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.\" $OpenBSD: ohash_interval.3,v 1.1 2014/05/12 19:09:00 espie Exp $
.\" Copyright (c) 2001 Marc Espie <espie@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: May 12 2014 $
.Dt OHASH_INTERVAL 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
.In stdint.h
.In stddef.h
.In ohash.h
.Ft uint32_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 NUL-terminated strings
.Po
by setting
.Fa *pend
=
.Dv NULL
.Pc
or memory ranges
.Po
delimited by
.Fa start
and
.Fa *pend
.Pc .
For NUL-terminated strings, as a side effect, those functions
set
.Fa *pend
to the terminating NUL 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 Ns -like
function to allocate the storage:
.Bd -literal -offset indent
p = (*info->alloc)(sz, info->data);
.Ed
.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 NUL-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
.Xr make 1
by Marc Espie in 1999.
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