bencode

Note

This is one of 215 standalone projects, maintained as part of the @thi.ng/umbrella ecosystem and anti-framework.

🚀 Please help me to work full-time on these projects by sponsoring me. Thank you! ❤️

• About
  • Features / behaviors
    • Booleans
    • String handling
    • Floating point values
• Status
• Installation
• Dependencies
• API
• Authors
• License

About

Binary Bencode encoder & decoder for structured data.

Features / behaviors

Booleans

Will be converted to 0 or 1 integers.

String handling

All JS strings will be UTF-8 encoded. To write raw bytes without transformation, wrap them as Uint8Array. These too will be written as Bencode strings (e.g. len:xxx...), but are used as is.

When decoding, UTF-8 is used by default, but can be disabled by passing false as 2nd argument to decode(). In that case, strings will be decoded as Uint8Arrays, with the exception of dictionary keys, which will be decoded via String.fromCharCode().

Floating point values

This implementation has optional (non-standard) support for floating point values. If these are not desired (e.g. for compatibility reasons), all numeric values MUST be pre-rounded to integers. The encoder only chooses the custom float encoding iff a number has a fractional part. Floats are encoded similarly to standard ints (i.e. as text), but using f as prefix. Furthermore, only floats with an absolute value in the semi-open [1e-6,1e21) interval can be encoded. Float values requiring exponential notation will throw an error during encoding.

Status

STABLE - used in production

Search or submit any issues for this package

Installation

yarn add @thi.ng/bencode

ESM import:

import * as bc from "@thi.ng/bencode";

Browser ESM import:

<script type="module" src="https://esm.run/@thi.ng/bencode"></script>

JSDelivr documentation

For Node.js REPL:

const bc = await import("@thi.ng/bencode");

Package sizes (brotli'd, pre-treeshake): ESM: 1.21 KB

Dependencies

• @thi.ng/api
• @thi.ng/arrays
• @thi.ng/checks
• @thi.ng/errors
• @thi.ng/strings
• @thi.ng/transducers
• @thi.ng/transducers-binary

Note: @thi.ng/api is in most cases a type-only import (not used at runtime)

API

Generated API docs

import { encode, decode } from "@thi.ng/bencode";
import { hexDump } from "@thi.ng/transducers-binary";

[...hexDump({}, encode({ foo: "bar", "baz": [0, 1, 2, 3], "pi": Math.PI }))]
// [ '00000000 | 64 33 3a 62 61 7a 6c 69 30 65 69 31 65 69 32 65 | d3:bazli0ei1ei2e',
//   '00000010 | 69 33 65 65 33 3a 66 6f 6f 33 3a 62 61 72 32 3a | i3ee3:foo3:bar2:',
//   '00000020 | 70 69 66 33 2e 31 34 31 35 39 32 36 35 33 35 38 | pif3.14159265358',
//   '00000030 | 39 37 39 33 65 65 00 00 00 00 00 00 00 00 00 00 | 9793ee..........' ]

// Uin8Array values are written verbatim (as Bencode strings)
[...hexDump({}, encode({ foo: new Uint8Array([0, 1 ,2, 3]) }))]
// [ '00000000 | 64 33 3a 66 6f 6f 34 3a 00 01 02 03 65 00 00 00 | d3:foo4:....e...' ]

const bytes = encode({ foo: [1, "a", { bar: "baz"}, [42]] });
// Uint8Array [ 100, 51, 58, 102, 111, 111, 108, 105, 49, 101, 49, ... ]

decode(bytes)
// { foo: [ 1, 'a', { bar: 'baz' }, [ 42 ] ] }

// decode w/o UTF8 decoding
// (note: dictionary keys will ALWAYS be utf8 decoded)
decode(bytes, false)
// { foo: [ 1, [ 97 ], { bar: [ 98, 97, 122 ] }, [ 42 ] ] }

Authors

• Karsten Schmidt

If this project contributes to an academic publication, please cite it as:

@misc{thing-bencode,
  title = "@thi.ng/bencode",
  author = "Karsten Schmidt",
  note = "https://thi.ng/bencode",
  year = 2016
}

License

© 2016 - 2026 Karsten Schmidt // Apache License 2.0