db_access.c revision 879 
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 *	$Id: db_access.c,v 1.3 1993/11/25 01:30:01 wollman Exp $
27 */
28
29/*
30 *	Author: David B. Golub, Carnegie Mellon University
31 *	Date:	7/90
32 */
33#include "param.h"
34#include "systm.h"
35#include "proc.h"
36#include "ddb/ddb.h"
37
38/*
39 * Access unaligned data items on aligned (longword)
40 * boundaries.
41 */
42
43extern void	db_read_bytes();	/* machine-dependent */
44extern void	db_write_bytes();	/* machine-dependent */
45
46unsigned db_extend[] = {	/* table for sign-extending */
47	0,
48	0xFFFFFF80U,
49	0xFFFF8000U,
50	0xFF800000U
51};
52
53db_expr_t
54db_get_value(addr, size, is_signed)
55	db_addr_t	addr;
56	register int	size;
57	boolean_t	is_signed;
58{
59	char		data[sizeof(int)];
60	register db_expr_t value;
61	register int	i;
62
63	db_read_bytes(addr, size, data);
64
65	value = 0;
66#if	BYTE_MSF
67	for (i = 0; i < size; i++)
68#else	/* BYTE_LSF */
69	for (i = size - 1; i >= 0; i--)
70#endif
71	{
72	    value = (value << 8) + (data[i] & 0xFF);
73	}
74
75	if (size < 4) {
76	    if (is_signed && (value & db_extend[size]) != 0)
77		value |= db_extend[size];
78	}
79	return (value);
80}
81
82void
83db_put_value(addr, size, value)
84	db_addr_t	addr;
85	register int	size;
86	register db_expr_t value;
87{
88	char		data[sizeof(int)];
89	register int	i;
90
91#if	BYTE_MSF
92	for (i = size - 1; i >= 0; i--)
93#else	/* BYTE_LSF */
94	for (i = 0; i < size; i++)
95#endif
96	{
97	    data[i] = value & 0xFF;
98	    value >>= 8;
99	}
100
101	db_write_bytes(addr, size, data);
102}
103
104