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BITSTRING(3)             BSD 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 bitstring
     string manipulation macros

SYNOPSIS
     #include <bitstring.h>

     bitstr_t *
     bit_alloc(int nbits);

     bit_decl(bitstr_t *name, int nbits);

     bit_clear(bitstr_t *name, int bit);

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

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

     bit_nclear(bitstr_t *name, int start, int stop);

     bit_nset(bitstr_t *name, int start, int stop);

     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 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 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 macros bit_clear(), bit_set() and bit_test() will evaluate the bit argument more than once, so
     avoid using pre- or post-, increment or decrement.  The arguments to the other 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.

4th Berkeley Distribution        July 19, 1993       4th Berkeley Distribution