NAME    [Toc]    [Back]

     bit_alloc, bit_clear, bit_decl, bit_ffs, bit_nclear, bit_nset, bit_set,
     bitstr_size, bit_test -- bit-string manipulation macros

SYNOPSIS    [Toc]    [Back]

     #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_ffc(bitstr_t *name, int nbits, int *value);

     void
     bit_ffs(bitstr_t *name, 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    [Toc]    [Back]

     These macros operate on strings of bits.

     The macro bit_alloc() returns a pointer of type ``bitstr_t *'' to sufficient
 space to store nbits bits, or NULL if no space is available.

     The macro bit_decl() allocates sufficient space to store nbits bits on
     the stack.

     The macro bitstr_size() returns the number of elements of type bitstr_t
     necessary to store nbits bits.  This is useful for copying bit strings.

     The macros 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() macros set or clear the zero-based numbered
 bits from start through 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 zerobased
 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 macro bit_ffc() stores in the location referenced by value the zerobased
 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    [Toc]    [Back]

	   #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    [Toc]    [Back]

     malloc(3)

HISTORY    [Toc]    [Back]

     The bitstring functions first appeared in 4.4BSD.


FreeBSD 5.2.1			 July 19, 1993			 FreeBSD 5.2.1