BITSTRING

Section: C Library Functions (3)
Updated: December 13, 1989
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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>

name = bit_alloc(nbits)
bitstr_t *name;
int nbits;

bit_decl(name, nbits)
bitstr_t name;
int nbits;

bit_clear(name, bit)
bitstr_t name;
int bit;

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

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

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

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

bit_set(name, bit)
bitstr_t name;
int bit;

bitstr_size(nbits)
int nbits;

bit_test(name, bit)
bitstr_t name;
int bit;

DESCRIPTION

These macros operate on strings of bits.

Bit_alloc returns a pointer of type bitstr_t * to sufficient space to store nbits bits, or NULL if no space is available.

Bit_decl is a macro for allocating sufficient space to store nbits bits on the stack.

Bitstr_size returns the number of elements of type bitstr_t necessary to store nbits bits. This is useful for copying bit strings.

Bit_clear and bit_set clear or set the zero-based numbered bit bit, in the bit string name.

Bit_nset and bit_nclear set or clear the zero-based numbered bits from start to stop in the bit string name.

Bit_test evaluates to zero if the zero-based numbered bit bit of bit string name is set, and non-zero otherwise.

Bit_ffs sets *value to the zero-based number of the first bit set in the array of nbits bits referenced by name. If no bits are set, *value is set to -1.

Bit_ffc sets *value to the zero-based number of the first bit not set in the array of nbits bits referenced by name. If all bits are set, value is set to -1.

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);
        }
}