bitstring(3bsd) LOCAL bitstring(3bsd)
NAME
bit_alloc, bit_clear, bit_decl, bit_ffs, bit_nclear, bit_nset, bit_set,
bitstr_size, bit_test — bit-string manipulation macros
LIBRARY
Utility functions from BSD systems (libbsd, -lbsd)
SYNOPSIS
#include <bitstring.h>
(See libbsd(7) for include usage.)
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_nclear(bitstr_t *name, int start, int stop);
void
bit_nset(bitstr_t *name, int start, int stop);
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 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 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 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.
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);
}
}
SEE ALSO
malloc(3)
HISTORY
The bitstring functions first appeared in 4.4BSD.
BSD July 19, 1993 BSD
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