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.Dd $Mdocdate: September 12 2022 $
.Dt D2I_ASN1_OBJECT 3
.Os
.Sh NAME
.Nm d2i_ASN1_OBJECT ,
.Nm i2d_ASN1_OBJECT
.Nd decode and encode ASN.1 object identifiers
.Sh SYNOPSIS
.In openssl/asn1.h
.Ft ASN1_OBJECT *
.Fo d2i_ASN1_OBJECT
.Fa "ASN1_OBJECT **val_out"
.Fa "unsigned char **der_in"
.Fa "long length"
.Fc
.Ft int
.Fo i2d_ASN1_OBJECT
.Fa "const ASN1_OBJECT *val_in"
.Fa "unsigned char **der_out"
.Fc
.Sh DESCRIPTION
These functions decode and encode ASN.1 object identifiers.
For details about the semantics, examples, caveats, and bugs, see
.Xr ASN1_item_d2i 3 .
.Pp
The LibreSSL implementation of
.Fn d2i_ASN1_OBJECT
always calls
.Xr ASN1_OBJECT_free 3
if an existing object is passed in via
.Fa val_out
and it always creates a new object from scratch.
Other implementations may attempt to reuse an existing object,
which is fragile and prone to bugs.
Consequently, always passing
.Dv NULL
for the
.Fa val_out
argument is recommended.
.Pp
The objects returned from
.Fn d2i_ASN1_OBJECT
and the data contained in them are always marked as dynamically
allocated, so when they are no longer needed,
.Xr ASN1_OBJECT_free 3
can be called on them.
.Sh RETURN VALUES
.Fn d2i_ASN1_OBJECT
returns a pointer to the new
.Vt ASN1_OBJECT
object or
.Dv NULL
if an error occurs.
With other implementations, it might return a pointer to the reused
.Vt ASN1_OBJECT .
.Pp
.Fn i2d_ASN1_OBJECT
returns the number of bytes successfully encoded
or a value <= 0 if an error occurs.
.Sh SEE ALSO
.Xr a2d_ASN1_OBJECT 3 ,
.Xr ASN1_item_d2i 3 ,
.Xr ASN1_OBJECT_new 3 ,
.Xr OBJ_nid2obj 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 d2i_ASN1_OBJECT
and
.Fn i2d_ASN1_OBJECT
first appeared in SSLeay 0.5.1 and have been available since
.Ox 2.4 .
.Sh CAVEATS
.Fn d2i_ASN1_OBJECT
never sets the long and short names of the object, not even if the
object identifier matches one that is built into the library.
To find the names of an object identifier parsed from DER or BER
input, call
.Xr OBJ_obj2nid 3
on the returned object, and then
.Xr OBJ_nid2sn 3
and
.Xr OBJ_nid2ln 3
on the result.