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       SSL_waiting_for_async, SSL_get_all_async_fds, SSL_get_changed_async_fds - manage
       asynchronous operations


        #include <openssl/async.h>
        #include <openssl/ssl.h>

        int SSL_waiting_for_async(SSL *s);
        int SSL_get_all_async_fds(SSL *s, OSSL_ASYNC_FD *fd, size_t *numfds);
        int SSL_get_changed_async_fds(SSL *s, OSSL_ASYNC_FD *addfd, size_t *numaddfds,
                                      OSSL_ASYNC_FD *delfd, size_t *numdelfds);


       SSL_waiting_for_async() determines whether an SSL connection is currently waiting for
       asynchronous operations to complete (see the SSL_MODE_ASYNC mode in SSL_CTX_set_mode(3)).

       SSL_get_all_async_fds() returns a list of file descriptor which can be used in a call to
       select() or poll() to determine whether the current asynchronous operation has completed
       or not. A completed operation will result in data appearing as "read ready" on the file
       descriptor (no actual data should be read from the file descriptor). This function should
       only be called if the SSL object is currently waiting for asynchronous work to complete
       (i.e.  SSL_ERROR_WANT_ASYNC has been received - see SSL_get_error(3)). Typically the list
       will only contain one file descriptor. However if multiple asynchronous capable engines
       are in use then more than one is possible. The number of file descriptors returned is
       stored in *numfds and the file descriptors themselves are in *fds. The fds parameter may
       be NULL in which case no file descriptors are returned but *numfds is still populated. It
       is the callers responsibility to ensure sufficient memory is allocated at *fds so
       typically this function is called twice (once with a NULL fds parameter and once without).

       SSL_get_changed_async_fds() returns a list of the asynchronous file descriptors that have
       been added and a list that have been deleted since the last SSL_ERROR_WANT_ASYNC was
       received (or since the SSL object was created if no SSL_ERROR_WANT_ASYNC has been
       received). Similar to SSL_get_all_async_fds() it is the callers responsibility to ensure
       that *addfd and *delfd have sufficient memory allocated, although they may be NULL. The
       number of added fds and the number of deleted fds are stored in *numaddfds and *numdelfds


       SSL_waiting_for_async() will return 1 if the current SSL operation is waiting for an async
       operation to complete and 0 otherwise.

       SSL_get_all_async_fds() and SSL_get_changed_async_fds() return 1 on success or 0 on error.


       On Windows platforms the openssl/async.h header is dependent on some of the types
       customarily made available by including windows.h. The application developer is likely to
       require control over when the latter is included, commonly as one of the first included
       headers. Therefore it is defined as an application developer's responsibility to include
       windows.h prior to async.h.


       SSL_get_error(3), SSL_CTX_set_mode(3)


       The SSL_waiting_for_async(), SSL_get_all_async_fds() and SSL_get_changed_async_fds()
       functions were added in OpenSSL 1.1.0.


       Copyright 2016 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 <>.