bitstr_t
*
bit_alloc(
int nbits
)
bit_clear(
bit_str name
, int bit
)
bit_decl(
bit_str name
, int nbits
)
bit_ffc(
bit_str name
, int nbits
, int *value
)
bit_ffs(
bit_str name
, int nbits
, int *value
)
bit_nclear(
bit_str name
, int start
, int stop
)
bit_nset(
bit_str name
, int start
, int stop
)
bit_set(
bit_str name
, int bit
)
bitstr_size(
int nbits
)
bit_test(
bit_str name
, int bit
)
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
to
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 <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);
}
}