1 /* $NetBSD: bitstring.h,v 1.1.1.1 2009/12/13 16:54:25 kardel Exp $ */ 2 3 /* 4 * Copyright (C) 2004-2007 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.h,v 1.14 2007/06/19 23:47:18 tbox Exp */ 21 22 #ifndef ISC_BITSTRING_H 23 #define ISC_BITSTRING_H 1 24 25 /***** 26 ***** Module Info 27 *****/ 28 29 /*! \file isc/bitstring.h 30 * 31 * \brief Bitstring manipulation functions. 32 * 33 * A bitstring is a packed array of bits, stored in a contiguous 34 * sequence of octets. The "most significant bit" (msb) of a bitstring 35 * is the high bit of the first octet. The "least significant bit" of a 36 * bitstring is the low bit of the last octet. 37 * 38 * Two bit numbering schemes are supported, "msb0" and "lsb0". 39 * 40 * In the "msb0" scheme, bit number 0 designates the most significant bit, 41 * and any padding bits required to make the bitstring a multiple of 8 bits 42 * long are added to the least significant end of the last octet. 43 * 44 * In the "lsb0" scheme, bit number 0 designates the least significant bit, 45 * and any padding bits required to make the bitstring a multiple of 8 bits 46 * long are added to the most significant end of the first octet. 47 * 48 * E.g., consider the bitstring "11010001111". This bitstring is 11 bits 49 * long and will take two octets. Let "p" denote a pad bit. In the msb0 50 * encoding, it would be 51 * 52 * \verbatim 53 * Octet 0 Octet 1 54 * | 55 * 1 1 0 1 0 0 0 1 | 1 1 1 p p p p p 56 * ^ | ^ 57 * | | 58 * bit 0 bit 15 59 * \endverbatim 60 * 61 * In the lsb0 encoding, it would be 62 * 63 * \verbatim 64 * Octet 0 Octet 1 65 * | 66 * p p p p p 1 1 0 | 1 0 0 0 1 1 1 1 67 * ^ | ^ 68 * | | 69 * bit 15 bit 0 70 * \endverbatim 71 */ 72 73 /*** 74 *** Imports 75 ***/ 76 77 #include <isc/lang.h> 78 #include <isc/types.h> 79 80 ISC_LANG_BEGINDECLS 81 82 /*** 83 *** Types 84 ***/ 85 86 struct isc_bitstring { 87 unsigned int magic; 88 unsigned char * data; 89 unsigned int length; 90 unsigned int size; 91 isc_boolean_t lsb0; 92 }; 93 94 /*** 95 *** Functions 96 ***/ 97 98 void 99 isc_bitstring_init(isc_bitstring_t *bitstring, unsigned char *data, 100 unsigned int length, unsigned int size, isc_boolean_t lsb0); 101 /*!< 102 * \brief Make 'bitstring' refer to the bitstring of 'size' bits starting 103 * at 'data'. 'length' bits of the bitstring are valid. If 'lsb0' 104 * is set then, bit 0 refers to the least significant bit of the 105 * bitstring. Otherwise bit 0 is the most significant bit. 106 * 107 * Requires: 108 * 109 *\li 'bitstring' points to a isc_bitstring_t. 110 * 111 *\li 'data' points to an array of unsigned char large enough to hold 112 * 'size' bits. 113 * 114 *\li 'length' <= 'size'. 115 * 116 * Ensures: 117 * 118 *\li 'bitstring' is a valid bitstring. 119 */ 120 121 void 122 isc_bitstring_invalidate(isc_bitstring_t *bitstring); 123 /*!< 124 * \brief Invalidate 'bitstring'. 125 * 126 * Requires: 127 * 128 *\li 'bitstring' is a valid bitstring. 129 * 130 * Ensures: 131 * 132 *\li 'bitstring' is not a valid bitstring. 133 */ 134 135 void 136 isc_bitstring_copy(isc_bitstring_t *source, unsigned int sbitpos, 137 isc_bitstring_t *target, unsigned int tbitpos, 138 unsigned int n); 139 /*!< 140 * \brief Starting at bit 'sbitpos', copy 'n' bits from 'source' to 141 * the 'n' bits of 'target' starting at 'tbitpos'. 142 * 143 * Requires: 144 * 145 *\li 'source' and target are valid bitstrings with the same lsb0 setting. 146 * 147 *\li 'sbitpos' + 'n' is less than or equal to the length of 'source'. 148 * 149 *\li 'tbitpos' + 'n' is less than or equal to the size of 'target'. 150 * 151 * Ensures: 152 * 153 *\li The specified bits have been copied, and the length of 'target' 154 * adjusted (if required). 155 */ 156 157 ISC_LANG_ENDDECLS 158 159 #endif /* ISC_BITSTRING_H */ 160