Copyright (c) 1989 The Regents of the University of California.
All rights reserved.

This code is derived from software contributed to Berkeley by
Paul Vixie.

Redistribution and use in source and binary forms are permitted
provided that the above copyright notice and this paragraph are
duplicated in all such forms and that any documentation,
advertising materials, and other materials related to such
distribution and use acknowledge that the software was developed
by the University of California, Berkeley. The name of the
University may not be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

@(#)bitstring.3 5.1 (Berkeley) 12/13/89

C 4 bit_alloc, bit_clear, bit_decl, bit_ffs, bit_nclear, bit_nset, bit_set, bitstr_size, bit_test - bit-string manipulation macros

#include <bitstring.h>

name = bit_alloc(nbits)
bitstr_t *name;
int nbits;

bit_decl(name, nbits)
bitstr_t name;
int nbits;

bit_clear(name, bit)
bitstr_t name;
int bit;

bit_ffc(name, nbits, value)
bitstr_t name;
int nbits, value;

bit_ffs(name, nbits, value)
bitstr_t name;
int nbits, value;

bit_nclear(name, start, stop)
bitstr_t name;
int start, stop;

bit_nset(name, start, stop)
bitstr_t name;
int start, stop;

bit_set(name, bit)
bitstr_t name;
int bit;

bitstr_size(nbits)
int nbits;

bit_test(name, bit)
bitstr_t name;
int bit;

These macros operate on strings of bits.

Bit_alloc returns a pointer of type bitstr_t * to sufficient space to store nbits bits, or NULL if no space is available.

Bit_decl is a macro for allocating sufficient space to store nbits bits on the stack.

Bitstr_size returns the number of elements of type bitstr_t necessary to store nbits bits. This is useful for copying bit strings.

Bit_clear and bit_set clear or set the zero-based numbered bit bit , in the bit string name .

Bit_nset and bit_nclear set or clear the zero-based numbered bits from start to stop in the bit string name .

Bit_test evaluates to zero if the zero-based numbered bit bit of bit string name is set, and non-zero otherwise.

Bit_ffs stores in value the zero-based number of the first bit set in the array of nbits bits referenced by name . If no bits are set, value is set to -1.

Bit_ffc stores in value the zero-based number of the first bit not set in the array of nbits bits referenced by name . If all bits are set, value is set to -1.

The macros bit_nclear , bit_nset , bit_ffc and bit_ffs are fairly complex. It should be noted that they evaluate some of their arguments multiple times. Their arguments should not have side effects.

#include <limits.h>
#include <bitstring.h>

...
#define LPR_BUSY_BIT 0
#define LPR_FORMAT_BIT 1
#define LPR_DOWNLOAD_BIT 2
...
#define LPR_AVAILABLE_BIT 9
#define LPR_MAX_BITS 10

make_lpr_available()
{
 bitstr_t bit_decl(bitlist, LPR_MAX_BITS);
 ...
 bit_nclear(bitlist, 0, LPR_MAX_BITS - 1);
 ...
 if (!bit_test(bitlist, LPR_BUSY_BIT)) {
 bit_clear(bitlist, LPR_FORMAT_BIT);
 bit_clear(bitlist, LPR_DOWNLOAD_BIT);
 bit_set(bitlist, LPR_AVAILABLE_BIT);
 }
}

malloc(3)