=pod

=head1 NAME

EVP_ASYM_CIPHER_fetch, EVP_ASYM_CIPHER_free, EVP_ASYM_CIPHER_up_ref,
EVP_ASYM_CIPHER_number, EVP_ASYM_CIPHER_is_a, EVP_ASYM_CIPHER_provider,
EVP_ASYM_CIPHER_do_all_provided, EVP_ASYM_CIPHER_names_do_all
- Functions to manage EVP_ASYM_CIPHER algorithm objects

=head1 SYNOPSIS

 #include <openssl/evp.h>

 EVP_ASYM_CIPHER *EVP_ASYM_CIPHER_fetch(OPENSSL_CTX *ctx, const char *algorithm,
                                        const char *properties);
 void EVP_ASYM_CIPHER_free(EVP_ASYM_CIPHER *cipher);
 int EVP_ASYM_CIPHER_up_ref(EVP_ASYM_CIPHER *cipher);
 int EVP_ASYM_CIPHER_number(const EVP_ASYM_CIPHER *cipher);
 int EVP_ASYM_CIPHER_is_a(const EVP_ASYM_CIPHER *cipher, const char *name);
 OSSL_PROVIDER *EVP_ASYM_CIPHER_provider(const EVP_ASYM_CIPHER *cipher);
 void EVP_ASYM_CIPHER_do_all_provided(OPENSSL_CTX *libctx,
                                      void (*fn)(EVP_ASYM_CIPHER *cipher,
                                                 void *arg),
                                      void *arg);
 void EVP_ASYM_CIPHER_names_do_all(const EVP_ASYM_CIPHER *cipher,
                                   void (*fn)(const char *name, void *data),
                                   void *data);

=head1 DESCRIPTION

EVP_ASYM_CIPHER_fetch() fetches the implementation for the given
B<algorithm> from any provider offering it, within the criteria given
by the B<properties> and in the scope of the given library context B<ctx> (see
L<OPENSSL_CTX(3)>). The algorithm will be one offering functions for performing
asymmetric cipher related tasks such as asymmetric encryption and decryption.
See L<provider(7)/Fetching algorithms> for further information.

The returned value must eventually be freed with EVP_ASYM_CIPHER_free().

EVP_ASYM_CIPHER_free() decrements the reference count for the B<EVP_ASYM_CIPHER>
structure. Typically this structure will have been obtained from an earlier call
to EVP_ASYM_CIPHER_fetch(). If the reference count drops to 0 then the
structure is freed.

EVP_ASYM_CIPHER_up_ref() increments the reference count for an
B<EVP_ASYM_CIPHER> structure.

EVP_ASYM_CIPHER_is_a() returns 1 if I<cipher> is an implementation of an
algorithm that's identifiable with I<name>, otherwise 0.

EVP_ASYM_CIPHER_provider() returns the provider that I<cipher> was fetched from.

EVP_ASYM_CIPHER_do_all_provided() traverses all EVP_ASYM_CIPHERs implemented by
all activated providers in the given library context I<libctx>, and for each of
the implementations, calls the given function I<fn> with the implementation
method and the given I<arg> as argument.

EVP_ASYM_CIPHER_number() returns the internal dynamic number assigned to
I<cipher>.

EVP_ASYM_CIPHER_names_do_all() traverses all names for I<cipher>, and calls
I<fn> with each name and I<data>.

=head1 RETURN VALUES

EVP_ASYM_CIPHER_fetch() returns a pointer to an B<EVP_ASYM_CIPHER> for success
or B<NULL> for failure.

EVP_ASYM_CIPHER_up_ref() returns 1 for success or 0 otherwise.

=head1 SEE ALSO

L<provider(7)/Fetching algorithms>, L<OSSL_PROVIDER(3)>

=head1 HISTORY

The functions described here were added in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2019 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