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