bitstring(3) - NetBSD Manual Pages

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BITSTRING(3)            NetBSD Library Functions 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 <sys/types.h>
     #include <bitstring.h>

     bitstr_t *
     bit_decl(bitstr_t *name, size_t nbits);

     bitstr_t *
     bit_alloc(size_t nbits);

     bit_clear(bitstr_t *name, size_t bit);

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

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

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

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

     bit_set(bitstr_t *name, size_t bit);

     bitstr_size(size_t nbits);

     bit_test(const bitstr_t *name, size_t bit);


DESCRIPTION

     These macros operate on strings of bits.

     The macro bit_alloc() returns a pointer of type ``bitstr_t'' to suffi-
     cient 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 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 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 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.


EXAMPLES

           #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

           void
           make_lpr_available(void)
           {
                   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

     bitmap(3), calloc(3), setbit(9)


HISTORY

     The bitstring functions first appeared in 4.4BSD.

NetBSD 8.2                     December 29, 2016                    NetBSD 8.2