BITSTRING(3)              OpenBSD Programmer's Manual             BITSTRING(3)

NAME
     bit_alloc, bit_clear, bit_decl, bit_ffc, bit_ffs, bit_nclear, bit_nset,
     bit_set, bitstr_size, bit_test - bit-string manipulation macros



SYNOPSIS
     #include <bitstring.h>

     bitstr_t *
     bit_alloc(int nbits);

     bit_clear(bit_str name, int bit);

     bit_decl(bit_str name, int nbits);

     bit_ffc(bit_str name, int nbits, int *value);

     bit_ffs(bit_str name, int nbits, int *value);

     bit_nclear(bit_str name, int start, int stop);

     bit_nset(bit_str name, int start, int stop);

     bit_set(bit_str name, int bit);

     bitstr_size(int nbits);

     bit_test(bit_str name, int bit);

DESCRIPTION
     These macros operate on strings of bits.

     The bit_alloc() macro returns a pointer of type bitstr_t * to sufficient
     space to store nbits bits, or NULL if no space is available.

     The bit_decl() macro allocates sufficient space to store nbits bits on
     the stack.

     The bitstr_size() macro returns the number of elements of type bitstr_t
     necessary to store nbits bits.  This is useful for copying bit strings.

     The bit_clear() and bit_set() macros clear or set the zero-based numbered
     bit bit, in the bit string name.

     The bit_nclear() and bit_nset() macros clear or set the zero-based num-
     bered bits from start to 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 bit_ffc() macro 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.

EXAMPLE
           #include <limits.h>
           #include <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.

OpenBSD 2.6                      July 19, 1993                               2