parseIntSizeSuffix

pub fn parseIntSizeSuffix(buf: []const u8, digit_base: u8) ParseIntError!usize {
    var without_B = buf;
    if (mem.endsWith(u8, buf, "B")) without_B.len -= 1;
    var without_i = without_B;
    var magnitude_base: usize = 1000;
    if (mem.endsWith(u8, without_B, "i")) {
        without_i.len -= 1;
        magnitude_base = 1024;
    }
    if (without_i.len == 0) return error.InvalidCharacter;
    const orders_of_magnitude: usize = switch (without_i[without_i.len - 1]) {
        'k', 'K' => 1,
        'M' => 2,
        'G' => 3,
        'T' => 4,
        'P' => 5,
        'E' => 6,
        'Z' => 7,
        'Y' => 8,
        'R' => 9,
        'Q' => 10,
        else => 0,
    };
    var without_suffix = without_i;
    if (orders_of_magnitude > 0) {
        without_suffix.len -= 1;
    } else if (without_i.len != without_B.len) {
        return error.InvalidCharacter;
    }
    const multiplier = math.powi(usize, magnitude_base, orders_of_magnitude) catch |err| switch (err) {
        error.Underflow => unreachable,
        error.Overflow => |e| return e,
    };
    const number = try std.fmt.parseInt(usize, without_suffix, digit_base);
    return math.mul(usize, number, multiplier);
}