Refer to SSL_pending from the man page for SSL_read (787287af) · Commits · CYBER - Cyber Security / TS 103 523 MSP / TLMSP / TLMSP OpenSSL

doc/ssl/SSL_read.pod

+6 −0

Original line number	Diff line number	Diff line
		@@ -64,6 +64,11 @@ non-blocking socket, nothing is to be done, but select() can be used to check
		for the required condition. When using a buffering BIO, like a BIO pair, data
		must be written into or retrieved out of the BIO before being able to continue.

		L<SSL_pending(3)\|SSL_pending(3)> can be used to find out whether there
		are buffered bytes available for immediate retrieval. In this case
		SSL_read() can be called without blocking or actually receiving new
		data from the underlying socket.

		=head1 WARNING

		When an SSL_read() operation has to be repeated because of
		@@ -112,6 +117,7 @@ L<SSL_get_error(3)\|SSL_get_error(3)>, L<SSL_write(3)\|SSL_write(3)>,
		L<SSL_CTX_set_mode(3)\|SSL_CTX_set_mode(3)>, L<SSL_CTX_new(3)\|SSL_CTX_new(3)>,
		L<SSL_connect(3)\|SSL_connect(3)>, L<SSL_accept(3)\|SSL_accept(3)>
		L<SSL_set_connect_state(3)\|SSL_set_connect_state(3)>,
		L<SSL_pending(3)\|SSL_pending(3)>,
		L<SSL_shutdown(3)\|SSL_shutdown(3)>, L<SSL_set_shutdown(3)\|SSL_set_shutdown(3)>,
		L<ssl(3)\|ssl(3)>, L<bio(3)\|bio(3)>