=pod

=head1 NAME

X509_ACERT_get_attr,
X509_ACERT_get_attr_by_NID,
X509_ACERT_get_attr_by_OBJ,
X509_ACERT_get_attr_count
- Retrieve attributes from an X509_ACERT structure

=head1 SYNOPSIS

 #include <openssl/x509_acert.h>

 X509_ATTRIBUTE *X509_ACERT_get_attr(const X509_ACERT *x, int loc);
 int X509_ACERT_get_attr_by_NID(const X509_ACERT *x, int nid, int lastpos);
 int X509_ACERT_get_attr_by_OBJ(const X509_ACERT *x, const ASN1_OBJECT *obj,
                                int lastpos);
 int X509_ACERT_get_attr_count(const X509_ACERT *x);

=head1 DESCRIPTION

X509_ACERT_get0_attr() retrieves the I<loc>th B<X509_ATTRIBUTE> from an
B<X509_ACERT> I<x>.  X509_ACERT_get_attr_count() returns the total number
of attributes in the B<X509_ACERT>.

X509_ACERT_get_attr_by_NID() and X509_ACERT_get_attr_by_OBJ() retrieve the next
attribute location matching I<nid> or I<obj> after I<lastpos>. I<lastpos>
should initially be set to -1.
If there are no more entries -1 is returned. If I<nid> is invalid
(doesn't correspond to a valid OID) then -2 is returned.

=head1 RETURN VALUES

X509_ACERT_get0_attr() return a B<X509_ATTRIBUTE> from an attribute
certificate, or NULL if the specified attribute is not found.

X509_ACERT_get_attr_by_NID() and X509_ACERT_get_attr_by_OBJ() return
the location of the next attribute requested or -1 if not found.
X509_ACERT_get_attr_by_NID() can also return -2 if the supplied NID is invalid.

X509_ACERT_get_attr_count() returns the number of attributes in the given
attribute certificate.

=head1 HISTORY

X509_ACERT_get0_attr(), X509_ACERT_get_attr_by_NID(), X509_ACERT_get_attr_by_OBJ() and
X509_ACERT_get_attr_count() were added in OpenSSL 3.4.

=head1 COPYRIGHT

Copyright 2023-2024 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file LICENSE in the source distribution or at
L<https://www.openssl.org/source/license.html>.

=cut