2 * Copyright (C) 2004-2007 Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (C) 1999-2001 Internet Software Consortium.
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.
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.
18 /* $Id: bitstring.h,v 1.14 2007/06/19 23:47:18 tbox Exp $ */
20 #ifndef ISC_BITSTRING_H
21 #define ISC_BITSTRING_H 1
27 /*! \file isc/bitstring.h
29 * \brief Bitstring manipulation functions.
31 * A bitstring is a packed array of bits, stored in a contiguous
32 * sequence of octets. The "most significant bit" (msb) of a bitstring
33 * is the high bit of the first octet. The "least significant bit" of a
34 * bitstring is the low bit of the last octet.
36 * Two bit numbering schemes are supported, "msb0" and "lsb0".
38 * In the "msb0" scheme, bit number 0 designates the most significant bit,
39 * and any padding bits required to make the bitstring a multiple of 8 bits
40 * long are added to the least significant end of the last octet.
42 * In the "lsb0" scheme, bit number 0 designates the least significant bit,
43 * and any padding bits required to make the bitstring a multiple of 8 bits
44 * long are added to the most significant end of the first octet.
46 * E.g., consider the bitstring "11010001111". This bitstring is 11 bits
47 * long and will take two octets. Let "p" denote a pad bit. In the msb0
48 * encoding, it would be
53 * 1 1 0 1 0 0 0 1 | 1 1 1 p p p p p
59 * In the lsb0 encoding, it would be
64 * p p p p p 1 1 0 | 1 0 0 0 1 1 1 1
76 #include <isc/types.h>
84 struct isc_bitstring {
97 isc_bitstring_init(isc_bitstring_t *bitstring, unsigned char *data,
98 unsigned int length, unsigned int size, isc_boolean_t lsb0);
100 * \brief Make 'bitstring' refer to the bitstring of 'size' bits starting
101 * at 'data'. 'length' bits of the bitstring are valid. If 'lsb0'
102 * is set then, bit 0 refers to the least significant bit of the
103 * bitstring. Otherwise bit 0 is the most significant bit.
107 *\li 'bitstring' points to a isc_bitstring_t.
109 *\li 'data' points to an array of unsigned char large enough to hold
112 *\li 'length' <= 'size'.
116 *\li 'bitstring' is a valid bitstring.
120 isc_bitstring_invalidate(isc_bitstring_t *bitstring);
122 * \brief Invalidate 'bitstring'.
126 *\li 'bitstring' is a valid bitstring.
130 *\li 'bitstring' is not a valid bitstring.
134 isc_bitstring_copy(isc_bitstring_t *source, unsigned int sbitpos,
135 isc_bitstring_t *target, unsigned int tbitpos,
138 * \brief Starting at bit 'sbitpos', copy 'n' bits from 'source' to
139 * the 'n' bits of 'target' starting at 'tbitpos'.
143 *\li 'source' and target are valid bitstrings with the same lsb0 setting.
145 *\li 'sbitpos' + 'n' is less than or equal to the length of 'source'.
147 *\li 'tbitpos' + 'n' is less than or equal to the size of 'target'.
151 *\li The specified bits have been copied, and the length of 'target'
152 * adjusted (if required).
157 #endif /* ISC_BITSTRING_H */