xref: /freebsd/share/man/man9/bitset.9 (revision 5546be25d6510ece38fa3f537fd2c6891bd5b3d3)

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.Dd October 20, 2015
.Dt BITSET 9
.Os
.Sh NAME
.Nm bitset(9)
\(em
.Nm BITSET_DEFINE ,
.Nm BITSET_T_INITIALIZER ,
.Nm BITSET_FSET ,
.Nm BIT_CLR ,
.Nm BIT_COPY ,
.Nm BIT_ISSET ,
.Nm BIT_SET ,
.Nm BIT_ZERO ,
.Nm BIT_FILL ,
.Nm BIT_SETOF ,
.Nm BIT_EMPTY ,
.Nm BIT_ISFULLSET ,
.Nm BIT_FFS ,
.Nm BIT_COUNT ,
.Nm BIT_SUBSET ,
.Nm BIT_OVERLAP ,
.Nm BIT_CMP ,
.Nm BIT_OR ,
.Nm BIT_AND ,
.Nm BIT_NAND ,
.Nm BIT_CLR_ATOMIC ,
.Nm BIT_SET_ATOMIC ,
.Nm BIT_SET_ATOMIC_ACQ ,
.Nm BIT_AND_ATOMIC ,
.Nm BIT_OR_ATOMIC ,
.Nm BIT_COPY_STORE_REL
.Nd bitset manipulation macros
.Sh SYNOPSIS
.In sys/_bitset.h
.In sys/bitset.h
.\"
.Fn BITSET_DEFINE "STRUCTNAME" "const SETSIZE"
.Fn BITSET_T_INITIALIZER "ARRAY_CONTENTS"
.Fn BITSET_FSET "N_WORDS"
.\"
.Fn BIT_CLR "const SETSIZE" "size_t bit" "struct STRUCTNAME *bitset"
.Fn BIT_COPY "const SETSIZE" "struct STRUCTNAME *from" "struct STRUCTNAME *to"
.Ft bool
.Fn BIT_ISSET "const SETSIZE" "size_t bit" "struct STRUCTNAME *bitset"
.Fn BIT_SET "const SETSIZE" "size_t bit" "struct STRUCTNAME *bitset"
.Fn BIT_ZERO "const SETSIZE" "struct STRUCTNAME *bitset"
.Fn BIT_FILL "const SETSIZE" "struct STRUCTNAME *bitset"
.Fn BIT_SETOF "const SETSIZE" "size_t bit" "struct STRUCTNAME *bitset"
.Ft bool
.Fn BIT_EMPTY "const SETSIZE" "struct STRUCTNAME *bitset"
.Ft bool
.Fn BIT_ISFULLSET "const SETSIZE" "struct STRUCTNAME *bitset"
.Ft size_t
.Fn BIT_FFS "const SETSIZE" "struct STRUCTNAME *bitset"
.Ft size_t
.Fn BIT_COUNT "const SETSIZE" "struct STRUCTNAME *bitset"
.\"
.Ft bool
.Fo BIT_SUBSET
.Fa "const SETSIZE" "struct STRUCTNAME *haystack" "struct STRUCTNAME *needle"
.Fc
.Ft bool
.Fo BIT_OVERLAP
.Fa "const SETSIZE" "struct STRUCTNAME *bitset1" "struct STRUCTNAME *bitset2"
.Fc
.Ft bool
.Fo BIT_CMP
.Fa "const SETSIZE" "struct STRUCTNAME *bitset1" "struct STRUCTNAME *bitset2"
.Fc
.Fn BIT_OR "const SETSIZE" "struct STRUCTNAME *dst" "struct STRUCTNAME *src"
.Fn BIT_AND "const SETSIZE" "struct STRUCTNAME *dst" "struct STRUCTNAME *src"
.Fn BIT_NAND "const SETSIZE" "struct STRUCTNAME *dst" "struct STRUCTNAME *src"
.\"
.Fn BIT_CLR_ATOMIC "const SETSIZE" "size_t bit" "struct STRUCTNAME *bitset"
.Fn BIT_SET_ATOMIC "const SETSIZE" "size_t bit" "struct STRUCTNAME *bitset"
.Fn BIT_SET_ATOMIC_ACQ "const SETSIZE" "size_t bit" "struct STRUCTNAME *bitset"
.\"
.Fo BIT_AND_ATOMIC
.Fa "const SETSIZE" "struct STRUCTNAME *dst" "struct STRUCTNAME *src"
.Fc
.Fo BIT_OR_ATOMIC
.Fa "const SETSIZE" "struct STRUCTNAME *dst" "struct STRUCTNAME *src"
.Fc
.Fo BIT_COPY_STORE_REL
.Fa "const SETSIZE" "struct STRUCTNAME *from" "struct STRUCTNAME *to"
.Fc
.Sh DESCRIPTION
The
.Nm
family of macros provide a flexible and efficient bitset implementation if the
maximum size of the set is known at compilation.
Throughout this manual page, the name
.Fa SETSIZE
refers to the size of the bitset in bits.
Individual bits in bitsets are referenced with indices zero through
.Fa SETSIZE - 1 .
One example use of
.In sys/bitset.h
is
.In sys/cpuset.h .
.Pp
The
.Fn BITSET_DEFINE
macro defines a bitset struct
.Fa STRUCTNAME
with room to represent
.Fa SETSIZE
bits.
.Pp
The
.Fn BITSET_T_INITIALIZER
macro allows one to initialize a bitset struct with a compile time literal
value.
.Pp
The
.Fn BITSET_FSET
macro generates a compile time literal, usable by
.Fn BITSET_T_INITIALIZER ,
representing a full bitset (all bits set).
For examples of
.Fn BITSET_T_INITIALIZER
and
.Fn BITSET_FSET
usage, see the
.Sx BITSET_T_INITIALIZER EXAMPLE
section.
The
.Fa N_WORDS
parameter to
.Fn BITSET_FSET
should be:
.Bd -literal -offset indent
