101,45,
        56,102,50,97,45,49,98,51,99,52,100,53,101,54,102,55,48]
yes

When the backend only provides access to local time, use uuid_v7/2 with the current local UTC offset to compute the UUID timestamp using UTC:

| ?- uuid::uuid_v7('+01:00', UUID).
UUID = '018d5f3c-9b5a-7c4e-8f2a-1b3c4d5e6f70'
yes

Generating the Nil and Max UUIDs

Predicates are also provided that return the Nil and Max UUIDs:

| ?- uuid::uuid_nil(UUID).
UUID = '00000000-0000-0000-0000-000000000000'
yes

| ?- uuid::uuid_max(UUID).
UUID = 'FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF'
yes