BITSTRING(3) MachTen Programmer’s 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(bit_str name, int nbits)

bit_clear(bit_str name, int bit)

bit_ffc(bit_str name, int nbits, int *value)

bit_ffs(bit_str name, int nbits, int *value)

bit_nclear(bit_str name, int start, int stop)

bit_nset(bit_str name, int start, int stop)

bit_set(bit_str name, int bit)

bitstr_size(int nbits)

bit_test(bit_str name, int bit)

DESCRIPTION
These macros operate on strings of bits.

The macro bit_alloc() returns a pointer of type ‘‘bitstr_t *’’ to suffi-
cient 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 num-
bered 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 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 refer-
enced 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.

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);
}
}