util.js

export function concatWithLength(...arrays) {
    let totalLength = arrays.reduce((sum, arr) => sum + 2 + arr.length, 0);
    let combined = new Uint8Array(totalLength);
    let offset = 0;

    for (const arr of arrays) {
        combined[offset] = (arr.length >> 8) & 0xff;
        combined[offset + 1] = arr.length & 0xff;
        combined.set(arr, offset + 2);
        offset += 2 + arr.length;
    }

    return combined;
}

export function splitWithLength(combined) {
    const arrays = [];
    let offset = 0;

    while (offset < combined.length) {
        const len = (combined[offset] << 8) | combined[offset + 1];
        arrays.push(combined.slice(offset + 2, offset + 2 + len));
        offset += 2 + len;
    }

    return arrays;
}