180 lines
4.6 KiB
Groff
180 lines
4.6 KiB
Groff
.\" Copyright (c) 1989, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Paul Vixie.
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)bitstring.3 8.1 (Berkeley) 7/19/93
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.\"
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.Dd July 19, 1993
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.Dt BITSTRING 3
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.Os BSD 4
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.Sh NAME
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.Nm bit_alloc ,
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.Nm bit_clear ,
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.Nm bit_decl ,
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.Nm bit_ffs ,
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.Nm bit_nclear ,
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.Nm bit_nset,
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.Nm bit_set ,
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.Nm bitstr_size ,
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.Nm bit_test
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.Nd bit-string manipulation macros
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.Sh SYNOPSIS
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.Fd #include <bitstring.h>
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.Ft bitstr_t *
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.Fn bit_alloc "int nbits"
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.Fn bit_decl "bit_str name" "int nbits"
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.Fn bit_clear "bit_str name" "int bit"
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.Fn bit_ffc "bit_str name" "int nbits" "int *value"
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.Fn bit_ffs "bit_str name" "int nbits" "int *value"
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.Fn bit_nclear "bit_str name" "int start" "int stop"
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.Fn bit_nset "bit_str name" "int start" "int stop"
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.Fn bit_set "bit_str name" "int bit"
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.Fn bitstr_size "int nbits"
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.Fn bit_test "bit_str name" "int bit"
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.Sh DESCRIPTION
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These macros operate on strings of bits.
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.Pp
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The macro
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.Fn bit_alloc
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returns a pointer of type
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.Dq Fa "bitstr_t *"
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to sufficient space to store
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.Fa nbits
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bits, or
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.Dv NULL
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if no space is available.
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.Pp
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The macro
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.Fn bit_decl
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allocates sufficient space to store
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.Fa nbits
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bits on the stack.
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.Pp
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The macro
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.Fn bitstr_size
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returns the number of elements of type
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.Fa bitstr_t
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necessary to store
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.Fa nbits
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bits.
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This is useful for copying bit strings.
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.Pp
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The macros
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.Fn bit_clear
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and
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.Fn bit_set
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clear or set the zero-based numbered bit
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.Fa bit ,
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in the bit string
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.Ar name .
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.Pp
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The
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.Fn bit_nset
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and
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.Fn bit_nclear
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macros
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set or clear the zero-based numbered bits from
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.Fa start
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to
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.Fa stop
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in the bit string
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.Ar name .
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.Pp
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The
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.Fn bit_test
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macro
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evaluates to non-zero if the zero-based numbered bit
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.Fa bit
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of bit string
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.Fa name
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is set, and zero otherwise.
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.Pp
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The
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.Fn bit_ffs
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macro
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stores in the location referenced by
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.Fa value
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the zero-based number of the first bit set in the array of
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.Fa nbits
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bits referenced by
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.Fa name .
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If no bits are set, the location referenced by
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.Fa value
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is set to \-1.
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.Pp
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The macro
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.Fn bit_ffc
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stores in the location referenced by
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.Fa value
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the zero-based number of the first bit not set in the array of
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.Fa nbits
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bits referenced by
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.Fa name .
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If all bits are set, the location referenced by
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.Fa value
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is set to \-1.
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.Pp
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The arguments to these macros are evaluated only once and may safely
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have side effects.
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.Sh EXAMPLE
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.Bd -literal -offset indent
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#include <limits.h>
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#include <bitstring.h>
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...
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#define LPR_BUSY_BIT 0
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#define LPR_FORMAT_BIT 1
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#define LPR_DOWNLOAD_BIT 2
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...
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#define LPR_AVAILABLE_BIT 9
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#define LPR_MAX_BITS 10
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make_lpr_available()
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{
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bitstr_t bit_decl(bitlist, LPR_MAX_BITS);
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...
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bit_nclear(bitlist, 0, LPR_MAX_BITS - 1);
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...
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if (!bit_test(bitlist, LPR_BUSY_BIT)) {
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bit_clear(bitlist, LPR_FORMAT_BIT);
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bit_clear(bitlist, LPR_DOWNLOAD_BIT);
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bit_set(bitlist, LPR_AVAILABLE_BIT);
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}
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}
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.Ed
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.Sh SEE ALSO
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.Xr malloc 3
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.Sh HISTORY
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The
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.Nm bitstring
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functions first appeared in 4.4BSD.
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