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 2000-2020 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (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>.