Verifies the signature. If istream is a clearsigned stream, you
should pass null as the sigstream parameter and may wish to
provide an ostream argument for GMime to output the original
plaintext into. Otherwise sigstream is assumed to be the signature
stream and is used to verify the integirity of the istream.
Verifies the signature. If istream is a clearsigned stream, you should pass null as the sigstream parameter and may wish to provide an ostream argument for GMime to output the original plaintext into. Otherwise sigstream is assumed to be the signature stream and is used to verify the integirity of the istream.