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\" @(#)bitstring.3 8.1 (Berkeley) 7/19/93
\"
Dd December 29, 2016
Dt BITSTRING 3
Os
Sh NAME
Nm bit_alloc ,
Nm bit_clear ,
Nm bit_decl ,
Nm bit_ffc ,
Nm bit_ffs ,
Nm bit_nclear ,
Nm bit_nset ,
Nm bit_set ,
Nm bitstr_size ,
Nm bit_test
Nd bit-string manipulation macros
Sh SYNOPSIS
In sys/types.h
In bitstring.h
Ft bitstr_t *
Fn bit_decl "bitstr_t *name" "size_t nbits"
Ft bitstr_t *
Fn bit_alloc "size_t nbits"
Fn bit_clear "bitstr_t *name" "size_t bit"
Fn bit_ffc "const bitstr_t *name" "size_t nbits" "int *value"
Fn bit_ffs "const bitstr_t *name" "size_t nbits" "int *value"
Fn bit_nclear "bitstr_t *name" "size_t start" "size_t stop"
Fn bit_nset "bitstr_t *name" "size_t start" "size_t stop"
Fn bit_set "bitstr_t *name" "size_t bit"
Fn bitstr_size "size_t nbits"
Fn bit_test "const bitstr_t *name" "size_t bit"
Sh DESCRIPTION
These macros operate on strings of bits.
Pp
The macro
Fn bit_alloc
returns a pointer of type
Dq Fa "bitstr_t"
to sufficient space to store
Fa nbits
bits, or
Dv NULL
if no space is available.
Pp
The macro
Fn bit_decl
allocates sufficient space to store
Fa nbits
bits on the stack.
Pp
The macro
Fn 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.
Pp
The macros
Fn bit_clear
and
Fn bit_set
clear or set the zero-based numbered bit
Fa bit ,
in the bit string
Ar name .
Pp
The
Fn bit_nset
and
Fn bit_nclear
macros
set or clear the zero-based numbered bits from
Fa start
to
Fa stop
in the bit string
Ar name .
Pp
The
Fn 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.
Pp
The
Fn 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.
Pp
The macro
Fn 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.
Pp
The arguments to these macros are evaluated only once and may safely
have side effects.
Sh EXAMPLES
Bd -literal -offset indent
#include <limits.h>
#include <bitstring.h>
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);
}
}
Ed
Sh SEE ALSO
Xr bitmap 3 ,
Xr calloc 3 ,
Xr setbit 9
Sh HISTORY
The
Nm bitstring
functions first appeared in
Bx 4.4 .
