jhash

Overview

A fast algorithm to hash string or binary file inspired by the JSW hash. Not likes md5 or sha1, the hash sum it creates is only about 6 chars (if you use base 70).

I used it in one of my company's node project. It helps me peacefully distribute different versions of files to the CDN service.

Useful when using it in the URL hash or table lookup.

Features

• Easy to control the length of the result hash value.

• Lite and fast.

Other Language Implementations

I have implemented the core algorithm into 7 commonly used languages:

• c
• coffeescript
• go
• lua
• php
• python
• ruby

Only the coffeescript one has full API. If you only want the minimal function, go for the src/jhash.core.js file, Or require('jhash/lib/jhash.core.js')

Node

• Install

npm install jhash

• Usage

var jhash = require('jhash');
jhash.hash('test'); // output => '349o'
 
var fs = require('fs');
jhash.hash(fs.readFileSync('a.jpg'));
 
// Control the hash char set.
jhash.setSymbols('abcdef');
jhash.hash('test'); // output => 'decfddfe'
 
// Control the max length of the result hash value. Unit is bit.
jhash.setMaskLen(10);
jhash.hash('test'); // output => 'ede'
 
// New jhash instance.
myJhash = new jhash.constructor

Browser

Install it via Bower: bower install jhash.

Or download the js file from the release page: Release.

<script src='jhash.js'></script>
<script>
  jhash.hash('test'); // output => '349o'
</script> 

CLI Tool

• Install

  To use it as a command line tool, install it globally.

  npm install -g jhash
  

• Usage

  Here are some examples.

  Print help information:

    jhash -h
  

  Hash string abc, it outputs 2csX:

    jhash abc
  

  Hash a jpg image file (it will automatically detect whether the passed in argument is a file or not):

    jhash a.jpg
  

Test

Unit test

You must have installed coffeescript and mocha globally.

cake test

Collision test for 10 seconds random data

cake collision

Compare to some other hash algorithms

This is just a random test, you may need to test some real data before using it in project.

****** jhash *******
     sample: ["jg0ayq","nz9fb0","oa9iz1","4w5egf","dt7dsv","9wkm25","duu2j2","solh6y","z6rnbl","aa8ebp","g568a2"]
       time: 6.836s
 collisions: 0.000999999999995449%

****** rotating_hash *******
     sample: ["ahuz3","2hxrf3","k68zy","3cdf61","2857v2","fgua","3216o4","2i69dz","1ehpfn","1y46pv","3m1r0h"]
       time: 7.154s
 collisions: 48.626000000000005%

****** bjb2_hash *******
     sample: ["sdflvy","-g2j5ix","-1dsjyy","sezbl2","-wye5kw","-bdfy0t","-mudsaj","-4f3shn","-z1mxsl","-165mmr","q5oh58"]
       time: 16.718s
 collisions: 0.002000000000002%

****** fnv_hash *******
     sample: ["4ct07k","-pdrz0h","me11fv","t9px7i","-y120s","251qw7","h83axv","tob69f","eonk6","-6dkeny","elxam6"]
       time: 16.787s
 collisions: 0.000999999999995449%

****** oat_hash *******
     sample: ["-fg1gqa","-2k0tg","a391j2","1jd98xw","2dw8oj","-uldzx3","-t9m4me","-5z57og","6m0uqx","-17q8t0j","u8m0lo"]
       time: 19.028s
 collisions: 0.000999999999995449%

****** jsw_hash *******
     sample: ["-hm4rfv","vehfuu","jwf2v0","5c2oq3","-9xs2xt","p1ho2c","-ri84uf","op47br","-13wvwp","ek12tv","hrc6ki"]
       time: 15.702s
 collisions: 0.002999999999997449%

Benchmark

Run cake benchmark.

Intel Core i7 2.3GHz SSD

87174 ops/s.
Avr. file size 6716B.

Road Map

• Add more test cases.

The MIT License (MIT)

Apr 2014 jhash