Партнёры:
Хостинг:
bit_alloc bit_clear bit_decl bit_ffs bit_nclear bit_nset bit_set bitstr_size bit_test - bit-string manipulation macros
The macro
bit_alloc ();
returns a pointer of type
``Fa bitstr_t *
''
to sufficient space to store
Fa nbits
bits, or
NULL
if no space is available.
The macro
bit_decl ();
allocates sufficient space to store
Fa nbits
bits on the stack.
The macro
bitstr_size ();
returns the number of elements of type
Fa bitstr_t
necessary to store
Fa nbits
bits.
This is useful for copying bit strings.
The macros
bit_clear ();
and
bit_set ();
clear or set the zero-based numbered bit
Fa bit ,
in the bit string
name
The
bit_nset ();
and
bit_nclear ();
macros
set or clear the zero-based numbered bits from
Fa start
through
Fa stop
in the bit string
name
The
bit_test ();
macro
evaluates to non-zero if the zero-based numbered bit
Fa bit
of bit string
Fa name
is set, and zero otherwise.
The
bit_ffs ();
macro
stores in the location referenced by
Fa value
the zero-based number of the first bit set in the array of
Fa nbits
bits referenced by
Fa name .
If no bits are set, the location referenced by
Fa value
is set to -1.
The macro
bit_ffc ();
stores in the location referenced by
Fa value
the zero-based number of the first bit not set in the array of
Fa nbits
bits referenced by
Fa name .
If all bits are set, the location referenced by
Fa value
is set to -1.
The arguments to these macros are evaluated only once and may safely have side effects.
#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);
}
}
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