__bitset_words(SETSIZE)
.Ed
.Pp
The
.Fn BIT_CLR
macro clears bit
.Fa bit
in the bitset pointed to by
.Fa bitset .
The
.Fn BIT_CLR_ATOMIC
macro is identical, but the bit is cleared atomically.
.Pp
The
.Fn BIT_COPY
macro copies the contents of the bitset
.Fa from
to the bitset
.Fa to .
.Fn BIT_COPY_STORE_REL
is similar, but copies component machine words from
.Fa from
and writes them to
.Fa to
with atomic store with release semantics.
(That is, if
.Fa to
is composed of multiple machine words,
.Fn BIT_COPY_STORE_REL
performs multiple individually atomic operations.)
.Pp
The
.Fn BIT_SET
macro sets bit
.Fa bit
in the bitset pointed to by
.Fa bitset .
The
.Fn BIT_SET_ATOMIC
macro is identical, but the bit is set atomically.
The
.Fn BIT_SET_ATOMIC_ACQ
macro sets the bit with acquire semantics.
.Pp
The
.Fn BIT_ZERO
macro clears all bits in
.Fa bitset .
.Pp
The
.Fn BIT_FILL
macro sets all bits in
.Fa bitset .
.Pp
The
.Fn BIT_SETOF
macro clears all bits in
.Fa bitset
before setting only bit
.Fa bit .
.Pp
The
.Fn BIT_EMPTY
macro returns
.Dv true
if
.Fa bitset
is empty.
.Pp
The
.Fn BIT_ISFULLSET
macro returns
.Dv true
if
.Fa bitset
is full (all bits set).
.Pp
The
.Fn BIT_FFS
macro returns the 1-index of the first (lowest) set bit in
.Fa bitset ,
or zero if
.Fa bitset
is empty.
Like with
.Xr ffs 3 ,
to use the non-zero result of
.Fn BIT_FFS
as a
.Fa bit
index parameter to any other
.Nm
macro, you must subtract one from the result.
.Pp
The
.Fn BIT_COUNT
macro returns the total number of set bits in
.Fa bitset .
.Pp
The
.Fn BIT_SUBSET
macro returns
.Dv true
if
.Fa needle
is a subset of
.Fa haystack .
.Pp
The
.Fn BIT_OVERLAP
macro returns
.Dv true
if
.Fa bitset1
and
.Fa bitset2
have any common bits.
(That is, if
.Fa bitset1
AND
.Fa bitset2
is not the empty set.)
.Pp
The
.Fn BIT_CMP
macro returns
.Dv true
if
.Fa bitset1
is NOT equal to
.Fa bitset2 .
.Pp
The
.Fn BIT_OR
macro sets bits present in
.Fa src
in
.Fa dst .
(It is the
.Nm
equivalent of the scalar:
.Fa dst
|=
.Fa src . )
.Fn BIT_OR_ATOMIC
is similar, but sets bits in the component machine words in
.Fa dst
atomically.
(That is, if
.Fa dst
is composed of multiple machine words,
.Fn BIT_OR_ATOMIC
performs multiple individually atomic operations.)
.Pp
The
.Fn BIT_AND
macro clears bits absent from
.Fa src
from
.Fa dst .
(It is the
.Nm
equivalent of the scalar:
.Fa dst
&=
.Fa src . )
.Fn BIT_AND_ATOMIC
is similar, with the same atomic semantics as
.Fn BIT_OR_ATOMIC .
.Pp
The
.Fn BIT_NAND
macro clears bits set in
.Fa src
from
.Fa dst .
(It is the
.Nm
equivalent of the scalar:
.Fa dst
&=
.Fa ~ src . )
.Sh BITSET_T_INITIALIZER EXAMPLE
.Bd -literal
BITSET_DEFINE(_myset, MYSETSIZE);

struct _myset myset;

/* Initialize myset to filled (all bits set) */
myset = BITSET_T_INITIALIZER(BITSET_FSET(__bitset_words(MYSETSIZE)));

/* Initialize myset to only the lowest bit set */
myset = BITSET_T_INITIALIZER(0x1);
.Ed
.Sh SEE ALSO
.Xr bitstring 3 ,
.Xr cpuset 9
.Sh HISTORY
The
.Nm
macros first appeared in
.Fx 10.0
in January 2014.
They were MFCed to
.Fx 9.3 ,
released in July 2014.
.Pp
This manual page first appeared in
.Fx 11.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm
macros were generalized and pulled out of
.In sys/cpuset.h
as
.In sys/_bitset.h
and
.In sys/bitset.h
by
.An Attilio Rao Aq Mt attilio@FreeBSD.org .
This manual page was written by
.An Conrad Meyer Aq Mt cem@FreeBSD.org .
.Sh CAVEATS
The
.Fa SETSIZE
argument to all of these macros must match the value given to
.Fn BITSET_DEFINE .
.Pp
Unlike every other reference to individual set members, which are zero-indexed,
.Fn BIT_FFS
returns a one-indexed result (or zero if the set is empty).