binary-data

Declarative binary data encoder / decoder. This module works almost like as binary or restructure but provided modern and clean api. It inspired by abstract-encoding interface.

Support

Usage

decode

const { decode, createDecode, types: { uint8, array, string } } = require('binary-data')
 
// 1. Define your own schema as plain object
const protocol = {
  type: uint8,
  value: array(string(null), uint8)
}
 
const message = Buffer.from([1, 2, 3, 4, 5, 6, 0]);
 
// Just decode message
const packet = decode(message, protocol)
 
// 2 Also you may decode messages from streams
const net = require('net');
 
const socket = net.createConnection({ port: 8124 });
const istream = createDecode(protocol);
 
socket.pipe(istream).on('data', packet => {
  console.log(packet.type, packet.value);
});

encode

const { encode, createEncode, types: { uint8, string } } = require('binary-data')
 
const protocol = {
  type: uint8,
  value: string(uint8)
}
 
const hello = {
  type: 12,
  value: 'my random data'
}
 
// Just encode message
const ostream = encode(hello, protocol);
const packet = ostream.slice();
 
// Or you may encode messages into a stream
const net = require('net');
 
const ostream = createEncode(protocol);
const socket = net.createConnection({ port: 8124 }, () => {
  ostream.write(hello);
});
 
ostream.pipe(socket);
 
// You may combine multiple schemes into one stream
const ostream = createEncode();
 
encode(obj1, ostream, protocol1);
encode(obj2, ostream, protocol2);
encode(obj3, ostream, protocol3);
 
const packet = ostream.slice();
 

See stun or dtls module for complete example.

Perfomance

Decoding DTLS ClientHello packet, nodejs 10.14.1 / Ubuntu 16.04 x64

name	time
binary data	637.900ms
binary	2229.218ms

API

• encode(obj: any, [target: BinaryStream], type: Object): BinaryStream
• decode(source: BinaryStream|Buffer, type: Object): any
• encodingLength(item: any, type: Object): Number
• createEncodeStream([type: Object]): BinaryStream
• createDecodeStream([type: Object|Buffer]): BinaryStream
• createEncode([type: Object]): BinaryStream
• createDecode([type: Object|Buffer]): BinaryStream
• Types
  • (u)int(8, 16, 24, 32, 40, 48)(be, le)
  • (double, float)(be, le)
  • array(type: Object, length: number|Object|Function, lengthType: string)
  • string(length)
  • bool(type: any)
  • buffer(length)
  • reserved(type, count)
  • when(fn: function(context): boolean, type)

decode(source: BinaryStream|Buffer, type: Object): any

Reads any data from stream rstream using data type type. See examples above.

encode(obj: any, [target: BinaryStream], type: Object): BinaryStream

Writes any data obj to stream target using data type type. See examples above.

encodingLength(item: any, type: Object): Number

Return the amount of bytes needed to encode item using type.

createEncodeStream([type: Object]): BinaryStream

createEncode([type: Object]): BinaryStream

Create instance of BinaryStream.

createDecodeStream([type: Object|Buffer]): BinaryStream

createDecode([type: Object|Buffer]): BinaryStream

Create instance of BinaryStream.

types: Object

Contains all primitive data types.

Types

(u)int(8, 16, 24, 32, 40, 48)(be, le)

Low-level integer types.

const schema = {
  type: int8
}
 
// define int64 as buffer and use your loved library for big numbers
const int64 = buffer(8)

(double, float)(be, le)

Low-level floating-point types.

const schema = {
  size: doublele
}

array(type: Object, length: number|Object|Function, lengthType: string)

Array of low-level or user defined types. Argument type should be primitive type or user defined scheme. Argument length should be a number, number type or function. Argument lengthType should be bytes or count (default).

array(uint8, 3) // 3 x uint8
 
const schema = {
  length: uint8,
  type: uint32be,
  items: array(uint16, ({node}) => node.length, 'bytes')
}
 
// difference between `bytes` or `count`
 
array(uint16, uint8)
// |   0x2  | 0x0 0x1 | 0x0 0x2 |
// | length | item 1  |  item 2 |
// bytes = 1 + 4, length = 2
 
array(uint16, uint8, 'bytes')
// |   0x4  | 0x0 0x1 | 0x0 0x2 |
// | length | item 1  |  item 2 |
// bytes = 1 + 4, length = 4

string(length)

Low-level string type. Argument length can be number, null for C - strings, type for size-prefixed data or function.

bool(type: any)

Convert provided type to / from boolean. Argument type should be an number type.

const schema = bool(uint8)
const rstream = createDecodeStream(buf) // 0x01 0
 
decode(rstream, schema) // return true
decode(rstream, schema) // return false

buffer(length: Object|null|number)

Low-level buffer type. Argument length can be number, number type for size-prefixed data, function or null.

buffer(5) // buffer should be 5 bytes
 
buffer(uint8) // length prefixed buffer
// |   0x3  | 0xa 0xb 0xc
// | length | data
 
const packet = {
  header: {
    length: uint16be
  },
  data: buffer(({node}) => node.header.length % 2) // function should return actual length
}

reserved(type, count)

Special type to skip any data. Argument count should be a number, number type or function.

const packet = {
  type: uint8,
  _padding: reserved(uint8, 3)
}
 
decode(rstream, packet) // return { type }

when(fn: function(context): boolean, type)

Special type for conditions. Argument fn should be a function and should return boolean value. The type argument will be evaluated when the first one returns positive value.

const schema = {
  type: uint8,
  bytes: when(({ node }) => node.type === 1, string(uint16be)),
  list: when(({ node }) => node.type === 2, array(uint32be, uint8))
}

select(when, ..., defaultType)

The second type for conditions. The same as switch operator in js. Argument defaultType may be any known type excluding user schemas.

const schema = {
  id: uint8,
  payload: select(when(({ node }) => node.id === 1, string(uint16be)), buffer(uint16be))
}

License

MIT, 2017 (c) Dmitriy Tsvettsikh