NAME
bit_alloc,
bit_clear, bit_decl,
bit_ffc, 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);
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);
DESCRIPTION
These macros operate on strings of bits.
The
bit_alloc()
macro returns a pointer of type bitstr_t * to
sufficient space to store nbits bits, or
NULL if no space is available.
The
bit_decl()
macro allocates sufficient space to store nbits bits
on the stack.
The
bitstr_size()
macro returns the number of elements of type bitstr_t
necessary to store nbits bits. This is useful for
copying bit strings.
The
bit_clear()
and
bit_set()
macros clear or set the zero-based numbered bit bit,
in the bit string name.
The
bit_nclear()
and
bit_nset()
macros clear or set 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
bit_ffc()
macro 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 <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
HISTORY
These functions first appeared in 4.3BSD-Reno.