db_access.c revision 21673 
1/*
2 * Mach Operating System
3 * Copyright (c) 1991,1990 Carnegie Mellon University
4 * All Rights Reserved.
5 *
6 * Permission to use, copy, modify and distribute this software and its
7 * documentation is hereby granted, provided that both the copyright
8 * notice and this permission notice appear in all copies of the
9 * software, derivative works or modified versions, and any portions
10 * thereof, and that both notices appear in supporting documentation.
11 *
12 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS
13 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
14 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
15 *
16 * Carnegie Mellon requests users of this software to return to
17 *
18 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
19 *  School of Computer Science
20 *  Carnegie Mellon University
21 *  Pittsburgh PA 15213-3890
22 *
23 * any improvements or extensions that they make and grant Carnegie the
24 * rights to redistribute these changes.
25 *
26 *	$FreeBSD: head/sys/ddb/db_access.c 21673 1997-01-14 07:20:47Z jkh $
27 */
28
29/*
30 *	Author: David B. Golub, Carnegie Mellon University
31 *	Date:	7/90
32 */
33#include <sys/param.h>
34#include <sys/systm.h>
35
36#include <ddb/ddb.h>
37#include <ddb/db_access.h>
38
39/*
40 * Access unaligned data items on aligned (longword)
41 * boundaries.
42 */
43
44static unsigned db_extend[] = {	/* table for sign-extending */
45	0,
46	0xFFFFFF80U,
47	0xFFFF8000U,
48	0xFF800000U
49};
50
51db_expr_t
52db_get_value(addr, size, is_signed)
53	db_addr_t	addr;
54	register int	size;
55	boolean_t	is_signed;
56{
57	char		data[sizeof(int)];
58	register db_expr_t value;
59	register int	i;
60
61	db_read_bytes(addr, size, data);
62
63	value = 0;
64#if	BYTE_MSF
65	for (i = 0; i < size; i++)
66#else	/* BYTE_LSF */
67	for (i = size - 1; i >= 0; i--)
68#endif
69	{
70	    value = (value << 8) + (data[i] & 0xFF);
71	}
72
73	if (size < 4) {
74	    if (is_signed && (value & db_extend[size]) != 0)
75		value |= db_extend[size];
76	}
77	return (value);
78}
79
80void
81db_put_value(addr, size, value)
82	db_addr_t	addr;
83	register int	size;
84	register db_expr_t value;
85{
86	char		data[sizeof(int)];
87	register int	i;
88
89#if	BYTE_MSF
90	for (i = size - 1; i >= 0; i--)
91#else	/* BYTE_LSF */
92	for (i = 0; i < size; i++)
93#endif
94	{
95	    data[i] = value & 0xFF;
96	    value >>= 8;
97	}
98
99	db_write_bytes(addr, size, data);
100}
101
102