PEE/src/bitstream.ts

import { BitstreamReader as br, BitstreamWriter as bw } from '@astronautlabs/bitstream';

export const revbyte = (n: number, len = 8) => {
    let acc = 0;
    let n2 = n;
    let len2 = len;
    while (len2) {
        // can't use bitshifts or binray ops or else becomes negative
        acc = (acc * 2) + (n2 & 1);
        n2 >>= 1;
        len2--;
    }
    return acc;
};

export class BitstreamReader extends br {
    rtotal = 0;

    addBuffer(hidden: Buffer) {
        const inp = Buffer.from(hidden);
        for (let i = 0; i < inp.byteLength; ++i)
            inp[i] = revbyte(inp[i]);
        super.addBuffer(inp);
    }

    readSync(len: number) {
        const v = super.readSync(len);
        this.rtotal += len;
        return revbyte(v, len);
    }
}

export type Writable = {
    write: (chunk: Buffer) => void;
};

export class BitstreamWriter extends bw {
    wtotal = 0;

    constructor(private w: Writable) {
        super({
            write: (c) => {
                const inp = Buffer.from(c);
                for (let i = 0; i < inp.byteLength; ++i)
                    inp[i] = revbyte(inp[i]);
                this.w.write(inp);
            }
        });
    }

    write(length: number, value: number): void {
        this.wtotal += length;
        if (length) {
            //tconsole.log(length, value)
            value = revbyte(value, length);
        }
        super.write(length, value);
    }
}