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Bencode

npm npm downloads build status

A node library for encoding and decoding bencoded data, according to the BitTorrent specification.

Index

About BEncoding

from Wikipedia:

Bencode (pronounced like B encode) is the encoding used by the peer-to-peer file sharing system BitTorrent for storing and transmitting loosely structured data.

It supports four different types of values:

  • byte strings
  • integers
  • lists
  • dictionaries

Bencoding is most commonly used in torrent files. These metadata files are simply bencoded dictionaries.

Install with npm

npm install bencode

Performance

encode buffer

package version op/sec
bencode 1.0.0 41,880
dht.js 0.2.16 36,824
dht-bencode 0.1.2 25,232
bencoding 0.0.1 19,129
bncode 0.5.3 16,567

decode to buffer

package version op/sec
bencode 1.0.0 67,351
dht-bencode 0.1.2 64,445
bencoding 0.0.1 48,415
dht.js 0.2.16 41,648
bncode 0.5.3 3,188

Benchmarks run on an Intel Core i7-5500U @ 2.40Ghz with node v6.1.0 & GNU/Linux 4.4.0

To run the benchmarks simply use

npm run bench

Usage

var bencode = require( 'bencode' )

You can also use node-bencode with browserify to be able to use it in a lot of modern browsers.

Encoding

var data = {
  string: 'Hello World',
  integer: 12345,
  dict: {
    key: 'This is a string within a dictionary'
  },
  list: [ 1, 2, 3, 4, 'string', 5, {} ]
}

var result = bencode.encode( data )

NOTE As of [email protected], boolean values will be cast to integers (false -> 0, true -> 1).

Output

d4:dictd3:key36:This is a string within a dictionarye7:integeri12345e4:listli1ei2ei3ei4e6:stringi5edee6:string11:Hello Worlde

Decoding

var data   = new Buffer( 'd6:string11:Hello World7:integeri12345e4:dictd3:key36:This is a string within a dictionarye4:listli1ei2ei3ei4e6:stringi5edeee' )
var result = bencode.decode( data )

Output

{
  string: <Buffer 48 65 6c 6c 6f 20 57 6f 72 6c 64>,
  integer: 12345,
  dict: {
    key: <Buffer 54 68 69 73 20 69 73 20 61 20 73 74 72 69 6e 67 20 77 69 74 68 69 6e 20 61 20 64 69 63 74 69 6f 6e 61 72 79>
  },
  list: [ 1, 2, 3, 4, <Buffer 73 74 72 69 6e 67>, 5, {} ]
}

Automagically convert bytestrings to strings:

var result = bencode.decode( data, 'utf8' )

Output

{
  string: 'Hello World',
  integer: 12345,
  dict: {
    key: 'This is a string within a dictionary'
  },
  list: [ 1, 2, 3, 4, 'string', 5, {} ]
}

API

The API is compatible with the abstract-encoding specification.

bencode.encode( data, [buffer], [offset] )

Buffer | Array | String | Object | Number | Boolean data Buffer buffer Number offset

Returns Buffer

bencode.decode( data, [start], [end], [encoding] )

Buffer data Number start Number end String encoding

If encoding is set, bytestrings are automatically converted to strings.

Returns Object | Array | Buffer | String | Number

bencode.byteLength( value ) or bencode.encodingLength( value )

Buffer | Array | String | Object | Number | Boolean value