Fingerprint

Fingeprint objects and arrays.

Usage

This library can be used to create a fingerprint for: Objects, Arrays and primitives such as String and Number. You can combine these fingerprinting techniques to create fingerprints for complex, composite object structures and thus create a unique fingerprint for any data-structure. This technique is often used for caching purposes.

Permit-Authorize uses fingerprinting for its caching, mostly to identify repeated access requests and then returning the cached authorization result for that fingerprint instead of recalculating which drastically improves authorization performance!

Array

finger-printer = (array) ->
  new ArrayFingerPrint array

access-request := ['hello', 'goodbye']

finger-printer(access-request).fingerprint!

Object

finger-printer = (obj) ->
  new ObjectFingerPrint obj

access-request := {subject: subj, role: 'editor', object: post, ctx: 'admin'}

finger-printer(access-request).fingerprint!`

For any object, the ObjectFingerPrint will try to call a hash function on the object if available, then a fingerprint function and finally fall back to doing a JSON stringify that is md5'ed.

This is in order to avoid expensive hash calculations for each object. Say you have a user object, it is much more efficient to add a fingerprint method which returns the unique id or email as the fingerprint key.

TODO

Add Fingerprint method to fingerprint an Object or Array recursively.

Licence

MIT License Copyright 2014-2015 Kristian Mandrup

See LICENSE file