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/*
* 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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