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BITSTRING(3)	       FreeBSD Library Functions Manual		  BITSTRING(3)

NAME
     bit_alloc,	bit_clear, bit_count, bit_decl,	bit_ffc, bit_ffs, bit_ffc_at,
     bit_ffs_at, bit_nclear, bit_nset, bit_set,	bit_test, bitstr_size -- bit-
     string manipulation functions and macros

SYNOPSIS
     #include <bitstring.h>

     bitstr_t *
     bit_alloc(int nbits);

     void
     bit_decl(bitstr_t *name, int nbits);

     void
     bit_clear(bitstr_t	*name, int bit);

     void
     bit_count(bitstr_t	*name, int count, int nbits, int *value);

     void
     bit_ffc(bitstr_t *name, int nbits,	int *value);

     void
     bit_ffs(bitstr_t *name, int nbits,	int *value);

     void
     bit_ffc_at(bitstr_t *name,	int start, int nbits, int *value);

     void
     bit_ffs_at(bitstr_t *name,	int start, int nbits, int *value);

     void
     bit_nclear(bitstr_t *name,	int start, int stop);

     void
     bit_nset(bitstr_t *name, int start, int stop);

     void
     bit_set(bitstr_t *name, int bit);

     int
     bitstr_size(int nbits);

     int
     bit_test(bitstr_t *name, int bit);

DESCRIPTION
     These macros operate on strings of	bits.

     The function bit_alloc() returns a	pointer	of type	``bitstr_t *'' to suf-
     ficient 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 num-
     bered 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 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 refer-
     enced 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 refer-
     enced 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_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 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),	bitset(9)

HISTORY
     The bitstring functions first appeared in 4.4BSD.

FreeBSD	11.1			 May 23, 2016			  FreeBSD 11.1

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | HISTORY

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