Edit File: bitstring.h
/* * Copyright (C) 2004-2007 Internet Systems Consortium, Inc. ("ISC") * Copyright (C) 1999-2001 Internet Software Consortium. * * Permission to use, copy, modify, and/or distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR * PERFORMANCE OF THIS SOFTWARE. */ /* $Id: bitstring.h,v 1.14 2007-06-19 23:47:18 tbox Exp $ */ #ifndef ISC_BITSTRING_H #define ISC_BITSTRING_H 1 /***** ***** Module Info *****/ /*! \file isc/bitstring.h * * \brief Bitstring manipulation functions. * * A bitstring is a packed array of bits, stored in a contiguous * sequence of octets. The "most significant bit" (msb) of a bitstring * is the high bit of the first octet. The "least significant bit" of a * bitstring is the low bit of the last octet. * * Two bit numbering schemes are supported, "msb0" and "lsb0". * * In the "msb0" scheme, bit number 0 designates the most significant bit, * and any padding bits required to make the bitstring a multiple of 8 bits * long are added to the least significant end of the last octet. * * In the "lsb0" scheme, bit number 0 designates the least significant bit, * and any padding bits required to make the bitstring a multiple of 8 bits * long are added to the most significant end of the first octet. * * E.g., consider the bitstring "11010001111". This bitstring is 11 bits * long and will take two octets. Let "p" denote a pad bit. In the msb0 * encoding, it would be * * \verbatim * Octet 0 Octet 1 * | * 1 1 0 1 0 0 0 1 | 1 1 1 p p p p p * ^ | ^ * | | * bit 0 bit 15 * \endverbatim * * In the lsb0 encoding, it would be * * \verbatim * Octet 0 Octet 1 * | * p p p p p 1 1 0 | 1 0 0 0 1 1 1 1 * ^ | ^ * | | * bit 15 bit 0 * \endverbatim */ /*** *** Imports ***/ #include <isc/lang.h> #include <isc/types.h> ISC_LANG_BEGINDECLS /*** *** Types ***/ struct isc_bitstring { unsigned int magic; unsigned char * data; unsigned int length; unsigned int size; isc_boolean_t lsb0; }; /*** *** Functions ***/ void isc_bitstring_init(isc_bitstring_t *bitstring, unsigned char *data, unsigned int length, unsigned int size, isc_boolean_t lsb0); /*!< * \brief Make 'bitstring' refer to the bitstring of 'size' bits starting * at 'data'. 'length' bits of the bitstring are valid. If 'lsb0' * is set then, bit 0 refers to the least significant bit of the * bitstring. Otherwise bit 0 is the most significant bit. * * Requires: * *\li 'bitstring' points to a isc_bitstring_t. * *\li 'data' points to an array of unsigned char large enough to hold * 'size' bits. * *\li 'length' <= 'size'. * * Ensures: * *\li 'bitstring' is a valid bitstring. */ void isc_bitstring_invalidate(isc_bitstring_t *bitstring); /*!< * \brief Invalidate 'bitstring'. * * Requires: * *\li 'bitstring' is a valid bitstring. * * Ensures: * *\li 'bitstring' is not a valid bitstring. */ void isc_bitstring_copy(isc_bitstring_t *source, unsigned int sbitpos, isc_bitstring_t *target, unsigned int tbitpos, unsigned int n); /*!< * \brief Starting at bit 'sbitpos', copy 'n' bits from 'source' to * the 'n' bits of 'target' starting at 'tbitpos'. * * Requires: * *\li 'source' and target are valid bitstrings with the same lsb0 setting. * *\li 'sbitpos' + 'n' is less than or equal to the length of 'source'. * *\li 'tbitpos' + 'n' is less than or equal to the size of 'target'. * * Ensures: * *\li The specified bits have been copied, and the length of 'target' * adjusted (if required). */ ISC_LANG_ENDDECLS #endif /* ISC_BITSTRING_H */
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