2003-04-16 17:34:34 +04:00
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.\" $NetBSD: hash.9,v 1.3 2003/04/16 13:35:28 wiz Exp $
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2001-12-05 10:31:24 +03:00
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.\"
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.\" Copyright (c) 2001 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Luke Mewburn of Wasabi Systems, Inc.
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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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.\" 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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd December 5, 2001
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.Dt HASH 9
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.Os
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.Sh NAME
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.Nm hash ,
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.Nm hash32_buf ,
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.Nm hash32_str ,
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.Nm hash32_strn
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.Nd kernel hash functions
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.Sh SYNOPSIS
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2003-04-16 17:34:34 +04:00
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.In sys/types.h
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.In sys/hash.h
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2001-12-05 10:31:24 +03:00
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.Ft uint32_t
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.Fn hash32_buf "const void *buf" "size_t len" "uint32_t ihash"
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.Ft uint32_t
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.Fn hash32_str "const void *buf" "uint32_t ihash"
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.Ft uint32_t
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.Fn hash32_strn "const void *buf" "size_t len" "uint32_t ihash"
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.Sh DESCRIPTION
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The
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.Nm
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functions returns a hash of the given buffer.
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.Pp
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The
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.Fn hash32_buf
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function returns a 32 bit hash of
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.Fa buf ,
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which is
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.Fa len
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bytes long,
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seeded with an initial hash of
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.Fa ihash
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(which is usually
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.Dv HASH32_BUF_INIT ) .
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This function may use a different algorithm to
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.Fn hash32_str
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and
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.Fn hash32_strn .
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.Pp
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The
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.Fn hash32_str
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function returns a 32 bit hash of
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.Fa buf ,
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which is
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a
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.Dv NUL
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terminated
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.Tn ASCII
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string,
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seeded with an initial hash of
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.Fa ihash
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(which is usually
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.Dv HASH32_STR_INIT ) .
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This function must use the same algorithm as
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.Fn hash32_strn ,
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so that the same data returns the same hash.
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.Pp
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The
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.Fn hash32_strn
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function returns a 32 bit hash of
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.Fa buf ,
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which is
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a
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.Dv NUL
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terminated
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.Tn ASCII
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string,
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up to a maximum of
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.Fa len
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bytes,
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seeded with an initial hash of
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.Fa ihash
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(which is usually
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.Dv HASH32_STR_INIT ) .
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This function must use the same algorithm as
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.Fn hash32_str ,
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so that the same data returns the same hash.
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.Pp
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The
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.Fa ihash
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parameter is provided to allow for incremental hashing by allowing
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successive calls to use a previous hash value.
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.Sh RETURN VALUES
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The
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.Fa hash32_*
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functions return a 32 bit hash of the provided buffer.
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.Sh HISTORY
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The kernel hashing API first appeared in
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.Nx 1.6 .
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