=pod

=head1 NAME

RAND_DRBG_set_ex_data,
RAND_DRBG_get_ex_data,
RAND_DRBG_get_ex_new_index
- store and retrieve extra data from the DRBG instance

=head1 SYNOPSIS

 #include <openssl/rand_drbg.h>

 int RAND_DRBG_set_ex_data(RAND_DRBG *drbg, int idx, void *data);

 void *RAND_DRBG_get_ex_data(const RAND_DRBG *drbg, int idx);

 int RAND_DRBG_get_ex_new_index(long argl, void *argp,
                                CRYPTO_EX_new *new_func,
                                CRYPTO_EX_dup *dup_func,
                                CRYPTO_EX_free *free_func);



=head1 DESCRIPTION

RAND_DRBG_set_ex_data() enables an application to store arbitrary application
specific data B<data> in a RAND_DRBG instance B<drbg>. The index B<idx> should
be a value previously returned from a call to RAND_DRBG_get_ex_new_index().

RAND_DRBG_get_ex_data() retrieves application specific data previously stored
in an RAND_DRBG instance B<drbg>. The B<idx> value should be the same as that
used when originally storing the data.

For more detailed information see L<CRYPTO_get_ex_data(3)> and
L<CRYPTO_set_ex_data(3)> which implement these functions and
L<CRYPTO_get_ex_new_index(3)> for generating a unique index.

=head1 RETURN VALUES

RAND_DRBG_set_ex_data() returns 1 for success or 0 for failure.

RAND_DRBG_get_ex_data() returns the previously stored value or NULL on
failure. NULL may also be a valid value.


=head1 NOTES

RAND_DRBG_get_ex_new_index(...) is implemented as a macro and equivalent to
CRYPTO_get_ex_new_index(CRYPTO_EX_INDEX_DRBG,...).

=head1 SEE ALSO

L<CRYPTO_get_ex_data(3)>,
L<CRYPTO_set_ex_data(3)>,
L<CRYPTO_get_ex_new_index(3)>,
L<RAND_DRBG(7)>

=head1 COPYRIGHT

Copyright 2017-2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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