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=head1 NAME

d2i_X509_ALGOR, i2d_X509_ALGOR, X509_ALGOR_dup, X509_ALGOR_set0, X509_ALGOR_get0, X509_ALGOR_set_md, X509_ALGOR_cmp - AlgorithmIdentifier functions.

=head1 SYNOPSIS

 #include <openssl/x509.h>

 X509_ALGOR *d2i_X509_ALGOR(X509_ALGOR **a, unsigned char **pp, long length);
 int i2d_X509_ALGOR(X509_ALGOR *a, unsigned char **pp);
 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(ASN1_OBJECT **paobj, int *pptype, void **ppval,
                      X509_ALGOR *alg);
 void X509_ALGOR_set_md(X509_ALGOR *alg, const EVP_MD *md);
 int X509_ALGOR_cmp(const X509_ALGOR *a, const X509_ALGOR *b);

=head1 DESCRIPTION

The functions d2i_X509() and i2d_X509() decode and encode an B<X509_ALGOR>
structure which is equivalent to the B<AlgorithmIdentifier> structure.

Otherwise they behave in a similar way to d2i_X509() and i2d_X509()
described in the L<d2i_X509(3)|d2i_X509(3)> manual page.

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

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

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

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

X509_ALGOR_cmp() compares B<a> and B<b> and returns 0 if they have identical
encodings and non-zero otherwise.

=head1 SEE ALSO

L<d2i_X509(3)|d2i_X509(3)>

=head1 HISTORY

TBA

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