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This file is part of Logtalk <https://logtalk.org/>  
SPDX-FileCopyrightText: 1998-2026 Paulo Moura <pmoura@logtalk.org>  
SPDX-License-Identifier: Apache-2.0

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
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See the License for the specific language governing permissions and
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`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.

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](../../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


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


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
