8907f744ff
Two new functions are provided, bit_ffs_at() and bit_ffc_at(), which allow for efficient searching of set or cleared bits starting from any bit offset within the bit string. Performance is improved by operating on longs instead of bytes and using ffsl() for searches within a long. ffsl() is a compiler builtin in both clang and gcc for most architectures, converting what was a brute force while loop search into a couple of instructions. All of the bitstring(3) API continues to be contained in the header file. Some of the functions are large enough that perhaps they should be uninlined and moved to a library, but that is beyond the scope of this commit. sys/sys/bitstring.h: Convert the majority of the existing bit string implementation from macros to inline functions. Properly protect the implementation from inadvertant macro expansion when included in a user's program by prefixing all private macros/functions and local variables with '_'. Add bit_ffs_at() and bit_ffc_at(). Implement bit_ffs() and bit_ffc() in terms of their "at" counterparts. Provide a kernel implementation of bit_alloc(), making the full API usable in the kernel. Improve code documenation. share/man/man3/bitstring.3: Add pre-exisiting API bit_ffc() to the synopsis. Document new APIs. Document the initialization state of the bit strings allocated/declared by bit_alloc() and bit_decl(). Correct documentation for bitstr_size(). The original code comments indicate the size is in bytes, not "elements of bitstr_t". The new implementation follows this lead. Only hastd assumed "elements" rather than bytes and it has been corrected. etc/mtree/BSD.tests.dist: tests/sys/Makefile: tests/sys/sys/Makefile: tests/sys/sys/bitstring.c: Add tests for all existing and new functionality. include/bitstring.h Include all headers needed by sys/bitstring.h lib/libbluetooth/bluetooth.h: usr.sbin/bluetooth/hccontrol/le.c: Include bitstring.h instead of sys/bitstring.h. sbin/hastd/activemap.c: Correct usage of bitstr_size(). sys/dev/xen/blkback/blkback.c Use new bit_alloc. sys/kern/subr_unit.c: Remove hard-coded assumption that sizeof(bitstr_t) is 1. Get rid of unrb.busy, which caches the number of bits set in unrb.map. When INVARIANTS are disabled, nothing needs to know that information. callapse_unr can be adapted to use bit_ffs and bit_ffc instead. Eliminating unrb.busy saves memory, simplifies the code, and provides a slight speedup when INVARIANTS are disabled. sys/net/flowtable.c: Use the new kernel implementation of bit-alloc, instead of hacking the old libc-dependent macro. sys/sys/param.h Update __FreeBSD_version to indicate availability of new API Submitted by: gibbs, asomers Reviewed by: gibbs, ngie MFC after: 4 weeks Sponsored by: Spectra Logic Corp Differential Revision: https://reviews.freebsd.org/D6004
264 lines
7.2 KiB
Groff
264 lines
7.2 KiB
Groff
.\" Copyright (c) 1989, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to Berkeley by
|
|
.\" Paul Vixie.
|
|
.\" 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
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" Copyright (c) 2014 Spectra Logic Corporation
|
|
.\" 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,
|
|
.\" without modification.
|
|
.\" 2. Redistributions in binary form must reproduce at minimum a disclaimer
|
|
.\" substantially similar to the "NO WARRANTY" disclaimer below
|
|
.\" ("Disclaimer") and any redistribution must be conditioned upon
|
|
.\" including a substantially similar Disclaimer requirement for further
|
|
.\" binary redistribution.
|
|
.\"
|
|
.\" NO WARRANTY
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
.\" "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
|
|
.\" A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
|
|
.\" HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
|
|
.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
|
|
.\" IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
.\" POSSIBILITY OF SUCH DAMAGES.
