BIO_ctrl_get_read_request - Find out how much bytes are were requested from the BIO
size_t BIO_ctrl_get_read_request(BIO *bio);
BIO_ctrl_get_read_request() returns the number of bytes that
were last requested from bio by a
BIO_read() operation. This is useful e.g. for BIO pairs,
so that the application knows how much bytes to supply to bio.
When bio is NULL, the OpenSSL library calls
The following return values can occur:
The number of bytes requested.