discard

pub fn discard(r: *Reader, limit: Limit) Error!usize {
    const buffered_len = r.end - r.seek;
    const remaining: Limit = if (limit.toInt()) |n| l: {
        if (buffered_len >= n) {
            r.seek += n;
            return n;
        }
        break :l .limited(n - buffered_len);
    } else .unlimited;
    r.seek = r.end;
    const n = try r.vtable.discard(r, remaining);
    assert(n <= @backingInt(remaining));
    return buffered_len + n;
}