NAME

       SSL_pending, SSL_has_pending - check for readable bytes buffered in an SSL object

SYNOPSIS

        #include <openssl/ssl.h>

        int SSL_pending(const SSL *ssl);
        int SSL_has_pending(const SSL *s);

DESCRIPTION

       Data is received in whole blocks known as records from the peer. A whole record is
       processed (e.g. decrypted) in one go and is buffered by OpenSSL until it is read by the
       application via a call to SSL_read_ex(3) or SSL_read(3).

       SSL_pending() returns the number of bytes which have been processed, buffered and are
       available inside ssl for immediate read.

       If the SSL object's read_ahead flag is set (see SSL_CTX_set_read_ahead(3)), additional
       protocol bytes (beyond the current record) may have been read containing more TLS/SSL
       records. This also applies to DTLS and pipelining (see
       SSL_CTX_set_split_send_fragment(3)). These additional bytes will be buffered by OpenSSL
       but will remain unprocessed until they are needed. As these bytes are still in an
       unprocessed state SSL_pending() will ignore them. Therefore it is possible for no more
       bytes to be readable from the underlying BIO (because OpenSSL has already read them) and
       for SSL_pending() to return 0, even though readable application data bytes are available
       (because the data is in unprocessed buffered records).

       SSL_has_pending() returns 1 if s has buffered data (whether processed or unprocessed) and
       0 otherwise. Note that it is possible for SSL_has_pending() to return 1, and then a
       subsequent call to SSL_read_ex() or SSL_read() to return no data because the unprocessed
       buffered data when processed yielded no application data (for example this can happen
       during renegotiation). It is also possible in this scenario for SSL_has_pending() to
       continue to return 1 even after an SSL_read_ex() or SSL_read() call because the buffered
       and unprocessed data is not yet processable (e.g. because OpenSSL has only received a
       partial record so far).

RETURN VALUES

       SSL_pending() returns the number of buffered and processed application data bytes that are
       pending and are available for immediate read. SSL_has_pending() returns 1 if there is
       buffered record data in the SSL object and 0 otherwise.

SEE ALSO

       SSL_read_ex(3), SSL_read(3), SSL_CTX_set_read_ahead(3),
       SSL_CTX_set_split_send_fragment(3), ssl(7)

HISTORY

       The SSL_has_pending() function was added in OpenSSL 1.1.0.

COPYRIGHT

       Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use this file except in
       compliance with the License.  You can obtain a copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.