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.\" $OpenBSD: ohash_interval.3,v 1.4 2002/05/01 08:03:29 mpech Exp $
.\"
.\" Copyright (c) 2001 Marc Espie.
.\"
.\" Code written for the OpenBSD project.
.\"
.\" 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.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE OPENBSD PROJECT 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 OPENBSD
.\" PROJECT 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.
.\"
.Dd February 23, 2001
.Dt OPEN_HASH_HELPER 3
.Os
.Sh NAME
.Nm ohash_interval ,
.Nm ohash_create_entry ,
.Nm ohash_qlookup ,
.Nm ohash_qlookupi
.Nd helper functions for open hashing
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <stddef.h>
.Fd #include <ohash.h>
.Ft u_int32_t
.Fn ohash_interval "const char *start" "const char **pend"
.Ft "void *"
.Fn ohash_create_entry "struct ohash_info *info" "const char *start" "const char **pend"
.Ft "unsigned int"
.Fn ohash_qlookupi "struct ohash *h" "const char *start" "const char **pend"
.Ft "unsigned int"
.Fn ohash_qlookup "struct ohash *h" "const char *start"
.Sh DESCRIPTION
These functions are commonly used to simplify open hashing usage, and use
similar conventions.
They operate indifferently on null-terminated strings
.Po
by setting
.Fa *pend
=
.Dv NULL
.Pc
or memory ranges
.Po
deliminated by
.Fa start
and
.Fa *pend
.Pc .
For null-terminated strings, as a side effect, those functions
set
.Fa *pend
to the terminating null byte.
.Pp
.Fn ohash_interval
is a simple hashing function that yields good results on common data sets.
.Pp
.Fn ohash_create_entry
can be used to create a new record with a given key. In that case,
the alloc field of
.Fa info
should point to a
.Xr malloc 3
-like function to allocate the storage.
.Pp
.Fn ohash_qlookupi
is a wrapper function that simply calls
.Fn ohash_interval
and
.Fn ohash_lookup_interval .
.Pp
.Fn ohash_qlookup
is a variation on
.Fn ohash_qlookupi
designed for null-terminated strings.
.Sh SEE ALSO
.Xr ohash_init 3
.Sh STANDARDS
Those functions are completely non-standard and should be avoided in
portable programs.
.Sh HISTORY
Those functions were designed and written for
.Ox
make
by Marc Espie in 1999.
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