alignedIndex

fn alignedIndex(buf_ptr: [*]u8, end_index: usize, alignment: Alignment) usize {
    // Wrapping arithmetic to avoid overflows since `end_index` isn't bounded by
    // `size`. This is always ok since the max alignment in byte units is also
    // the max value of `usize` so wrapped values are correctly aligned anyway.
    return alignment.forward(@intFromPtr(buf_ptr) +% end_index) -% @intFromPtr(buf_ptr);
}