BITSTRING(3) FreeBSD Library Functions Manual BITSTRING(3)
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
malloc(3), stdbit(3), bitset(9)
HISTORY
The bitstring functions first appeared in 4.4BSD.
FreeBSD 15.1-STABLE-HBSD November 21, 2023 BITSTRING(3)