1/*
2 * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License as
6 * published by the Free Software Foundation; either version 2 of the
7 * License, or any later version.
8 *
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12 * General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
17 */
18
19FILE_LICENCE ( GPL2_OR_LATER );
20
21/**
22 * @file
23 *
24 * I/O buffer padding
25 *
26 */
27
28#include <string.h>
29#include <gpxe/iobuf.h>
30
31/**
32 * Pad I/O buffer
33 *
34 * @v iobuf		I/O buffer
35 * @v min_len		Minimum length
36 *
37 * This function pads and aligns I/O buffers, for devices that
38 * aren't capable of padding in hardware, or that require specific
39 * alignment in TX buffers.  The packet data will end up aligned to a
40 * multiple of @c IOB_ALIGN.
41 *
42 * @c min_len must not exceed @v IOB_ZLEN.
43 */
44void iob_pad ( struct io_buffer *iobuf, size_t min_len ) {
45	void *data;
46	size_t len;
47	size_t headroom;
48	signed int pad_len;
49
50	assert ( min_len <= IOB_ZLEN );
51
52	/* Move packet data to start of I/O buffer.  This will both
53	 * align the data (since I/O buffers are aligned to
54	 * IOB_ALIGN) and give us sufficient space for the
55	 * zero-padding
56	 */
57	data = iobuf->data;
58	len = iob_len ( iobuf );
59	headroom = iob_headroom ( iobuf );
60	iob_push ( iobuf, headroom );
61	memmove ( iobuf->data, data, len );
62	iob_unput ( iobuf, headroom );
63
64	/* Pad to minimum packet length */
65	pad_len = ( min_len - iob_len ( iobuf ) );
66	if ( pad_len > 0 )
67		memset ( iob_put ( iobuf, pad_len ), 0, pad_len );
68}
69