BIT_EMPTY (9)

Leading comments

Copyright (c) 2015 Conrad Meyer <cem@FreeBSD.org>
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   document...

(The comments found at the beginning of the groff file "man9/BIT_EMPTY.9freebsd".)

NAME

bitset(9) --- BITSET_DEFINE BITSET_T_INITIALIZER BITSET_FSET BIT_CLR BIT_COPY BIT_ISSET BIT_SET BIT_ZERO BIT_FILL BIT_SETOF BIT_EMPTY BIT_ISFULLSET BIT_FFS BIT_COUNT BIT_SUBSET BIT_OVERLAP BIT_CMP BIT_OR BIT_AND BIT_NAND BIT_CLR_ATOMIC BIT_SET_ATOMIC BIT_SET_ATOMIC_ACQ BIT_AND_ATOMIC BIT_OR_ATOMIC BIT_COPY_STORE_REL - bitset manipulation macros

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 int Fn BIT_FFS const SETSIZE struct STRUCTNAME *bitset Ft int 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

DESCRIPTION

The 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 .

The Fn BITSET_DEFINE macro defines a bitset struct Fa STRUCTNAME with room to represent Fa SETSIZE bits.

The Fn BITSET_T_INITIALIZER macro allows one to initialize a bitset struct with a compile time literal value.

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:

__bitset_words(SETSIZE)

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.

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.)

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.

The Fn BIT_ZERO macro clears all bits in Fa bitset .

The Fn BIT_FILL macro sets all bits in Fa bitset .

The Fn BIT_SETOF macro clears all bits in Fa bitset before setting only bit Fa bit .

The Fn BIT_EMPTY macro returns true if Fa bitset is empty.

The Fn BIT_ISFULLSET macro returns true if Fa bitset is full (all bits set).

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 ffs(3), to use the non-zero result of Fn BIT_FFS as a Fa bit index parameter to any other macro, you must subtract one from the result.

The Fn BIT_COUNT macro returns the total number of set bits in Fa bitset .

The Fn BIT_SUBSET macro returns true if Fa needle is a subset of Fa haystack .

The Fn BIT_OVERLAP macro returns true if Fa bitset1 and Fa bitset2 have any common bits. (That is, if Fa bitset1 AND Fa bitset2 is not the empty set.)

The Fn BIT_CMP macro returns true if Fa bitset1 is NOT equal to Fa bitset2 .

The Fn BIT_OR macro sets bits present in Fa src in Fa dst . (It is the 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.)

The Fn BIT_AND macro clears bits absent from Fa src from Fa dst . (It is the equivalent of the scalar: Fa dst &= Fa src . ) Fn BIT_AND_ATOMIC is similar, with the same atomic semantics as Fn BIT_OR_ATOMIC .

The Fn BIT_NAND macro clears bits set in Fa src from Fa dst . (It is the equivalent of the scalar: Fa dst &= Fa ~ src . )

BITSET_T_INITIALIZER EXAMPLE

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);

SEE ALSO

bitstring(3), cpuset(9)

HISTORY

The macros first appeared in Fx 10.0 in January 2014. They were MFCed to Fx 9.3 , released in July 2014.

This manual page first appeared in Fx 11.0 .

AUTHORS

An -nosplit The 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 .

CAVEATS

The Fa SETSIZE argument to all of these macros must match the value given to Fn BITSET_DEFINE .

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).