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BITSTRING(3) | Library Functions 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 macrosSYNOPSIS¶
#include <bsd/bitstring.h> 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 |