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https://github.com/doriantaylor/p5-data-uuid-ncname

UUID::NCName converts UUID strings to/from valid NCName productions for use in (X|HT)ML.
https://github.com/doriantaylor/p5-data-uuid-ncname

ncname perl uuid

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UUID::NCName converts UUID strings to/from valid NCName productions for use in (X|HT)ML.

Host: GitHub
URL: https://github.com/doriantaylor/p5-data-uuid-ncname
Owner: doriantaylor
License: apache-2.0
Created: 2012-12-04T18:24:27.000Z (about 12 years ago)
Default Branch: master
Last Pushed: 2022-10-14T03:52:31.000Z (over 2 years ago)
Last Synced: 2023-03-12T10:11:35.616Z (almost 2 years ago)
Topics: ncname, perl, uuid
Language: Perl
Size: 230 KB
Stars: 0
Watchers: 1
Forks: 1
Open Issues: 1
Metadata Files:
- Readme: README
- Changelog: Changes
- License: LICENSE

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README

NAME
Data::UUID::NCName - Make valid NCName tokens which are also UUIDs

VERSION
Version 0.07

SYNOPSIS
use Data::UUID::NCName qw(:all);

my $uuid = '1ff916f3-6ed7-443a-bef5-f4c85f18cd10';
my $ncn = to_ncname($uuid, version => 1);
my $ncn32 = to_ncname($uuid, version => 1, radix => 32);

# $ncn is now "EH_kW827XQ6719MhfGM0QL".
# $ncn32 is "ed74rn43o25b255puzbprrtiql" and case-insensitive.

# from Test::More, this will output 'ok':
is(from_ncname($ncn, version => 1),
$uuid, 'Decoding result matches original');

DESCRIPTION
The purpose of this module is to devise an alternative representation of
the UUID which conforms to the
constraints of various other identifiers such as NCName, and create an
isomorphic mapping between
them.

FORMAT DEPRECATION NOTICE
After careful consideration, I have decided to change the UUID-NCName
format in a minor yet incompatible way. In particular, I have moved the
quartet containing the "variant"
to the very end of
the identifier, whereas it previously was mixed into the middle
somewhere.

This can be considered an application of Postel's Law
, based on the assumption
that these identifiers will be generated through other methods, and
potentially naïvely. Like the "version" field, the "variant" field has a
limited acceptable range of values. If, for example, one were to attempt
to generate a conforming identifier by simply generating a random Base32
or Base64 string, it will be difficult to ensure that the "variant"
field will indeed conform when the identifier is converted to a standard
UUID. By moving the "variant" field out to the end of the identifier,
everything between the "version" and "variant" bookends can be generated
randomly without any further consideration, like so:

our @B64_ALPHA = ('A'..'Z', 'a'..'z', 0..9, qw(- _));

sub make_cheapo_b64_uuid_ncname () {
my @vals = map { int rand 64 } (1..20); # generate content
push @vals, 8 + int rand 4; # last digit is special
'E' . join '', map { $B64_ALPHA[$_] } @vals; # 'E' for UUID V4
}

# voilà:
my $cheap = make_cheapo_b64_uuid_ncname;
# EPrakcT1o2arqWSOuIMGSK or something

# as expected, we can decode it (version 1, naturally)
my $uu = Data::UUID::NCName::from_ncname($cheap, version => 1);
# 3eb6a471-3d68-4d9a-aaea-5923ae20c192 - UUID is valid

Furthermore, since the default behaviour is to align the bits of the
last byte to the size of the encoding symbol, and since the "variant"
bits are masked, a compliant RFC4122 UUID will *always* end with "I",
"J", "K", or "L", in *both* Base32 (case-insensitive) and Base64
variants.

Since I have already released this module prior to this format change, I
have added a "version" parameter to both "to_ncname" and "from_ncname".
The version currently defaults to 1, the new one, but will issue a
warning if not explicitly set. Later I will finally remove the warning
with 1 as the default. This should ensure that any code written during
the transition produces the correct results.

Unless you have to support identifiers generated from version 0.04
or older, you should be running these functions with "version => 1".

RATIONALE & METHOD
The UUID is a generic identifier which is large enough to be globally
unique. This makes it useful as a canonical name for data objects in
distributed systems, especially those that cross administrative
jurisdictions, such as the World-Wide Web. The representation
, however, of the UUID,
precludes it from being used in many places where it would be useful to
do so.

In particular, there are grammars for many types of identifiers which
must not begin with a digit. Others are case-insensitive, or prohibited
from containing hyphens (present in both the standard notation and
Base64URL), or indeed anything outside of "^[A-Za-z_][0-9A-Za-z_]*$".

The hexadecimal notation of the UUID has a 5/8 chance of beginning with
a digit, Base64 has a 5/32 chance, and Base32 has a 3/16 chance. As
such, the identifier must be modified in such a way as to guarantee
beginning with an alphabetic letter (or underscore "_", but some
grammars even prohibit that, so we omit it as well).

While it is conceivable to simply add a padding character, there are a
few considerations which make it more appealing to derive the initial
character from the content of the UUID itself:

* UUIDs are large (128-bit) identifiers as it is, and it is
undesirable to add meaningless syntax to them if we can avoid doing
so.

* 128 bits is an inconvenient number for aligning to both Base32 (130)
and Base64 (132), though 120 divides cleanly into 5, 6 and 8.

* The 13th quartet, or higher four bits of the
"time_hi_and_version_field" of the UUID is constant, as it indicates
the UUID's version. If we encode this value using the scheme common
to both Base64 and Base32, we get values between "A" and "P", with
the valid subset between "B" and "F".

