@8kb/bit.io/read.js

`bit.io` is a js/ts library for reading individual bits from an `ArrayBuffer`.

export const divide = (divident, divisor) => {
    const remainder = divident % divisor;
    return [
        (divident - remainder) / divisor,
        remainder,
    ];
};
export const read_bit = (ab) => {
    const ua = new Uint8Array(ab);
    const bit_length = ab.byteLength * 8;
    return (index) => {
        if (index < 0 || index >= bit_length)
            return 'out of range';
        if (!Number.isInteger(index))
            return 'invalid index';
        const [byte_index, bit_index] = divide(index, 8);
        const byte = ua[byte_index];
        let result = byte << bit_index;
        result &= 255;
        return result >> 7;
    };
};
export const read_bits = (ab) => {
    const bit_length = ab.byteLength * 8;
    const read_bit_by_index = read_bit(ab);
    const result = [];
    for (let i = 0; i < bit_length; i++)
        result.push(read_bit_by_index(i));
    return result;
};