.\" $OpenBSD: a2d_ASN1_OBJECT.3,v 1.2 2022/01/01 02:06:07 jsg Exp $
.\"
.\" Copyright (c) 2021 Ingo Schwarze <schwarze@openbsd.org>
.\"
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.Dd $Mdocdate: January 1 2022 $
.Dt A2D_ASN1_OBJECT 3
.Os
.Sh NAME
.Nm a2d_ASN1_OBJECT
.Nd DER content octets of an ASN.1 object identifier
.Sh SYNOPSIS
.Ft int
.Fo a2d_ASN1_OBJECT
.Fa "unsigned char *der_out"
.Fa "int olen"
.Fa "const char *val_in"
.Fa "int ilen"
.Fc
.Sh DESCRIPTION
.Fn a2d_ASN1_OBJECT
accepts an ASCII string
.Fa val_in
of
.Fa ilen
bytes and interprets it as the numerical form of an ASN.1 object identifier.
It writes the content octets of the DER encoding of the object identifier
to the buffer
.Fa der_out
which is
.Fa olen
bytes long.
The identifier and length octets of the DER encoding are not written.
.Pp
If
.Fa ilen
is \-1, the
.Xr strlen 3
of
.Fa val_in
is used instead.
.Pp
If
.Fa der_out
is a
.Dv NULL
pointer, writing the content objects is skipped
and only the return value is calculated.
.Sh RETURN VALUES
.Fn a2d_ASN1_OBJECT
returns the number of content octets that were or would be written or 0 if
.Fa ilen
is 0, if
.Fa val_in
is not a valid representation of an object identifier,
if memory allocation fails, or if the number of content octets
would be larger than
.Fa olen .
.Sh SEE ALSO
.Xr ASN1_OBJECT_new 3 ,
.Xr i2d_ASN1_OBJECT 3 ,
.Xr OBJ_create 3
.Sh STANDARDS
ITU-T Recommendation X.690, also known as ISO/IEC 8825-1:
Information technology - ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical Encoding
Rules (CER) and Distinguished Encoding Rules (DER),
section 8.19: Encoding of an object identifier value
.Sh HISTORY
.Fn a2d_ASN1_OBJECT
first appeared in SSLeay 0.8.0 and has been available since
.Ox 2.4 .