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, 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 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 <bitstring.h>
...
#define LPR_BUSY_BIT 0
#define LPR_FORMAT_BIT1
#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
