=pod

=head1 NAME

OSSL_ENCODER_to_data,
OSSL_ENCODER_to_bio,
OSSL_ENCODER_to_fp
- Routines to perform an encoding

=head1 SYNOPSIS

 #include <openssl/encoder.h>

 int OSSL_ENCODER_to_data(OSSL_ENCODER_CTX *ctx, unsigned char **pdata,
                          size_t *pdata_len);
 int OSSL_ENCODER_to_bio(OSSL_ENCODER_CTX *ctx, BIO *out);
 int OSSL_ENCODER_to_fp(OSSL_ENCODER_CTX *ctx, FILE *fp);

Feature availability macros:

=over 4

=item OSSL_ENCODER_to_fp() is only available when B<OPENSSL_NO_STDIO>
is undefined.

=back

=head1 DESCRIPTION

OSSL_ENCODER_to_data() runs the encoding process for the context I<ctx>,
with the output going to the I<*pdata> and I<*pdata_len>.
If I<*pdata> is NULL when OSSL_ENCODER_to_data() is called, a buffer will be
allocated using L<OPENSSL_zalloc(3)>, and I<*pdata> will be set to point at
the start of that buffer, and I<*pdata_len> will be assigned its length when
OSSL_ENCODER_to_data() returns.
If I<*pdata> is non-NULL when OSSL_ENCODER_to_data() is called, I<*pdata_len>
is assumed to have its size.  In this case, I<*pdata> will be set to point
after the encoded bytes, and I<*pdata_len> will be assigned the number of
remaining bytes.

OSSL_ENCODER_to_bio() runs the encoding process for the context I<ctx>, with
the output going to the B<BIO> I<out>.

OSSL_ENCODER_to_fp() does the same thing as OSSL_ENCODER_to_bio(), except
that the output is going to the B<FILE> I<fp>.

=for comment Know your encoder!

For OSSL_ENCODER_to_bio() and OSSL_ENCODER_to_fp(), the application is
required to set up the B<BIO> or B<FILE> properly, for example to have
it in text or binary mode as is appropriate for the encoder output type.

=head1 RETURN VALUES

OSSL_ENCODER_to_bio(), OSSL_ENCODER_to_fp() and OSSL_ENCODER_to_data()
return 1 on success, or 0 on failure.

=head1 EXAMPLES

To encode a pkey as PKCS#8 with PEM format into a bio:

 OSSL_ENCODER_CTX *ectx;
 const char *format = "PEM";
 const char *structure = "PrivateKeyInfo"; /* PKCS#8 structure */
 const unsigned char *pass = "my password";

 ectx = OSSL_ENCODER_CTX_new_for_pkey(pkey,
                                      OSSL_KEYMGMT_SELECT_KEYPAIR
                                      | OSSL_KEYMGMT_SELECT_DOMAIN_PARAMETERS,
                                      format, structure,
                                      NULL);
 if (ectx == NULL) {
     /* error: no suitable potential encoders found */
 }
 if (pass != NULL)
     OSSL_ENCODER_CTX_set_passphrase(ectx, pass, strlen(pass));
 if (OSSL_ENCODER_to_bio(ectx, bio)) {
     /* pkey was successfully encoded into the bio */
 } else {
     /* encoding failure */
 }
 OSSL_ENCODER_CTX_free(ectx);

To encode a pkey as PKCS#8 with DER format encrypted with
AES-256-CBC into a buffer:

 OSSL_ENCODER_CTX *ectx;
 const char *format = "DER";
 const char *structure = "PrivateKeyInfo"; /* PKCS#8 structure */
 const unsigned char *pass = "my password";
 unsigned char *data = NULL;
 size_t datalen;

 ectx = OSSL_ENCODER_CTX_new_for_pkey(pkey,
                                      OSSL_KEYMGMT_SELECT_KEYPAIR
                                      | OSSL_KEYMGMT_SELECT_DOMAIN_PARAMETERS,
                                      format, structure,
                                      NULL);
 if (ectx == NULL) {
     /* error: no suitable potential encoders found */
 }
 if (pass != NULL) {
     OSSL_ENCODER_CTX_set_passphrase(ectx, pass, strlen(pass));
     OSSL_ENCODER_CTX_set_cipher(ctx, "AES-256-CBC", NULL);
 }
 if (OSSL_ENCODER_to_data(ectx, &data, &datalen)) {
     /*
      * pkey was successfully encoded into a newly allocated
      * data buffer
      */
 } else {
     /* encoding failure */
 }
 OSSL_ENCODER_CTX_free(ectx);

=head1 SEE ALSO

L<provider(7)>, L<OSSL_ENCODER_CTX(3)>

=head1 HISTORY

The functions described here were added in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2019-2021 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