.\"	$OpenBSD: ohash_interval.3,v 1.4 2002/05/01 08:03:29 mpech Exp $
.\"
.\" Copyright (c) 2001 Marc Espie.
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.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.