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
<bsd/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
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.
EXAMPLES¶
#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);
}
}
SEE ALSO¶
malloc(3)
HISTORY¶
The
bitstring functions first appeared in
4.4BSD.
