52e8f6a331
Add bit_ffs_area_at and bit_ffc_area_at functions for searching a bit string for a sequence of contiguous set or unset bits of at least the specified size. The bit_ffc_area function will be used by the Intel ice driver for implementing resource assignment logic using a bitstring to represent whether or not a given index has been assigned or is currently free. The bit_ffs_area, bit_ffc_area_at and bit_ffs_area_at functions are implemented for completeness. I'd like to add further test cases for the new functions, but I'm not really sure how to add them easily. The new functions depend on specific sequences of bits being set, while the bitstring tests appear to run for varying bit sizes. Signed-off-by: Jacob Keller <jacob.e.keller@intel.com> Submitted by: Jacob Keller <jacob.e.keller@intel.com> Reviewed by: asomers@, erj@ MFC after: 1 week Sponsored by: Intel Corporation Differential Revision: https://reviews.freebsd.org/D22400
366 lines
9.5 KiB
Groff
366 lines
9.5 KiB
Groff
.\" Copyright (c) 1989, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Paul Vixie.
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" Copyright (c) 2014,2016 Spectra Logic Corporation
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions, and the following disclaimer,
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.\" without modification.
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.\" 2. Redistributions in binary form must reproduce at minimum a disclaimer
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.\" substantially similar to the "NO WARRANTY" disclaimer below
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.\" ("Disclaimer") and any redistribution must be conditioned upon
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.\" including a substantially similar Disclaimer requirement for further
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.\" binary redistribution.
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.\"
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.\" NO WARRANTY
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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.\" "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
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.\" A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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.\" HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
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.\" IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGES.
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.\"
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.\" @(#)bitstring.3 8.1 (Berkeley) 7/19/93
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.\" $FreeBSD$
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.\"
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.Dd Nov 18, 2019
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.Dt BITSTRING 3
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.Os
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.Sh NAME
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.Nm bit_alloc ,
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.Nm bit_clear ,
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.Nm bit_count ,
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.Nm bit_decl ,
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.Nm bit_ffc ,
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.Nm bit_ffs ,
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.Nm bit_ffc_at ,
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.Nm bit_ffs_at ,
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.Nm bit_ffc_area ,
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.Nm bit_ffs_area ,
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.Nm bit_ffc_area_at ,
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.Nm bit_ffs_area_at ,
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.Nm bit_nclear ,
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.Nm bit_nset ,
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.Nm bit_set ,
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.Nm bit_test ,
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.Nm bitstr_size
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.Nd bit-string manipulation functions and macros
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.Sh SYNOPSIS
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.In bitstring.h
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.Ft bitstr_t *
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.Fn bit_alloc "int nbits"
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.Ft void
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.Fn bit_decl "bitstr_t *name" "int nbits"
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.Ft void
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.Fn bit_clear "bitstr_t *name" "int bit"
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.Ft void
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.Fn bit_count "bitstr_t *name" "int count" "int nbits" "int *value"
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.Ft void
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.Fn bit_ffc "bitstr_t *name" "int nbits" "int *value"
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.Ft void
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.Fn bit_ffs "bitstr_t *name" "int nbits" "int *value"
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.Ft void
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.Fn bit_ffc_at "bitstr_t *name" "int start" "int nbits" "int *value"
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.Ft void
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.Fn bit_ffs_at "bitstr_t *name" "int start" "int nbits" "int *value"
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.Ft void
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.Fn bit_ffc_area "bitstr_t *name" "int nbits" "int size" "int *value"
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.Ft void
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.Fn bit_ffs_area "bitstr_t *name" "int nbits" "int size" "int *value"
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.Ft void
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.Fn bit_ffc_area_at "bitstr_t *name" "int start" "int nbits" "int size" "int *value"
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.Ft void
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.Fn bit_ffs_area_at "bitstr_t *name" "int start" "int nbits" "int size" "int *value"
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.Ft void
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.Fn bit_nclear "bitstr_t *name" "int start" "int stop"
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.Ft void
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.Fn bit_nset "bitstr_t *name" "int start" "int stop"
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.Ft void
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.Fn bit_set "bitstr_t *name" "int bit"
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.Ft int
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.Fn bitstr_size "int nbits"
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.Ft int
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.Fn bit_test "bitstr_t *name" "int bit"
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.Sh DESCRIPTION
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These macros operate on strings of bits.
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.Pp
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The function
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.Fn bit_alloc
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returns a pointer of type
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.Dq Fa "bitstr_t *"
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to sufficient space to store
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.Fa nbits
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bits, or
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.Dv NULL
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if no space is available.
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If successful, the returned bit string is initialized with all bits cleared.
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.Pp
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The macro
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.Fn bit_decl
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declares a bit string with sufficient space to store
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.Fa nbits
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bits.
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.Fn bit_decl
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may be used to include statically sized bit strings in structure
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definitions or to create bit strings on the stack.
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Users of this macro are responsible for initialization of the bit string,
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typically via a global initialization of the containing struct or use of the
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.Fn bit_nset
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or
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.Fn bin_nclear
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functions.
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.Pp
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The macro
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.Fn bitstr_size
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returns the number of bytes necessary to store
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.Fa nbits
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bits.
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This is useful for copying bit strings.
