BITSTRING(3)

NAME
bit_alloc, bit_clear, bit_decl, bit_ffs, bit_fls, bit_nclear, bit_nset, bit_nsearch, bit_set, bitstr_size, bit_test - bit-string manipulation 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_ffc(bitstr_t *name, int nbits, int *value);
void
bit_ffs(bitstr_t *name, int nbits, int *value);
void
bit_fls(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_nsearch(bitstr_t *name, int nbits, int *value, int len);
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 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 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 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 referenced by name. If all bits are set, the location referenced by value is set to -1.

The macro bit_fls() stores in the location referenced by value the zero-based number of the highest bit set in array of nbits bits referenced by name.

The macro bit_nsearch() stores in the location referenced by value the zero-based index of a span of clear bits of length len in the array of nbits bits referenced by name.

The arguments to these 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)

HISTORY
The bitstring functions first appeared in 4.4BSD. The bit_fls() and bit_nsearch() routines first appeared in DragonFly 2.9.