=pod

=head1 NAME

X509_ALGOR_dup,
X509_ALGOR_set0, X509_ALGOR_get0,
X509_ALGOR_set_md, X509_ALGOR_cmp,
X509_ALGOR_copy - AlgorithmIdentifier functions

=head1 SYNOPSIS

 #include <openssl/x509.h>

 X509_ALGOR *X509_ALGOR_dup(X509_ALGOR *alg);
 int X509_ALGOR_set0(X509_ALGOR *alg, ASN1_OBJECT *aobj, int ptype, void *pval);
 void X509_ALGOR_get0(const ASN1_OBJECT **paobj, int *pptype,
                      const void **ppval, const X509_ALGOR *alg);
 int X509_ALGOR_set_md(X509_ALGOR *alg, const EVP_MD *md);
 int X509_ALGOR_cmp(const X509_ALGOR *a, const X509_ALGOR *b);
 int X509_ALGOR_copy(X509_ALGOR *dest, const X509_ALGOR *src);

=head1 DESCRIPTION

X509_ALGOR_dup() returns a copy of I<alg>.

X509_ALGOR_set0() sets the algorithm OID of I<alg> to I<aobj> and the
associated parameter type to I<ptype> with value I<pval>. If I<ptype> is
B<V_ASN1_UNDEF> the parameter is omitted, otherwise I<ptype> and I<pval> have
the same meaning as the I<type> and I<value> parameters to ASN1_TYPE_set().
All the supplied parameters are used internally so must B<NOT> be freed after
this call succeeded;
otherwise ownership remains with the caller and I<alg> remains untouched.

X509_ALGOR_get0() is the inverse of X509_ALGOR_set0(): it returns the
algorithm OID in I<*paobj> and the associated parameter in I<*pptype>
and I<*ppval> from the B<AlgorithmIdentifier> I<alg>.

X509_ALGOR_set_md() sets the B<AlgorithmIdentifier> I<alg> to appropriate
values for the message digest I<md>.

X509_ALGOR_cmp() compares I<a> and I<b> and returns 0 if they have identical
encodings and nonzero otherwise.

X509_ALGOR_copy() copies the source values into the dest structs; making
a duplicate of each (and free any thing pointed to from within *dest).

=head1 RETURN VALUES

X509_ALGOR_dup() returns a valid B<X509_ALGOR> structure or NULL if an error
occurred.

X509_ALGOR_set0(), X509_ALGOR_set_md(), and X509_ALGOR_copy()
return 1 on success or 0 on error.

X509_ALGOR_get0() returns no values.

X509_ALGOR_cmp() returns 0 if the two parameters have identical encodings and
nonzero otherwise.

=head1 HISTORY

X509_ALGOR_copy() was added in OpenSSL 1.1.1e.

X509_ALGOR_set_md() returns a value since OpenSSL 4.0.

=head1 COPYRIGHT

Copyright 2002-2026 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>.

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