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
19 FILE_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 */
iob_pad(struct io_buffer * iobuf,size_t min_len)44 void 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