Therefore: extract the UUID's version quartet, shift all subsequent data
4 bits to the left, zero-pad to the octet, encode with either
*base64url* or *base32*, truncate, and finally prepend the encoded
version character. Voilà, one token-safe UUID.

APPLICATIONS
XML IDs
The "ID" production appears to have been constricted, inadvertently
or otherwise, from Name in
both the XML 1.0 and 1.1 specifications, to NCName
by XML Schema Part 2
. This removes the colon
character ":" from the grammar. The net effect is that

while being a *well-formed* ID *and* valid under DTD validation, is
*not* valid per XML Schema Part 2 or anything that uses it (e.g.
Relax NG).

RDF blank node identifiers
Blank node identifiers in RDF are intended for serialization, to act
as a handle so that multiple RDF statements can refer to the same
blank node. The RDF abstract syntax specifies
that the
validity constraints of blank node identifiers be delegated to the
concrete syntax specifications. The RDF/XML syntax specification
lists the blank
node identifier as NCName. However, according to the Turtle spec
, this is a valid blank node
identifier:

_:42df00ec-30a2-431f-be9e-e3a612b325db

despite an older version
listing a
production equivalent to the more conservative NCName. NTriples
syntax is even more constrained
, given as
"^[A-Za-z][0-9A-Za-z]*$".

Generated symbols

There are only two hard things in computer science: cache
invalidation and naming things [and off-by-one errors].

-- Phil Karlton [extension of unknown origin]

Suppose you wanted to create a literate programming
system (I do).
One of your (my) stipulations is that the symbols get defined in the
*prose*, rather than the *code*. However, you (I) still want to be
able to validate the code's syntax, and potentially even run the
code, without having to commit to naming anything. You are (I am)
also interested in creating a global map of classes, datatypes and
code fragments, which can be operated on and tested in isolation,
ported to other languages, or transplanted into the more
conventional packages of programs, libraries and frameworks. The
Base32 UUID NCName representation should be adequate for placeholder
symbols in just about any programming language, save for those which
do not permit identifiers as long as 26 characters (which are
extremely scarce).

EXPORT
No subroutines are exported by default. Be sure to include at least one
of the following in your "use" statement:

:all
Import all functions.

:decode
Import decode-only functions.

:encode
Import encode-only functions.

:32 Import base32-only functions.

:58 Import base58-only functions.

:64 Import base64-only functions.

SUBROUTINES
to_ncname $UUID [, $RADIX ] [, %PARAMS ]
Turn $UUID into an NCName. The UUID can be in the canonical (hyphenated)
hexadecimal form, non-hyphenated hexadecimal, Base64 (regular and
base64url), or binary. The function returns a legal NCName equivalent to
the UUID, in either Base32, Base58, or Base64 (url), given a specified
$RADIX of 32, 58, or 64. If the radix is omitted, Base64 is assumed.

The following keyword parameters are also accepted, and override the
positional parameters where applicable:

radix 32|58|64
Either 32 or 64 to explicitly specify Base32, Base58, or Base64
output. Defaults to 64.

version 0|1
Version 0 will generate the original version of NCName identifiers,
prior to the changes noted above. Version 1 is the new version,
which is *not* backwards-compatible. The default, for a transitional
period, is to generate version 0, but complain about it. Set the
version explicitly (to 1, or to 0 if you need backwards
compatibility) to eliminate the warning messages.

align $FALSY|$TRUTHY
Align the last 4 bits to the Base32/Base64 symbol size. You almost
certainly want this, so the default is *true*. (Does not apply to
Base58.)

from_ncname $NCNAME [, $FORMAT [, $RADIX] ] [, %PARAMS ]
Turn an appropriate $NCNAME back into a UUID, where *appropriate*,
unless overridden by $RADIX, is defined beginning with one initial
alphabetic letter (A to Z, case-insensitive) followed by either:

25 Base32 characters, or
21 Base64URL characters.

The function will return "undef" immediately if it cannot match either
of these patterns. Input past the 21-character mark (for Base64) or
25-character mark (for Base32) is ignored.

This function returns a UUID of type $FORMAT, which if left undefined,
must be one of the following:

str The canonical UUID format, like so:
"33fcc995-5d10-477e-a9b4-c9cc405bbf04". This is the default.

hex The same thing, minus the hyphens.

b64 Base64.

bin A binary string.

This function also takes the new keyword-style parameters:

format
As above.

radix
As above.

version
Sets the identifier version. Defaults to version 0 with a warning.
See the note about setting an explicit "version" parameter in
"to_ncname".

align
Assume the last few bits are aligned to the symbol, as in
"to_ncname".

to_ncname_64 $UUID [, %PARAMS ]
Shorthand for Base64 NCNames.

from_ncname_64 $NCNAME [, $FORMAT | %PARAMS ]
Ditto.

to_ncname_58 $UUID [, %PARAMS ]
Shorthand for Base58 NCNames.

from_ncname_58 $NCNAME [, $FORMAT | %PARAMS ]
Ditto.

to_ncname_32 $UUID [, %PARAMS ]
Shorthand for Base32 NCNames.

from_ncname_32 $NCNAME [, $FORMAT | %PARAMS ]
Ditto.

AUTHOR
Dorian Taylor, ""

BUGS
Please report bugs/issues/etc in GitHub
.

* MetaCPAN

* GitHub repository (bugs also go here)

* AnnoCPAN: Annotated CPAN documentation

* CPAN Ratings