Readme.md

Asino

Asino, a stubborn, simple and fast Bloom filter for the rest of us.

Install

$ npm install asino [-g]

require:

var Asino  = require( 'asino' );

Run Tests

to run all test files, install devDependencies:

 $ cd asino/
 # install or update devDependencies
 $ npm install 
 # run tests
 $ npm test

Constructor

Asino( [ Object opt ] )
// or
new Asino( [ Object opt ] )

Options

Default options are listed.

opt = {
	/*
	 * expected population of elements
	 */
	epop : 10000
	
	/*
	 * The max number of bytes to parse from every 
	 * input element, using the pseudo-random table.
	 * In normal mode you should specify this property
	 * generally sizing it on the expected input length.
	 *
	 * When dunce mode is on, this property is ignored,
	 * because no pseduo-random table will be generated.
	 */
	, ilen : 32
	
	/*
	 * The number of hash functions to use.
	 * The greater the number, lesser is the probability
	 * of collisions.
	 *
	 * - the false positive probability:
	 *
	 *   fpp ~= - 1 / ( 10 ^ hfn )
	 *
 	 * In dunce mode this number is limited to 16.
	 */ 
	, hfn : 6
	
	/*
	 * Dunce mode, it is off for default.
	 *
	 * It is a fast way for testing collisions/duplicates on 
	 * long inputs ( > ~ 64 bytes ), without the construction
	 * and the use of pseudo-random table, because it uses a
	 * crypto digest to simulate 16 different hash functions.
	 *
	 * However, no randomness is involved for producing values,
	 * then, for every distinct function (0-15): 
	 *
	 * Same input -> Same hash result. Every time.
	 *
	 * In dunce mode the integer produced by hash functions
	 * are limited to the range [2^24, 2^32 -1].
	 */
	, dunce: false
}

Properties

/*
 * the internal bitmap.
 */
Asino.vector

/*
 * the internal pseudo-random table used to generate k
 * indipendent hash functions.
 */
Asino.hash

/*
 * the total number of bits used for the bitmap vector.
 */
Asino.bits

/*
 * the total number of hash functions
 */
Asino.hfn

/*
 * the max bytes to parse from input
 */
Asino.ilen

/*
 * the current false positive probability
 */
Asino.fpp

Methods

Arguments between [] are optional.

/*
 * Check if an element exists.
 * When it returns false, we are sure that the element
 * does not exist in the filter. 
 * When it returns true, there is a probability of a
 * false positive, equal to the current fpp.
 */
Asino#key( Buffer data ) : Boolean

/*
 * try to add the element if it doesn't exist.
 * It returns the same result of Asino#key
 */
Asino#try( Buffer data ) : Boolean

/*
 * Reset/regenerate the filter
 */
Asino#yoke() : Asino

/*
 * Re-build Bloom filter, via a config object.
 */
Asino#grow( [ Object opt ] ) : Asino

opt : { [ hfn: Number ] [, epop: Number] [, ilen : Number] [, dunce: Boolean] }

See examples.

MIT License

Copyright (c) 2017-present < Guglielmo Ferri : [email protected] >

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.