169 lines
3.3 KiB
Groff
169 lines
3.3 KiB
Groff
.\" Copyright (c) 1989 The Regents of the University of California.
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.\" 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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.\"
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.\" Redistribution and use in source and binary forms are permitted
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.\" provided that the above copyright notice and this paragraph are
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.\" duplicated in all such forms and that any documentation,
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.\" advertising materials, and other materials related to such
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.\" distribution and use acknowledge that the software was developed
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.\" by the University of California, Berkeley. The name of the
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.\" University may not be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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.\"
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.\" @(#)bitstring.3 5.1 (Berkeley) 12/13/89
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.\"
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.TH BITSTRING 3 "December 13, 1989"
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.UC 4
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.SH NAME
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bit_alloc, bit_clear, bit_decl, bit_ffs, bit_nclear, bit_nset,
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bit_set, bitstr_size, bit_test \- bit-string manipulation macros
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.SH SYNOPSIS
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.ft B
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.nf
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#include <bitstring.h>
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name = bit_alloc(nbits)
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bitstr_t *name;
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int nbits;
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bit_decl(name, nbits)
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bitstr_t name;
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int nbits;
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bit_clear(name, bit)
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bitstr_t name;
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int bit;
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bit_ffc(name, nbits, value)
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bitstr_t name;
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int nbits, *value;
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bit_ffs(name, nbits, value)
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bitstr_t name;
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int nbits, *value;
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bit_nclear(name, start, stop)
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bitstr_t name;
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int start, stop;
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bit_nset(name, start, stop)
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bitstr_t name;
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int start, stop;
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bit_set(name, bit)
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bitstr_t name;
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int bit;
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bitstr_size(nbits)
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int nbits;
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bit_test(name, bit)
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bitstr_t name;
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int bit;
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.fi
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.ft R
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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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.I Bit_alloc
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returns a pointer of type
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.I bitstr_t\ *
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to sufficient space to store
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.I nbits
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bits, or NULL if no space is available.
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.PP
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.I Bit_decl
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is a macro for allocating sufficient space to store
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.I nbits
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bits on the stack.
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.PP
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.I Bitstr_size
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returns the number of elements of type
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.I bitstr_t
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necessary to store
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.I 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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.I Bit_clear
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and
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.I bit_set
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clear or set the zero-based numbered bit
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.IR bit ,
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in the bit string
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.IR name .
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.PP
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.I Bit_nset
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and
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.I bit_nclear
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set or clear the zero-based numbered bits from
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.I start
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to
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.I stop
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in the bit string
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.IR name .
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.PP
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.I Bit_test
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evaluates to zero if the zero-based numbered bit
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.I bit
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of bit string
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.I name
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is set, and non-zero otherwise.
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.PP
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.I Bit_ffs
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sets
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.I *value
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to the zero-based number of the first bit set in the array of
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.I nbits
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bits referenced by
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.IR name .
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If no bits are set,
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.I *value
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is set to -1.
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.PP
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.I Bit_ffc
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sets
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.I *value
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to the zero-based number of the first bit not set in the array of
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.I nbits
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bits referenced by
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.IR name .
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If all bits are set,
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.I value
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is set to -1.
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.SH EXAMPLE
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.nf
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.in +5
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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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.fi
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.SH "SEE ALSO"
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malloc(3)
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