.\" $OpenBSD: ober_oid_cmp.3,v 1.4 2021/03/12 07:24:49 jsg Exp $
.\"
.\" Copyright (c) 2007, 2012 Reyk Floeter <reyk@openbsd.org>
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.Dd $Mdocdate: March 12 2021 $
.Dt OBER_OID_CMP 3
.Os
.Sh NAME
.Nm ober_oid_cmp ,
.Nm ober_oid2ber ,
.Nm ober_string2oid
.Nd OID helper functions for the BER library
.Sh SYNOPSIS
.In sys/types.h
.In ber.h
.Ft "int"
.Fn "ober_oid_cmp" "struct ber_oid *a" "struct ber_oid *b"
.Ft "size_t"
.Fn "ober_oid2ber" "struct ber_oid *oid" "u_int8_t *buf" "size_t size"
.Ft "int"
.Fn "ober_string2oid" "const char *string" "struct ber_oid *oid"
.Sh DESCRIPTION
Object Identifiers are commonly used in ASN.1-based protocols.
These functions provide an interface to parse OIDs.
For internal representation of OIDs, the following structure
.Vt struct ber_oid
is being used:
.Bd -literal
#define BER_MIN_OID_LEN		2
#define BER_MAX_OID_LEN		64

struct ber_oid {
	u_int32_t	bo_id[BER_MAX_OID_LEN + 1];
	size_t		bo_n;
};
.Ed
.Pp
The
.Fn ober_oid2ber
and
.Fn ober_string2oid
functions may be used to convert from and to
.Vt struct ber_oid .
.Pp
.Fn ober_oid_cmp
may be used to compare two
.Vt ber_oid
structures.
.Sh RETURN VALUES
.Fn ober_oid2ber
returns the number of bytes written or 0 on failure.
.Pp
.Fn ober_string2oid
returns 0 on success or -1 on failure.
.Pp
.Fn ober_oid_cmp
returns 0 when oids
.Fa a
and
.Fa b
are identical.
If
.Fa b
is a successor of
.Fa a ,
1 is returned.
If
.Fa b
is a predecessor of
.Fa a ,
-1 is returned.
If
.Fa b
is larger, but a child of
.Fa a ,
2 is returned.
.Sh SEE ALSO
.Xr ober_add_string 3 ,
.Xr ober_get_string 3 ,
.Xr ober_read_elements 3 ,
.Xr ober_set_header 3
.Sh HISTORY
These functions first appeared as internal functions in
.Xr snmpd 8
in
.Ox 4.2
and were moved to libutil in
.Ox 6.6 .
.Sh AUTHORS
.An -nosplit
The BER library was written by
.An Claudio Jeker Aq Mt claudio@openbsd.org ,
.An Marc Balmer Aq Mt marc@openbsd.org
and
.An Reyk Floeter Aq Mt reyk@openbsd.org .