|
|
.\"
|
|
.\" @(#)bitstring.3 8.1 (Berkeley) 7/19/93
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd May 4, 2016
|
|
.Dt BITSTRING 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm bit_alloc ,
|
|
.Nm bit_clear ,
|
|
.Nm bit_decl ,
|
|
.Nm bit_ffc ,
|
|
.Nm bit_ffs ,
|
|
.Nm bit_ffc_at ,
|
|
.Nm bit_ffs_at ,
|
|
.Nm bit_nclear ,
|
|
.Nm bit_nset ,
|
|
.Nm bit_set ,
|
|
.Nm bit_test ,
|
|
.Nm bitstr_size
|
|
.Nd bit-string manipulation functions and macros
|
|
.Sh SYNOPSIS
|
|
.In bitstring.h
|
|
.Ft bitstr_t *
|
|
.Fn bit_alloc "int nbits"
|
|
.Ft void
|
|
.Fn bit_decl "bitstr_t *name" "int nbits"
|
|
.Ft void
|
|
.Fn bit_clear "bitstr_t *name" "int bit"
|
|
.Ft void
|
|
.Fn bit_ffc "bitstr_t *name" "int nbits" "int *value"
|
|
.Ft void
|
|
.Fn bit_ffs "bitstr_t *name" "int nbits" "int *value"
|
|
.Ft void
|
|
.Fn bit_ffc_at "bitstr_t *name" "int start" "int nbits" "int *value"
|
|
.Ft void
|
|
.Fn bit_ffs_at "bitstr_t *name" "int start" "int nbits" "int *value"
|
|
.Ft void
|
|
.Fn bit_nclear "bitstr_t *name" "int start" "int stop"
|
|
.Ft void
|
|
.Fn bit_nset "bitstr_t *name" "int start" "int stop"
|
|
.Ft void
|
|
.Fn bit_set "bitstr_t *name" "int bit"
|
|
.Ft int
|
|
.Fn bitstr_size "int nbits"
|
|
.Ft int
|
|
.Fn bit_test "bitstr_t *name" "int bit"
|
|
.Sh DESCRIPTION
|
|
These macros operate on strings of bits.
|
|
.Pp
|
|
The function
|
|
.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.
|
|
If successful, the returned bit string is initialized with all bits cleared.
|
|
.Pp
|
|
The macro
|
|
.Fn bit_decl
|
|
declares a bit string with sufficient space to store
|
|
.Fa nbits
|
|
bits.
|
|
.Fn bit_decl
|
|
may be used to include statically sized bit strings in structure
|
|
definitions or to create bit strings on the stack.
|
|
Users of this macro are responsible for initialization of the bit string,
|
|
typically via a global initialization of the containing struct or use of the
|
|
.Fn bit_nset
|
|
or
|
|
.Fn bin_nclear
|
|
functions.
|
|
.Pp
|
|
The macro
|
|
.Fn bitstr_size
|
|
returns the number of bytes necessary to store
|
|
.Fa nbits
|
|
bits.
|
|
This is useful for copying bit strings.
|
|
.Pp
|
|
The functions
|
|
.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
|
|
functions
|
|
set or clear the zero-based numbered bits from
|
|
.Fa start
|
|
through
|
|
.Fa stop
|
|
in the bit string
|
|
.Ar name .
|
|
.Pp
|
|
The
|
|
.Fn bit_test
|
|
function
|
|
evaluates to non-zero if the zero-based numbered bit
|
|
.Fa bit
|
|
of bit string
|
|
.Fa name
|
|
is set, and zero otherwise.
|
|
.Pp
|
|
The function
|
|
.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
|
|
.Fn bit_ffs
|
|
function
|
|
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 function
|
|
.Fn bit_ffc_at
|
|
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 ,
|
|
at or after the zero-based bit index
|
|
.Fa start .
|
|
If all bits at or after
|
|
.Fa start
|
|
are set, the location referenced by
|
|
.Fa value
|
|
is set to \-1.
|
|
.Pp
|
|
The
|
|
.Fn bit_ffs_at
|
|
function
|
|
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 ,
|
|
at or after the zero-based bit index
|
|
.Fa start .
|
|
If no bits are set after
|
|
.Fa start ,
|
|
the location referenced by
|
|
.Fa value
|
|
is set to \-1.
|
|
.Pp
|
|
The arguments in bit string macros are evaluated only once and may safely
|
|
have side effects.
|
|
.Sh EXAMPLES
|
|
.Bd -literal -offset indent
|
|
#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);
|
|
}
|
|
}
|
|
.Ed
|
|
.Sh SEE ALSO
|
|
.Xr malloc 3 ,
|
|
.Xr bitset 9
|
|
.Sh HISTORY
|
|
The
|
|
.Nm bitstring
|
|
functions first appeared in
|
|
.Bx 4.4 .
|