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.\" $OpenBSD: ASN1_item_new.3,v 1.4 2018/03/22 21:08:22 schwarze Exp $
.\"
.\" Copyright (c) 2016, 2018 Ingo Schwarze <schwarze@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: March 22 2018 $
.Dt ASN1_ITEM_NEW 3
.Os
.Sh NAME
.Nm ASN1_item_new ,
.Nm ASN1_item_free
.Nd generic ASN.1 value constructor and destructor
.Sh SYNOPSIS
.In openssl/asn1.h
.Ft ASN1_VALUE *
.Fo ASN1_item_new
.Fa "const ASN1_ITEM *it"
.Fc
.Ft void
.Fo ASN1_item_free
.Fa "ASN1_VALUE *val_in"
.Fa "const ASN1_ITEM *it"
.Fc
.Sh DESCRIPTION
.Fn ASN1_item_new
allocates and initializes an empty ASN.1 value
of the type described by the global static object
.Fa it .
.Pp
If the item type described by
.Fa it
is reference counted,
.Fn ASN1_item_free
decrements the reference count of
.Fa val_in .
Otherwise, or if the reference count reaches 0,
.Fn ASN1_item_free
frees
.Fa val_in ,
assuming that it is of the type described by
.Fa it .
If the true type of
.Fa val_in
fails to match the specified
.Fa it ,
buffer overflows and segmentation faults are likely to occur.
It is not possible to recover the type of an
.Vt ASN1_VALUE
object by inspecting it; the type always needs to be remembered
separately.
.Pp
.Vt ASN1_VALUE
is an incomplete type, and pointers to it always require casting
to the correct complete type before they can be dereferenced.
For all practical purposes, a pointer to
.Vt ASN1_VALUE
is equivalent to a
.Vt void
pointer.
.Pp
Depending on
.Fa it ,
there are more than 150 different types that
.Fn ASN1_item_new
may return.
Most of them are pointers to structures or pointers to arrays of
structures, but there are a few exceptions, for example:
If
.Fa it
is
.Dv ASN1_NULL_it ,
.Fn ASN1_item_new
returns a specific invalid pointer representing the unique
.Vt ASN1_NULL
object.
If
.Fa it
is
.Dv ASN1_BOOLEAN_it
or
.Dv LONG_it ,
.Fn ASN1_item_new
does not return a pointer at all, but a
.Vt long
value cast to
.Vt ASN1_VALUE * .
.Sh RETURN VALUES
.Fn ASN1_item_new
returns the new
.Vt ASN1_VALUE
object or
.Dv NULL
if an error occurs.
.Sh SEE ALSO
.Xr ASN1_item_d2i 3 ,
.Xr ASN1_TYPE_new 3 ,
.Xr d2i_ASN1_NULL 3 ,
.Xr OBJ_nid2obj 3
.Sh HISTORY
.Fn ASN1_item_new
and
.Fn ASN1_item_free
first appeared in OpenSSL 0.9.7 and have been available since
.Ox 3.2 .
.Sh BUGS
The
.Vt ASN1_VALUE
type compromises type safety and invites programming mistakes that
will typically have severe consequences.
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