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=pod

=head1 NAME

CRYPTO_set_ex_data, CRYPTO_get_ex_data - internal application specific data functions

=head1 SYNOPSIS

 #include <openssl/crypto.h>

 int CRYPTO_set_ex_data(CRYPTO_EX_DATA *r, int idx, void *arg);

 void *CRYPTO_get_ex_data(CRYPTO_EX_DATA *r, int idx);

=head1 DESCRIPTION

Several OpenSSL structures can have application specific data attached to them.
These functions are used internally by OpenSSL to manipulate application
specific data attached to a specific structure.

These functions should only be used by applications to manipulate
B<CRYPTO_EX_DATA> structures passed to the B<new_func()>, B<free_func()> and
B<dup_func()> callbacks: as passed to B<RSA_get_ex_new_index()> for example.

B<CRYPTO_set_ex_data()> is used to set application specific data, the data is
supplied in the B<arg> parameter and its precise meaning is up to the
application.

B<CRYPTO_get_ex_data()> is used to retrieve application specific data. The data
is returned to the application, this will be the same value as supplied to
a previous B<CRYPTO_set_ex_data()> call.

=head1 RETURN VALUES

B<CRYPTO_set_ex_data()> returns 1 on success or 0 on failure.

B<CRYPTO_get_ex_data()> returns the application data or 0 on failure. 0 may also
be valid application data but currently it can only fail if given an invalid B<idx>
parameter.

On failure an error code can be obtained from L<ERR_get_error(3)|ERR_get_error(3)>.

=head1 SEE ALSO

L<RSA_get_ex_new_index(3)|RSA_get_ex_new_index(3)>,
L<DSA_get_ex_new_index(3)|DSA_get_ex_new_index(3)>,
L<DH_get_ex_new_index(3)|DH_get_ex_new_index(3)>

=head1 HISTORY

CRYPTO_set_ex_data() and CRYPTO_get_ex_data() have been available since SSLeay 0.9.0.

=cut