.. _library_uuid:

uuid

This library implements a Universally unique identifier (UUID) generator. Currently only version 1 and version 4 UUIDs are supported. 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.

The generation of version 4 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.

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

See also the ids and ulid libraries.

API documentation

Open the `../../docs/library_index.html#uuid <../../docs/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

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 the null UUID

A predicate is also provided that returns the null UUID:

::

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