next

    pub fn next(it: *LoadCommandIterator) error{InvalidMachO}!?LoadCommand {
        if (it.next_index >= it.ncmds) return null;

        const hdr = it.r.peekStruct(load_command, .little) catch |err| switch (err) {
            error.ReadFailed => unreachable,
            error.EndOfStream => return error.InvalidMachO,
        };
        const data = it.r.take(hdr.cmdsize) catch |err| switch (err) {
            error.ReadFailed => unreachable,
            error.EndOfStream => return error.InvalidMachO,
        };

        it.next_index += 1;
        return .{ .hdr = hdr, .data = data };
    }