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.Pp
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The functions
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.Fn bit_clear
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and
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.Fn bit_set
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clear or set the zero-based numbered bit
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.Fa bit ,
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in the bit string
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.Ar name .
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.Pp
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The
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.Fn bit_nset
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and
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.Fn bit_nclear
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functions
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set or clear the zero-based numbered bits from
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.Fa start
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through
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.Fa stop
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in the bit string
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.Ar name .
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.Pp
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The
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.Fn bit_test
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function
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evaluates to non-zero if the zero-based numbered bit
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.Fa bit
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of bit string
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.Fa name
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is set, and zero otherwise.
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.Pp
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The function
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.Fn bit_ffc
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stores in the location referenced by
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.Fa value
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the zero-based number of the first bit not set in the array of
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.Fa nbits
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bits referenced by
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.Fa name .
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If all bits are set, the location referenced by
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.Fa value
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is set to \-1.
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.Pp
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The
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.Fn bit_ffs
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function
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stores in the location referenced by
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.Fa value
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the zero-based number of the first bit set in the array of
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.Fa nbits
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bits referenced by
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.Fa name .
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If no bits are set, the location referenced by
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.Fa value
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is set to \-1.
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.Pp
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The function
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.Fn bit_ffc_at
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stores in the location referenced by
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.Fa value
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the zero-based number of the first bit not set in the array of
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.Fa nbits
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bits referenced by
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.Fa name ,
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at or after the zero-based bit index
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.Fa start .
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If all bits at or after
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.Fa start
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are set, the location referenced by
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.Fa value
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is set to \-1.
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.Pp
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The
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.Fn bit_ffs_at
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function
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stores in the location referenced by
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.Fa value
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the zero-based number of the first bit set in the array of
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.Fa nbits
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bits referenced by
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.Fa name ,
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at or after the zero-based bit index
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.Fa start .
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If no bits are set after
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.Fa start ,
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the location referenced by
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.Fa value
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is set to \-1.
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.Pp
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The
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.Fn bit_ffc_area
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function stores in the location referenced by
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.Fa value
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the zero-based number of the first bit beginning a sequence of unset bits of
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at least
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.Fa size
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unset bits in the array of
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.Fa nbits
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bits referenced by
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.Fa name .
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If no sequence of contiguous unset bits of the specified
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.Fa size
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can be found, the location referenced by
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.Fa value
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is set to \-1.
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.Pp
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The
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.Fn bit_ffs_area
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function stores in the location referenced by
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.Fa value
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the zero-based number of the first bit beginning a sequence of set bits of
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at least
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.Fa size
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set bits in the array of
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.Fa nbits
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bits referenced by
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.Fa name .
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If no sequence of contiguous set bits of the specified
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.Fa size
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can be found, the location referenced by
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.Fa value
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is set to \-1.
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.Pp
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The
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.Fn bit_ffc_area_at
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function stores in the location referenced by
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.Fa value
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the zero-based number of the first bit beginning a sequence of unset bits of
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at least
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.Fa size
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unset bits in the array of
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.Fa nbits
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bits referenced by
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.Fa name ,
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at or after the zero-based bit index
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.Fa start .
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If no sequence of contiguous unset bits of the specified
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.Fa size
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can be found at or after
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.Fa start ,
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the location referenced by
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.Fa value
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is set to \-1.
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.Pp
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The
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.Fn bit_ffs_area_at
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function stores in the location referenced by
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.Fa value
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the zero-based number of the first bit beginning a sequence of set bits of
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at least
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.Fa size
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set bits in the array of
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.Fa nbits
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bits referenced by
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.Fa name ,
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at or after the zero-based bit index
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.Fa start .
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If no sequence of contiguous set bits of the specified
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.Fa size
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can be found at or after
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.Fa start ,
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the location referenced by
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.Fa value
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is set to \-1.
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.Pp
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The
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.Fn bit_count
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function stores in the location referenced by
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.Fa value
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the number of bits set in the array of
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.Fa nbits
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bits referenced by
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.Fa name ,
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at or after the zero-based bit index
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.Fa start .
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.Pp
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The arguments in bit string macros are evaluated only once and may safely
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have side effects.
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.Sh EXAMPLES
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.Bd -literal -offset indent
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#include <limits.h>
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#include <bitstring.h>
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\&...
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#define LPR_BUSY_BIT 0
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#define LPR_FORMAT_BIT 1
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#define LPR_DOWNLOAD_BIT 2
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\&...
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#define LPR_AVAILABLE_BIT 9
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#define LPR_MAX_BITS 10
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make_lpr_available()
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{
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bitstr_t bit_decl(bitlist, LPR_MAX_BITS);
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...
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bit_nclear(bitlist, 0, LPR_MAX_BITS - 1);
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...
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if (!bit_test(bitlist, LPR_BUSY_BIT)) {
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bit_clear(bitlist, LPR_FORMAT_BIT);
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bit_clear(bitlist, LPR_DOWNLOAD_BIT);
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bit_set(bitlist, LPR_AVAILABLE_BIT);
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}
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}
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.Ed
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.Sh SEE ALSO
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.Xr malloc 3 ,
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.Xr bitset 9
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.Sh HISTORY
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The
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.Nm bitstring
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functions first appeared in
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.Bx 4.4 .
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