75 lines
3.0 KiB
Markdown
75 lines
3.0 KiB
Markdown
slugid - Compressed UUIDs for Node.js
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=====================================
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<img src="https://tools.taskcluster.net/lib/assets/taskcluster-120.png" />
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[](http://travis-ci.org/taskcluster/slugid)
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[](https://github.com/taskcluster/slugid/blob/master/LICENSE)
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A node.js module for generating v4 UUIDs and encoding them into 22 character
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URL-safe base64 slug representation (see [RFC 4648 sec.
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5](http://tools.ietf.org/html/rfc4648#section-5)).
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Slugs are url-safe base64 encoded v4 uuids, stripped of base64 `=` padding.
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There are two methods for generating slugs - `slugid.v4()` and `slugid.nice()`.
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The `slugid.v4()` method returns a slug from a randomly generated v4 uuid. The
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`slugid.nice()` method returns a v4 slug which conforms to a set of "nice"
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properties. At the moment the only "nice" property is that the slug starts with
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[A-Za-f], which in turn implies that the first (most significant) but of its
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associated uuid is set to 0.
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The purpose of the `slugid.nice()` method is to support having slugids which
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can be used in more contexts safely. Regular slugids can safely be used in
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urls, and for example in AMQP routing keys. However, slugs beginning with `-`
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may cause problems when used as command line parameters.
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In contrast, slugids generated by the `slugid.nice()` method can safely be used
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as command line parameters. This comes at a cost to entropy (121 bits vs 122
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bits for regular v4 slugs).
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Slug consumers should consider carefully which of these two slug generation
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methods to call. Is it more important to have maximum entropy, or to have
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slugids that do not need special treatment when used as command line
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parameters? This is especially important if you are providing a service which
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supplies slugs to unexpecting tool developers downstream, who may not realise
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the risks of using your regular v4 slugs as command line parameters, especially
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since this would arise only as an intermittent issue (one time in 64).
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Generated slugs take the form `[A-Za-z0-9_-]{22}`, or more precisely:
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* `slugid.v4()` slugs conform to
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`[A-Za-z0-9_-]{8}[Q-T][A-Za-z0-9_-][CGKOSWaeimquy26-][A-Za-z0-9_-]{10}[AQgw]`
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* `slugid.nice()` slugs conform to
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`[A-Za-f][A-Za-z0-9_-]{7}[Q-T][A-Za-z0-9_-][CGKOSWaeimquy26-][A-Za-z0-9_-]{10}[AQgw]`
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RFC 4122 defines the setting of 6 bits of the v4 UUID which determines these
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regular expressions.
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```js
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var slugid = require('slugid');
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// Generate "nice" URL-safe base64 encoded UUID version 4 (random)
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var slug = slugid.nice(); // a8_YezW8T7e1jLxG7evy-A
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```
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Encode / Decode
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---------------
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```js
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var slugid = require('slugid');
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// Generate URL-safe base64 encoded UUID version 4 (random)
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var slug = slugid.v4();
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// Get UUID on the form xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
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var uuid = slugid.decode(slug);
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// Compress to slug again
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assert(slug == slugid.encode(uuid));
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```
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License
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-------
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The `slugid` library is released on the MIT license, see the `LICENSE` for
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complete license.
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