README.md
1iMurmurHash.js
2==============
3
4An incremental implementation of the MurmurHash3 (32-bit) hashing algorithm for JavaScript based on [Gary Court's implementation](https://github.com/garycourt/murmurhash-js) with [kazuyukitanimura's modifications](https://github.com/kazuyukitanimura/murmurhash-js).
5
6This version works significantly faster than the non-incremental version if you need to hash many small strings into a single hash, since string concatenation (to build the single string to pass the non-incremental version) is fairly costly. In one case tested, using the incremental version was about 50% faster than concatenating 5-10 strings and then hashing.
7
8Installation
9------------
10
11To use iMurmurHash in the browser, [download the latest version](https://raw.github.com/jensyt/imurmurhash-js/master/imurmurhash.min.js) and include it as a script on your site.
12
13```html
14<script type="text/javascript" src="/scripts/imurmurhash.min.js"></script>
15<script>
16// Your code here, access iMurmurHash using the global object MurmurHash3
17</script>
18```
19
20---
21
22To use iMurmurHash in Node.js, install the module using NPM:
23
24```bash
25npm install imurmurhash
26```
27
28Then simply include it in your scripts:
29
30```javascript
31MurmurHash3 = require('imurmurhash');
32```
33
34Quick Example
35-------------
36
37```javascript
38// Create the initial hash
39var hashState = MurmurHash3('string');
40
41// Incrementally add text
42hashState.hash('more strings');
43hashState.hash('even more strings');
44
45// All calls can be chained if desired
46hashState.hash('and').hash('some').hash('more');
47
48// Get a result
49hashState.result();
50// returns 0xe4ccfe6b
51```
52
53Functions
54---------
55
56### MurmurHash3 ([string], [seed])
57Get a hash state object, optionally initialized with the given _string_ and _seed_. _Seed_ must be a positive integer if provided. Calling this function without the `new` keyword will return a cached state object that has been reset. This is safe to use as long as the object is only used from a single thread and no other hashes are created while operating on this one. If this constraint cannot be met, you can use `new` to create a new state object. For example:
58
59```javascript
60// Use the cached object, calling the function again will return the same
61// object (but reset, so the current state would be lost)
62hashState = MurmurHash3();
63...
64
65// Create a new object that can be safely used however you wish. Calling the
66// function again will simply return a new state object, and no state loss
67// will occur, at the cost of creating more objects.
68hashState = new MurmurHash3();
69```
70
71Both methods can be mixed however you like if you have different use cases.
72
73---
74
75### MurmurHash3.prototype.hash (string)
76Incrementally add _string_ to the hash. This can be called as many times as you want for the hash state object, including after a call to `result()`. Returns `this` so calls can be chained.
77
78---
79
80### MurmurHash3.prototype.result ()
81Get the result of the hash as a 32-bit positive integer. This performs the tail and finalizer portions of the algorithm, but does not store the result in the state object. This means that it is perfectly safe to get results and then continue adding strings via `hash`.
82
83```javascript
84// Do the whole string at once
85MurmurHash3('this is a test string').result();
86// 0x70529328
87
88// Do part of the string, get a result, then the other part
89var m = MurmurHash3('this is a');
90m.result();
91// 0xbfc4f834
92m.hash(' test string').result();
93// 0x70529328 (same as above)
94```
95
96---
97
98### MurmurHash3.prototype.reset ([seed])
99Reset the state object for reuse, optionally using the given _seed_ (defaults to 0 like the constructor). Returns `this` so calls can be chained.
100
101---
102
103License (MIT)
104-------------
105Copyright (c) 2013 Gary Court, Jens Taylor
106
107Permission is hereby granted, free of charge, to any person obtaining a copy of
108this software and associated documentation files (the "Software"), to deal in
109the Software without restriction, including without limitation the rights to
110use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
111the Software, and to permit persons to whom the Software is furnished to do so,
112subject to the following conditions:
113
114The above copyright notice and this permission notice shall be included in all
115copies or substantial portions of the Software.
116
117THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
118IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
119FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
120COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
121IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
122CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
123