BITSTRING

Section: Misc. Reference Manual Pages (3bsd)
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BSD mandoc

NAME

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

SYNOPSIS

In bitstring.h (See libbsd(7) for include usage.) 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_ffc bitstr_t *name int nbits int *value Ft void Fn bit_ffs bitstr_t *name 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

DESCRIPTION

These macros operate on strings of bits.

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

The macro Fn bit_decl allocates sufficient space to store Fa nbits bits on the stack.

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

The macros Fn bit_clear and Fn bit_set clear or set the zero-based numbered bit Fa bit , in the bit string name

The Fn bit_nset and Fn bit_nclear macros set or clear the zero-based numbered bits from Fa start through Fa stop in the bit string name

The Fn bit_test macro evaluates to non-zero if the zero-based numbered bit Fa bit of bit string Fa name is set, and zero otherwise.

The Fn bit_ffs macro 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.

The macro 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.

The arguments to these macros are evaluated only once and may safely have side effects.

EXAMPLES

#include <limits.h>
#include <bsd/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);
        }
}

HISTORY

The bitstring functions first appeared in BSD 4.4