mancala/src/rtmt/encode_decode_message.ts

import { decodeText, encodeText } from "./byte_util";
import { Bytes } from "./rtmt";

const headerLenght = 4

export type Message = {
    channel: string,
    data: Bytes,
}
 
//
// channel is string, message is byte array
//
export function encode(message: Message) {
    const { channel, data } = message
    const channelLenght = channel.length
    const messageLenght = data.length
    const totalLenght = headerLenght + channelLenght + messageLenght

    const buffer = new ArrayBuffer(totalLenght);
    const view = new DataView(buffer);

    view.setUint32(0, channelLenght);

    const channelBytes = encodeText(channel)

    let count = headerLenght
    channelBytes.forEach((byte: any) => {
        view.setUint8(count, byte)
        count++
    })

    data.forEach((byte: any) => {
        view.setUint8(count, byte)
        count++
    })

    return buffer
}

// 
// return { channel :  string, message :  byte array} 
//
export function decode(bytes: Bytes): Message {
    const channelLenght = bytes.readInt32BE(0)
    const channel = decodeText(
        bytes.slice(headerLenght, headerLenght + channelLenght))

    const message = bytes.slice(headerLenght + channelLenght)

    return {
        "channel": channel,
        "data": message,
    }
}