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>.

3.0.13                                             2025-09-18                                  SSL_PENDING(3SSL)