@polkajs/rlp

About

Recursive Length Prefix implementation

The purpose of RLP (Recursive Length Prefix) is to encode arbitrarily nested arrays of binary data, and RLP is the main encoding method used to serialize objects in Ethereum. The only purpose of RLP is to encode structure; encoding specific atomic data types (eg. strings, ints, floats) is left up to higher-order protocols; in Ethereum integers must be represented in big endian binary form with no leading zeroes (thus making the integer value zero be equivalent to the empty byte array).

Explanation

API

Install

npm install --save @polkajs/rlp

Require Module

const RLP = require('@polkajs/rlp');

ENCODE

let encode = RLP.encode(['hello']);
console.log(encode);
// <Buffer c6 85 68 65 6c 6c 6f>

c6 - represents an array with a 6 byte buffer to follow (0xc6 - 0xc0)

85 - represents a string or number with the size of 5 (0x85 - 0x80)

DECODE

let decode = RLP.decode(encode);
console.log(decode);
// [ <Buffer 68 65 6c 6c 6f> ] (ascii)

let str = decode[0].toString();
console.log(str);
// 'hello'

DECODE_STR

If you are only working with arrays and strings, this method has better decoding

const arr = ['a', 'abc', 5];

const encode = RLP.encode(arr);
const decode_str = RLP.decode_str(encode);
console.log(decode_str);
// ['a', 'abc', '\x05']

Visual QUE:

First byte of an encoded item

    x: single byte, itself
    |
    |
0x7f == 127

0x80 == 128
    |
    x: [0, 55] byte long string, x-0x80 == length
    |
0xb7 == 183

0xb8 == 184
    |
    x: [55, ] long string, x-0xf8 == length of the length
    |
0xbf == 191

0xc0 == 192
    |
    x: [0, 55] byte long list, x-0xc0 == length
    |
0xf7 == 247

0xf8 == 248
    |
    x: [55, ] long list, x-0xf8 == length of the length
    |
0xff == 255

ISC License (ISC) Copyright 2017 Copyright (c) 2004-2010 by Internet Systems Consortium, Inc. ("ISC") Copyright (c) 1995-2003 by Internet Software Consortium

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.