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Man Pages


Manual Reference Pages  -  BITSTR_SIZE (3)

NAME

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

CONTENTS

Synopsis
Description
Examples
See Also
History

SYNOPSIS


.In bitstring.h 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 <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 BSD 4.4 .
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