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BITSTRING (3) | C library functions | Unix Manual Pages | :man

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_BIT1
#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


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