NAME
bit_alloc,
bit_clear, bit_count,
bit_decl, bit_ffc,
bit_ffs, bit_ff_at,
bit_ffc_at, bit_ffs_at,
bit_ffc_area, bit_ffs_area,
bit_ff_area_at,
bit_ffc_area_at,
bit_ffs_area_at, bit_nclear,
bit_nset, bit_ntest,
bit_set, bit_test,
bitstr_size —
bit-string manipulation functions and
macros
SYNOPSIS
#include
<bitstring.h>
bitstr_t *
bit_alloc(size_t
nbits);
void
bit_decl(bitstr_t
*name, size_t
nbits);
void
bit_clear(bitstr_t
*name, size_t
bit);
void
bit_count(bitstr_t
*name, size_t
count, size_t
nbits, ssize_t
*value);
void
bit_ffc(bitstr_t
*name, size_t
nbits, ssize_t
*value);
void
bit_ffs(bitstr_t
*name, size_t
nbits, ssize_t
*value);
void
bit_ffc_at(bitstr_t
*name, size_t
start, size_t
nbits, ssize_t
*value);
void
bit_ffs_at(bitstr_t
*name, size_t
start, size_t
nbits, ssize_t
*value);
void
bit_ff_at(bitstr_t
*name, size_t
start, size_t
nbits, int match,
ssize_t *value);
void
bit_ffc_area(bitstr_t
*name, size_t
nbits, size_t size,
ssize_t *value);
void
bit_ffs_area(bitstr_t
*name, size_t
nbits, size_t size,
ssize_t *value);
void
bit_ffc_area_at(bitstr_t
*name, size_t
start, size_t
nbits, size_t size,
ssize_t *value);
void
bit_ffs_area_at(bitstr_t
*name, size_t
start, size_t
nbits, size_t size,
ssize_t *value);
void
bit_ff_area_at(bitstr_t
*name, size_t
start, size_t
nbits, size_t size,
int match,
ssize_t *value);
bit_foreach(bitstr_t
*name, size_t
nbits, size_t
var);
bit_foreach_at(bitstr_t
*name, size_t
start, size_t
nbits, size_t
var);
bit_foreach_unset(bitstr_t
*name, size_t
nbits, size_t
var);
bit_foreach_unset_at(bitstr_t
*name, size_t
start, size_t
nbits, size_t
var);
void
bit_nclear(bitstr_t
*name, size_t
start, size_t
stop);
void
bit_nset(bitstr_t
*name, size_t
start, size_t
stop);
int
bit_ntest(bitstr_t
*name, size_t
start, size_t stop,
int match);
void
bit_set(bitstr_t
*name, size_t
bit);
int
bitstr_size(size_t
nbits);
int
bit_test(bitstr_t
*name, size_t
bit);
DESCRIPTION
These macros operate on strings of bits.
The function
bit_alloc()
returns a pointer of type “bitstr_t *”
to sufficient space to store nbits bits, or
NULL if no space is available. If successful, the
returned bit string is initialized with all bits cleared.
The macro
bit_decl()
declares a bit string with sufficient space to store
nbits bits. bit_decl() may be
used to include statically sized bit strings in structure definitions or to
create bit strings on the stack. Users of this macro are responsible for
initialization of the bit string, typically via a global initialization of
the containing struct or use of the bit_nset() or
bin_nclear()
functions.
The macro
bitstr_size()
returns the number of bytes necessary to store nbits
bits. This is useful for copying bit strings.
The functions
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()
functions set or clear the zero-based numbered bits from
start through stop in the bit
string name.
The
bit_test()
function evaluates to non-zero if the zero-based numbered bit
bit of bit string name is set,
and zero otherwise.
The
bit_ntest()
function evaluates to non-zero if the zero-based numbered bits from
start through stop in the bit
string name all have the value
match.
The function
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
bit_ffs()
function 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 function
bit_ffc_at()
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,
at or after the zero-based bit index start. If all
bits at or after start are set, the location
referenced by value is set to -1.
The
bit_ffs_at()
function 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,
at or after the zero-based bit index start. If no bits
are set after start, the location referenced by
value is set to -1.
The
bit_ff_at()
function stores in the location referenced by value
the zero-based number of the first bit in the array of
nbits bits referenced by name,
at or after the zero-based bit index start that has
value match. If no bits after
start match that value, the location referenced by
value is set to -1.
The
bit_ffc_area()
function stores in the location referenced by value
the zero-based number of the first bit beginning a sequence of unset bits of
at least size unset bits in the array of
nbits bits referenced by name.
If no sequence of contiguous unset bits of the specified
size can be found, the location referenced by
value is set to -1.
The
bit_ffs_area()
function stores in the location referenced by value
the zero-based number of the first bit beginning a sequence of set bits of
at least size set bits in the array of
nbits bits referenced by name.
If no sequence of contiguous set bits of the specified
size can be found, the location referenced by
value is set to -1.
The
bit_ffc_area_at()
function stores in the location referenced by value
the zero-based number of the first bit beginning a sequence of unset bits of
at least size unset bits in the array of
nbits bits referenced by name,
at or after the zero-based bit index start. If no
sequence of contiguous unset bits of the specified
size can be found at or after
start, the location referenced by
value is set to -1.
The
bit_ffs_area_at()
function stores in the location referenced by value
the zero-based number of the first bit beginning a sequence of set bits of
at least size set bits in the array of
nbits bits referenced by name,
at or after the zero-based bit index start. If no
sequence of contiguous set bits of the specified size
can be found at or after start, the location
referenced by value is set to -1.
The
bit_ff_area_at()
function stores in the location referenced by value
the zero-based number of the first bit beginning a sequence of bits of at
least size bits in the array of
nbits bits referenced by name,
at or after the zero-based bit index start in which
all bits have the value match. If no sequence of
contiguous such bits of the specified size can be
found at or after start, the location referenced by
value is set to -1.
The
bit_count()
function stores in the location referenced by value
the number of bits set in the array of nbits bits
referenced by name, at or after the zero-based bit
index start.
The macro
bit_foreach()
traverses all set bits in the array of nbits
referenced by name in the forward direction, assigning
each location in turn to var.
The macro
bit_foreach_at()
traverses all set bits in the array of nbits
referenced by name in the forward direction at or
after the zero-based bit index start, assigning each
location in turn to var.
The macro
bit_foreach_unset()
traverses all unset bits in the array of nbits
referenced by name in the forward direction, assigning
each location in turn to var.
The macro
bit_foreach_unset_at()
traverses all unset bits in the array of nbits
referenced by name in the forward direction at or
after the zero-based bit index start, assigning each
location in turn to var.
The arguments in bit string 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
The bitstring functions first appeared in
4.4BSD.