behnum / minimal-message-encoder

A Simple Binary Message Encoding Scheme in JS

minimal-message-encoder

Overview

A JavaScript implementation of a simple binary message encoding scheme designed for a signaling protocol. This encoding scheme is intended for passing messages between peers in a real-time communication application. The primary components include a Message class representing a message with headers and a payload, and a MessageCodec class providing methods for encoding and decoding messages.

Implementation Details

Message Structure

A message in this encoding scheme consists of a variable number of headers and a binary payload. Headers are name-value pairs, where both names and values are ASCII-encoded strings. Each header's name and value are limited to 1023 bytes independently. A message can contain a maximum of 63 headers. The message payload is limited to 256 KiB.

Message Class

The Message class has the following structure:

class Message {
  constructor() {
    this.headers = {};
    this.payload = new Uint8Array(0); // Initialize an empty payload
  }
}

MessageCodec Class

The MessageCodec class provides methods for encoding and decoding messages:

class MessageCodec {
  encode(message) {
    // ... (see code for encoding logic)
    return encodedMessage;
  }

  decode(data) {
    // ... (see code for decoding logic)
    return message;
  }
}

Encoding Logic

The encoding process involves converting headers and payload into a binary representation. The header names and values are prefixed with their lengths, and the payload size is encoded in the message header. The resulting binary message is a concatenation of encoded headers and payload information.

Decoding Logic

The decoding process involves parsing the binary message to reconstruct the original message object. It extracts header information, payload size, and payload data from the encoded message.

Usage

Creating a Message

To create a message, instantiate the Message class, set headers, and provide a payload:

const originalMessage = new Message();
originalMessage.headers = { "Content-Type": "application/json", "Authorization": "Bearer token" };
originalMessage.payload = new TextEncoder().encode("Hello, world!");

Encoding and Decoding

To encode and decode messages, use the MessageCodec class:

const codec = new MessageCodec();

// Encoding the message
const encodedData = codec.encode(originalMessage);
console.log("Encoded Data:", encodedData);

// Decoding the message
const decodedMessage = codec.decode(encodedData);
console.log("Decoded Message:", decodedMessage);

Error Handling

The implementation includes error handling for cases where the header count exceeds the limit or the payload size exceeds the maximum allowed.

Assumptions

No assumptions were made in the design and implementation beyond the specifications provided in the task description.

Notes to Developers

• Production-Grade Code: The implementation aims to be clean, simple, and proportionate to the problem's complexity. It follows best practices for input validation, error handling, and overall code readability.
• Third-Party Dependencies: The implementation refrains from using any platform built-in or third-party serializer implementations, as per the task requirements.

Contributions and Issues

Contributions to the repository are welcome. If you encounter any issues or have suggestions, please open an issue on the GitHub repository.

License

This project is licensed under the MIT License.