| bitstring(3bsd) | 3bsd | bitstring(3bsd) |
bit_alloc,
bit_clear, bit_decl,
bit_ffs, bit_nclear,
bit_nset, bit_set,
bitstr_size, bit_test
— bit-string manipulation macros
library “libbsd”
#include
<bitstring.h> (See
libbsd(7) for include usage.)
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);
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 zero-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
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.
The macro
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 <bsd/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);
}
}
The bitstring functions first appeared in
4.4BSD.
| July 19, 1993 | Debian |