@deftypefun {int} {gnutls_pubkey_export} (gnutls_pubkey_t @var{key}, gnutls_x509_crt_fmt_t @var{format}, void * @var{output_data}, size_t * @var{output_data_size})
@var{key}: Holds the certificate

@var{format}: the format of output params. One of PEM or DER.

@var{output_data}: will contain a certificate PEM or DER encoded

@var{output_data_size}: holds the size of output_data (and will be
replaced by the actual size of parameters)

This function will export the public key to DER or PEM format.
The contents of the exported data is the SubjectPublicKeyInfo
X.509 structure.

If the buffer provided is not long enough to hold the output, then
*output_data_size is updated and @code{GNUTLS_E_SHORT_MEMORY_BUFFER}  will
be returned.

If the structure is PEM encoded, it will have a header
of "BEGIN CERTIFICATE".

@strong{Returns:} In case of failure a negative error code will be
returned, and 0 on success.

@strong{Since:} 2.12.0
@end deftypefun