1/*	$NetBSD: bitstring.c,v 1.1.1.1 2009/12/13 16:54:14 kardel Exp $	*/
2
3/*
4 * Copyright (C) 2004, 2005, 2007  Internet Systems Consortium, Inc. ("ISC")
5 * Copyright (C) 1999-2001  Internet Software Consortium.
6 *
7 * Permission to use, copy, modify, and/or distribute this software for any
8 * purpose with or without fee is hereby granted, provided that the above
9 * copyright notice and this permission notice appear in all copies.
10 *
11 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
12 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
13 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
14 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
15 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
16 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
17 * PERFORMANCE OF THIS SOFTWARE.
18 */
19
20/* Id: bitstring.c,v 1.17 2007/06/19 23:47:17 tbox Exp */
21
22/*! \file */
23
24#include <config.h>
25
26#include <stddef.h>
27
28#include <isc/magic.h>
29#include <isc/bitstring.h>
30#include <isc/util.h>
31
32#define DIV8(x)			((x) >> 3)
33#define MOD8(x)			((x) & 0x00000007U)
34#define OCTETS(n)		(((n) + 7) >> 3)
35#define PADDED(n)		((((n) + 7) >> 3) << 3)
36#define BITSET(bs, n) 		(((bs)->data[DIV8(n)] & \
37				 (1 << (7 - MOD8(n)))) != 0)
38#define SETBIT(bs, n)		(bs)->data[DIV8(n)] |= (1 << (7 - MOD8(n)))
39#define CLEARBIT(bs, n)		(bs)->data[DIV8(n)] &= ~(1 << (7 - MOD8(n)))
40
41#define BITSTRING_MAGIC		ISC_MAGIC('B', 'S', 't', 'r')
42#define VALID_BITSTRING(b)	ISC_MAGIC_VALID(b, BITSTRING_MAGIC)
43
44void
45isc_bitstring_init(isc_bitstring_t *bitstring, unsigned char *data,
46		   unsigned int length, unsigned int size, isc_boolean_t lsb0)
47{
48	/*
49	 * Make 'bitstring' refer to the bitstring of 'size' bits starting
50	 * at 'data'.  'length' bits of the bitstring are valid.  If 'lsb0'
51	 * is set then, bit 0 refers to the least significant bit of the
52	 * bitstring.  Otherwise bit 0 is the most significant bit.
53	 */
54
55	REQUIRE(bitstring != NULL);
56	REQUIRE(data != NULL);
57	REQUIRE(length <= size);
58
59	bitstring->magic = BITSTRING_MAGIC;
60	bitstring->data = data;
61	bitstring->length = length;
62	bitstring->size = size;
63	bitstring->lsb0 = lsb0;
64}
65
66void
67isc_bitstring_invalidate(isc_bitstring_t *bitstring) {
68
69	/*
70	 * Invalidate 'bitstring'.
71	 */
72
73	REQUIRE(VALID_BITSTRING(bitstring));
74
75	bitstring->magic = 0;
76	bitstring->data = NULL;
77	bitstring->length = 0;
78	bitstring->size = 0;
79	bitstring->lsb0 = ISC_FALSE;
80}
81
82void
83isc_bitstring_copy(isc_bitstring_t *source, unsigned int sbitpos,
84		   isc_bitstring_t *target, unsigned int tbitpos,
85		   unsigned int n)
86{
87	unsigned int tlast;
88
89	/*
90	 * Starting at bit 'sbitpos', copy 'n' bits from 'source' to
91	 * the 'n' bits of 'target' starting at 'tbitpos'.
92	 */
93
94	REQUIRE(VALID_BITSTRING(source));
95	REQUIRE(VALID_BITSTRING(target));
96	REQUIRE(source->lsb0 == target->lsb0);
97	if (source->lsb0) {
98		REQUIRE(sbitpos <= source->length);
99		sbitpos = PADDED(source->size) - sbitpos;
100		REQUIRE(sbitpos >= n);
101		sbitpos -= n;
102	} else
103		REQUIRE(sbitpos + n <= source->length);
104	tlast = tbitpos + n;
105	if (target->lsb0) {
106		REQUIRE(tbitpos <= target->length);
107		tbitpos = PADDED(target->size) - tbitpos;
108		REQUIRE(tbitpos >= n);
109		tbitpos -= n;
110	} else
111		REQUIRE(tlast <= target->size);
112
113	if (tlast > target->length)
114		target->length = tlast;
115
116	/*
117	 * This is far from optimal...
118	 */
119
120	while (n > 0) {
121		if (BITSET(source, sbitpos))
122			SETBIT(target, tbitpos);
123		else
124			CLEARBIT(target, tbitpos);
125		sbitpos++;
126		tbitpos++;
127		n--;
128	}
129}
130