NAME
bit_alloc, bit_clear, bit_decl, bit_ffs, bit_nclear, bit_nset, bit_set, bitstr_size, bit_test — bit-string manipulation macrosLIBRARY
library “libbsd”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 sufficient space to store nbits bits, orNULL
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 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.July 19, 1993 | Debian |