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.

%sccs.include.redist.man%

@(#)bitstring.3 5.3 (Berkeley) 06/23/90

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

Bit_ffc stores in the location referenced by 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, the location referenced by value is set to -1.

The arguments to these macros are evaluated only once and may safely 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)