160 lines
4.4 KiB
C
160 lines
4.4 KiB
C
/* $NetBSD: bitstring.h,v 1.3 2012/06/05 00:42:34 christos Exp $ */
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/*
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* Copyright (C) 2004-2007 Internet Systems Consortium, Inc. ("ISC")
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* Copyright (C) 1999-2001 Internet Software Consortium.
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
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* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
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* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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* OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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* PERFORMANCE OF THIS SOFTWARE.
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*/
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/* Id: bitstring.h,v 1.14 2007/06/19 23:47:18 tbox Exp */
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#ifndef ISC_BITSTRING_H
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#define ISC_BITSTRING_H 1
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/*****
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***** Module Info
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*****/
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/*! \file isc/bitstring.h
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*
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* \brief Bitstring manipulation functions.
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*
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* A bitstring is a packed array of bits, stored in a contiguous
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* sequence of octets. The "most significant bit" (msb) of a bitstring
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* is the high bit of the first octet. The "least significant bit" of a
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* bitstring is the low bit of the last octet.
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*
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* Two bit numbering schemes are supported, "msb0" and "lsb0".
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*
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* In the "msb0" scheme, bit number 0 designates the most significant bit,
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* and any padding bits required to make the bitstring a multiple of 8 bits
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* long are added to the least significant end of the last octet.
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*
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* In the "lsb0" scheme, bit number 0 designates the least significant bit,
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* and any padding bits required to make the bitstring a multiple of 8 bits
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* long are added to the most significant end of the first octet.
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*
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* E.g., consider the bitstring "11010001111". This bitstring is 11 bits
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* long and will take two octets. Let "p" denote a pad bit. In the msb0
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* encoding, it would be
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*
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* \verbatim
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* Octet 0 Octet 1
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* |
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* 1 1 0 1 0 0 0 1 | 1 1 1 p p p p p
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* ^ | ^
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* | |
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* bit 0 bit 15
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* \endverbatim
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*
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* In the lsb0 encoding, it would be
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*
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* \verbatim
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* Octet 0 Octet 1
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* |
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* p p p p p 1 1 0 | 1 0 0 0 1 1 1 1
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* ^ | ^
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* | |
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* bit 15 bit 0
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* \endverbatim
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*/
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/***
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*** Imports
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***/
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#include <isc/lang.h>
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#include <isc/types.h>
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ISC_LANG_BEGINDECLS
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/***
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*** Types
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***/
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struct isc_bitstring {
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unsigned int magic;
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unsigned char * data;
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unsigned int length;
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unsigned int size;
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isc_boolean_t lsb0;
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};
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/***
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*** Functions
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***/
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void
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isc_bitstring_init(isc_bitstring_t *bitstring, unsigned char *data,
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unsigned int length, unsigned int size, isc_boolean_t lsb0);
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/*!<
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* \brief Make 'bitstring' refer to the bitstring of 'size' bits starting
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* at 'data'. 'length' bits of the bitstring are valid. If 'lsb0'
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* is set then, bit 0 refers to the least significant bit of the
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* bitstring. Otherwise bit 0 is the most significant bit.
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*
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* Requires:
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*
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*\li 'bitstring' points to a isc_bitstring_t.
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*
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*\li 'data' points to an array of unsigned char large enough to hold
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* 'size' bits.
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*
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*\li 'length' <= 'size'.
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*
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* Ensures:
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*
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*\li 'bitstring' is a valid bitstring.
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*/
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void
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isc_bitstring_invalidate(isc_bitstring_t *bitstring);
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/*!<
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* \brief Invalidate 'bitstring'.
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*
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* Requires:
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*
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*\li 'bitstring' is a valid bitstring.
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*
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* Ensures:
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*
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*\li 'bitstring' is not a valid bitstring.
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*/
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void
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isc_bitstring_copy(isc_bitstring_t *source, unsigned int sbitpos,
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isc_bitstring_t *target, unsigned int tbitpos,
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unsigned int n);
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/*!<
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* \brief Starting at bit 'sbitpos', copy 'n' bits from 'source' to
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* the 'n' bits of 'target' starting at 'tbitpos'.
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*
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* Requires:
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*
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*\li 'source' and target are valid bitstrings with the same lsb0 setting.
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*
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*\li 'sbitpos' + 'n' is less than or equal to the length of 'source'.
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*
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*\li 'tbitpos' + 'n' is less than or equal to the size of 'target'.
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*
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* Ensures:
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*
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*\li The specified bits have been copied, and the length of 'target'
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* adjusted (if required).
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*/
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ISC_LANG_ENDDECLS
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#endif /* ISC_BITSTRING_H */
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