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 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 <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.

Debian                                            July 19, 1993                                  bitstring(3bsd)