bitstring(3)

NAME

bit_alloc, bit_clear, bit_decl, bit_ffs, bit_nclear,

bit_nset, bit_set,
bitstr_size, bit_test - bit-string manipulation macros

SYNOPSIS

#include <bitstring.h>
bitstr_t *
bit_alloc(int nbits);
void
bit_decl(bitstr_t *name, int nbits);
void
bit_clear(bitstr_t *name, int bit);
void
bit_ffc(bitstr_t *name, int nbits, int *value);
void
bit_ffs(bitstr_t *name, int nbits, int *value);
void
bit_nclear(bitstr_t *name, int start, int stop);
void
bit_nset(bitstr_t *name, int start, int stop);
void
bit_set(bitstr_t *name, int bit);
int
bitstr_size(int nbits);
int
bit_test(bitstr_t *name, int bit);

DESCRIPTION

These macros operate on strings of bits.

The macro bit_alloc() returns a pointer of type ``bitstr_t

*'' to sufficient space to store nbits bits, or NULL if no space is

available.

The macro bit_decl() allocates sufficient space to store

nbits bits on
the stack.

The macro bitstr_size() returns the number of elements of

type bitstr_t
necessary to store nbits bits. This is useful for copying

bit strings.

The macros bit_clear() and bit_set() clear or set the zero

based numbered
bit bit, in the bit string name.

The bit_nset() and bit_nclear() macros set or clear the ze

ro-based numbered bits from start through stop in the bit string name.

The bit_test() macro evaluates to non-zero if the zero-based

numbered bit
bit of bit string name is set, and zero otherwise.

The bit_ffs() macro stores in the location referenced by

value the zerobased 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.

The macro bit_ffc() stores in the location referenced by

value the zerobased 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.

EXAMPLES

#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);

}

}

SEE ALSO

malloc(3)

HISTORY

The bitstring functions first appeared in 4.4BSD.

BSD July 19, 1993

BSD