rolling-hash

compute rolling hashes

example

every 8kb, emit an md5 hash:

var rolling = require('rolling-hash');
var fs = require('fs');
var file = process.argv[2];

var rh = rolling('md5', 1024 * 8);
rh.on('hash', function (h) {
    console.log(h.toString('hex'));
});
fs.createReadStream(file).pipe(rh);

output:

$ node example/roll.js ~/media/vector/browserify.svg 
6ec02fc2cbed94a6880f96f3b612f185
30f47708feab6543bb6eb20df734554b
e38f209cc5889c995b0040671cff722f
5fa9a0ddd728633710bc76f55073417e
fb78a6057031063b490b547658da90b3
3c9d4359900dd8d38cc20624b25e0993
b0b4be62211604fea64ef1c6665060c6
29ef502933bbeba6fc067f3a676c51c8
0b165a397b709a0ad4ba1cc50e739e6a
699cbcc58ca7e875c3acc177e98254ca
7d846fe3b83efe09846b22c42205aeec

methods

var rolling = require('rolling-hash')

var rh = rolling(algorithm, opts)

Create a rolling hash writable stream rh given a hashing algorithm.

If algorithm is a string, the names from crypto.createHash() will be used and you can optionally set the kind of encoding to get back with opts.encoding, default: 'buffer'.

Otherwise algorithm(buf) should be a function that returns the hash of the supplied buffer buf.

opts should have an opts.size that defines the number of bytes between starting a new hash.

If opts is a number, use it as the opts.size.

events

rh.on('hash', function (hash) {})

This event fires with hash, the result of the algorithm function.

usage

usage: rolling-hash FILE OPTIONS

OPTIONS are:

  -s SIZE, --size SIZE       Print a hash every SIZE bytes.
  -a ALGO, --algorithm ALGO  Use ALGO as the hash algorithm. Default: md5
  -e ENC, --encoding ENC     Hash encoding to use. Default: hex

Use "-" as FILE to read from stdin.

install

With npm, to get the library do:

npm install rolling-hash

and to get the rolling-hash command do:

npm install -g rolling-hash

license

MIT