=pod

=head1 NAME

OSSL_ENCODER,
OSSL_ENCODER_fetch,
OSSL_ENCODER_up_ref,
OSSL_ENCODER_free,
OSSL_ENCODER_provider,
OSSL_ENCODER_properties,
OSSL_ENCODER_is_a,
OSSL_ENCODER_number,
OSSL_ENCODER_do_all_provided,
OSSL_ENCODER_names_do_all,
OSSL_ENCODER_gettable_params,
OSSL_ENCODER_get_params
- Encoder method routines

=head1 SYNOPSIS

 #include <openssl/encoder.h>

 typedef struct ossl_encoder_st OSSL_ENCODER;

 OSSL_ENCODER *OSSL_ENCODER_fetch(OPENSSL_CTX *ctx, const char *name,
                                  const char *properties);
 int OSSL_ENCODER_up_ref(OSSL_ENCODER *encoder);
 void OSSL_ENCODER_free(OSSL_ENCODER *encoder);
 const OSSL_PROVIDER *OSSL_ENCODER_provider(const OSSL_ENCODER *encoder);
 const char *OSSL_ENCODER_properties(const OSSL_ENCODER *encoder);
 int OSSL_ENCODER_is_a(const OSSL_ENCODER *encoder, const char *name);
 int OSSL_ENCODER_number(const OSSL_ENCODER *encoder);
 void OSSL_ENCODER_do_all_provided(OPENSSL_CTX *libctx,
                                   void (*fn)(OSSL_ENCODER *encoder, void *arg),
                                   void *arg);
 void OSSL_ENCODER_names_do_all(const OSSL_ENCODER *encoder,
                                void (*fn)(const char *name, void *data),
                                void *data);
 const OSSL_PARAM *OSSL_ENCODER_gettable_params(OSSL_ENCODER *encoder);
 int OSSL_ENCODER_get_params(OSSL_ENCODER_CTX *ctx, const OSSL_PARAM params[]);

=head1 DESCRIPTION

B<OSSL_ENCODER> is a method for encoders, which know how to
encode an object of some kind to a encoded form, such as PEM,
DER, or even human readable text.

OSSL_ENCODER_fetch() looks for an algorithm within the provider that
has been loaded into the B<OPENSSL_CTX> given by I<ctx>, having the
name given by I<name> and the properties given by I<properties>.
The I<name> determines what type of object the fetched encoder
method is expected to be able to encode, and the properties are
used to determine the expected output type.
For known properties and the values they may have, please have a look
in L<provider-encoder(7)/Names and properties>.

OSSL_ENCODER_up_ref() increments the reference count for the given
I<encoder>.

OSSL_ENCODER_free() decrements the reference count for the given
I<encoder>, and when the count reaches zero, frees it.

OSSL_ENCODER_provider() returns the provider of the given
I<encoder>.

OSSL_ENCODER_provider() returns the property definition associated
with the given I<encoder>.

OSSL_ENCODER_is_a() checks if I<encoder> is an implementation of an
algorithm that's identifiable with I<name>.

OSSL_ENCODER_number() returns the internal dynamic number assigned to
the given I<encoder>.

OSSL_ENCODER_names_do_all() traverses all names for the given
I<encoder>, and calls I<fn> with each name and I<data>.

OSSL_ENCODER_do_all_provided() traverses all encoder
implementations by all activated providers in the library context
I<libctx>, and for each of the implementations, calls I<fn> with the
implementation method and I<data> as arguments.

OSSL_ENCODER_gettable_params() returns an L<OSSL_PARAM(3)>
array of parameter descriptors.

OSSL_ENCODER_get_params() attempts to get parameters specified
with an L<OSSL_PARAM(3)> array I<params>.  Parameters that the
implementation doesn't recognise should be ignored.

=head1 NOTES

OSSL_ENCODER_fetch() may be called implicitly by other fetching
functions, using the same library context and properties.
Any other API that uses keys will typically do this.

=head1 RETURN VALUES

OSSL_ENCODER_fetch() returns a pointer to the key management
implementation represented by an OSSL_ENCODER object, or NULL on
error.

OSSL_ENCODER_up_ref() returns 1 on success, or 0 on error.

OSSL_ENCODER_free() doesn't return any value.

OSSL_ENCODER_provider() returns a pointer to a provider object, or
NULL on error.

OSSL_ENCODER_properties() returns a pointer to a property
definition string, or NULL on error.

OSSL_ENCODER_is_a() returns 1 of I<encoder> was identifiable,
otherwise 0.

OSSL_ENCODER_number() returns an integer.

=head1 SEE ALSO

L<provider(7)>, L<OSSL_ENCODER_CTX(3)>, L<OSSL_ENCODER_to_bio(3)>,
L<OSSL_ENCODER_CTX_new_by_EVP_PKEY(3)>, L<OPENSSL_CTX(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