data.c revision 208012 
1/*	$NetBSD: data.c,v 1.8 2000/04/02 11:10:53 augustss Exp $	*/
2
3/*
4 * Copyright (c) 1999 Lennart Augustsson <augustss@netbsd.org>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <sys/cdefs.h>
30__FBSDID("$FreeBSD: head/lib/libusbhid/data.c 208012 2010-05-12 22:50:23Z thompsa $");
31
32#include <sys/param.h>
33#include <assert.h>
34#include <stdlib.h>
35#include "usbhid.h"
36
37int
38hid_get_data(const void *p, const hid_item_t *h)
39{
40	const uint8_t *buf;
41	uint32_t hpos;
42	uint32_t hsize;
43	uint32_t data;
44	int i, end, offs;
45
46	buf = p;
47
48	/* Skip report ID byte. */
49	if (h->report_ID > 0)
50		buf++;
51
52	hpos = h->pos;			/* bit position of data */
53	hsize = h->report_size;		/* bit length of data */
54
55	/* Range check and limit */
56	if (hsize == 0)
57		return (0);
58	if (hsize > 32)
59		hsize = 32;
60
61	offs = hpos / 8;
62	end = (hpos + hsize) / 8 - offs;
63	data = 0;
64	for (i = 0; i <= end; i++)
65		data |= buf[offs + i] << (i*8);
66
67	/* Correctly shift down data */
68	data >>= hpos % 8;
69	hsize = 32 - hsize;
70
71	/* Mask and sign extend in one */
72	if ((h->logical_minimum < 0) || (h->logical_maximum < 0))
73		data = (int32_t)((int32_t)data << hsize) >> hsize;
74	else
75		data = (uint32_t)((uint32_t)data << hsize) >> hsize;
76
77	return (data);
78}
79
80void
81hid_set_data(void *p, const hid_item_t *h, int data)
82{
83	uint8_t *buf;
84	uint32_t hpos;
85	uint32_t hsize;
86	int i, end, offs, mask;
87
88	buf = p;
89
90	/* Set report ID byte. */
91	if (h->report_ID > 0)
92		*buf++ = h->report_ID & 0xff;
93
94	hpos = h->pos;			/* bit position of data */
95	hsize = h->report_size;		/* bit length of data */
96
97	if (hsize != 32) {
98		mask = (1 << hsize) - 1;
99		data &= mask;
100	} else
101		mask = ~0;
102
103	data <<= (hpos % 8);
104	mask <<= (hpos % 8);
105	mask = ~mask;
106
107	offs = hpos / 8;
108	end = (hpos + hsize) / 8 - offs;
109
110	for (i = 0; i <= end; i++)
111		buf[offs + i] = (buf[offs + i] & (mask >> (i*8))) |
112		    ((data >> (i*8)) & 0xff);
113}
114