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IN NO EVENT SHALL THE COPYRIGHT .\" HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING .\" IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE .\" POSSIBILITY OF SUCH DAMAGES. .\" .\" @(#)bitstring.3 8.1 (Berkeley) 7/19/93 .\" $FreeBSD$ .\" .Dd May 23, 2016 .Dt BITSTRING 3 .Os .Sh NAME .Nm bit_alloc , .Nm bit_clear , .Nm bit_count , .Nm bit_decl , .Nm bit_ffc , .Nm bit_ffs , .Nm bit_ffc_at , .Nm bit_ffs_at , .Nm bit_nclear , .Nm bit_nset , .Nm bit_set , .Nm bit_test , .Nm bitstr_size .Nd bit-string manipulation functions and macros .Sh SYNOPSIS .In bitstring.h .Ft bitstr_t * .Fn bit_alloc "int nbits" .Ft void .Fn bit_decl "bitstr_t *name" "int nbits" .Ft void .Fn bit_clear "bitstr_t *name" "int bit" .Ft void .Fn bit_count "bitstr_t *name" "int count" "int nbits" "int *value" .Ft void .Fn bit_ffc "bitstr_t *name" "int nbits" "int *value" .Ft void .Fn bit_ffs "bitstr_t *name" "int nbits" "int *value" .Ft void .Fn bit_ffc_at "bitstr_t *name" "int start" "int nbits" "int *value" .Ft void .Fn bit_ffs_at "bitstr_t *name" "int start" "int nbits" "int *value" .Ft void .Fn bit_nclear "bitstr_t *name" "int start" "int stop" .Ft void .Fn bit_nset "bitstr_t *name" "int start" "int stop" .Ft void .Fn bit_set "bitstr_t *name" "int bit" .Ft int .Fn bitstr_size "int nbits" .Ft int .Fn bit_test "bitstr_t *name" "int bit" .Sh DESCRIPTION These macros operate on strings of bits. .Pp The function .Fn bit_alloc returns a pointer of type .Dq Fa "bitstr_t *" to sufficient space to store .Fa nbits bits, or .Dv NULL if no space is available. If successful, the returned bit string is initialized with all bits cleared. .Pp The macro .Fn bit_decl declares a bit string with sufficient space to store .Fa nbits bits. .Fn 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 .Fn bit_nset or .Fn bin_nclear functions. .Pp The macro .Fn bitstr_size returns the number of bytes necessary to store .Fa nbits bits. This is useful for copying bit strings. .Pp The functions .Fn bit_clear and .Fn bit_set clear or set the zero-based numbered bit .Fa bit , in the bit string .Ar name . .Pp The .Fn bit_nset and .Fn bit_nclear functions set or clear the zero-based numbered bits from .Fa start through .Fa stop in the bit string .Ar name . .Pp The .Fn bit_test function evaluates to non-zero if the zero-based numbered bit .Fa bit of bit string .Fa name is set, and zero otherwise. .Pp The function .Fn bit_ffc stores in the location referenced by .Fa value the zero-based number of the first bit not set in the array of .Fa nbits bits referenced by .Fa name . If all bits are set, the location referenced by .Fa value is set to \-1. .Pp The .Fn bit_ffs function stores in the location referenced by .Fa value the zero-based number of the first bit set in the array of .Fa nbits bits referenced by .Fa name . If no bits are set, the location referenced by .Fa value is set to \-1. .Pp The function .Fn bit_ffc_at stores in the location referenced by .Fa value the zero-based number of the first bit not set in the array of .Fa nbits bits referenced by .Fa name , at or after the zero-based bit index .Fa start . If all bits at or after .Fa start are set, the location referenced by .Fa value is set to \-1. .Pp The .Fn bit_ffs_at function stores in the location referenced by .Fa value the zero-based number of the first bit set in the array of .Fa nbits bits referenced by .Fa name , at or after the zero-based bit index .Fa start . If no bits are set after .Fa start , the location referenced by .Fa value is set to \-1. .Pp The .Fn bit_count function stores in the location referenced by .Fa value the number of bits set in the array of .Fa nbits bits referenced by .Fa name , at or after the zero-based bit index .Fa start . .Pp The arguments in bit string macros are evaluated only once and may safely have side effects. .Sh EXAMPLES .Bd -literal -offset indent #include #include \&... #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); } } .Ed .Sh SEE ALSO .Xr malloc 3 , .Xr bitset 9 .Sh HISTORY The .Nm bitstring functions first appeared in .Bx 4.4 .