BITSTRING(3)						   BSD Library Functions Manual 					      BITSTRING(3)

NAME

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

SYNOPSIS

     #include <bitstring.h>

     bitstr_t *
     bit_alloc(int nbits);

     bit_decl(bitstr_t *name, int nbits);

     bit_clear(bitstr_t *name, int bit);

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

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

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

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

     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 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 to 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 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 macro 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 ref-
     erenced by name.  If all bits are set, the location referenced by value is set to -1.

     The macros bit_clear(), bit_set() and bit_test() will evaluate the bit argument more than once, so avoid using pre- or post-, increment or
     decrement.  The arguments to the other macros are evaluated only once and may safely have side effects.

EXAMPLE

	   #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)

HISTORY

     The bitstring functions first appeared in 4.4BSD.

4th Berkeley Distribution					   July 19, 1993					 4th Berkeley Distribution