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-=pod
-
-=head1 NAME
-
-SSL_read - read bytes from a TLS/SSL connection.
-
-=head1 SYNOPSIS
-
- #include <openssl/ssl.h>
-
- int SSL_read(SSL *ssl, void *buf, int num);
-
-=head1 DESCRIPTION
-
-SSL_read() tries to read B<num> bytes from the specified B<ssl> into the
-buffer B<buf>.
-
-=head1 NOTES
-
-If necessary, SSL_read() will negotiate a TLS/SSL session, if
-not already explicitly performed by L<SSL_connect(3)|SSL_connect(3)> or
-L<SSL_accept(3)|SSL_accept(3)>. If the
-peer requests a re-negotiation, it will be performed transparently during
-the SSL_read() operation. The behaviour of SSL_read() depends on the
-underlying BIO.
-
-For the transparent negotiation to succeed, the B<ssl> must have been
-initialized to client or server mode. This is being done by calling
-L<SSL_set_connect_state(3)|SSL_set_connect_state(3)> or SSL_set_accept_state()
-before the first call to an SSL_read() or L<SSL_write(3)|SSL_write(3)>
-function.
-
-SSL_read() works based on the SSL/TLS records. The data are received in
-records (with a maximum record size of 16kB for SSLv3/TLSv1). Only when a
-record has been completely received, it can be processed (decryption and
-check of integrity). Therefore data that was not retrieved at the last
-call of SSL_read() can still be buffered inside the SSL layer and will be
-retrieved on the next call to SSL_read(). If B<num> is higher than the
-number of bytes buffered, SSL_read() will return with the bytes buffered.
-If no more bytes are in the buffer, SSL_read() will trigger the processing
-of the next record. Only when the record has been received and processed
-completely, SSL_read() will return reporting success. At most the contents
-of the record will be returned. As the size of an SSL/TLS record may exceed
-the maximum packet size of the underlying transport (e.g. TCP), it may
-be necessary to read several packets from the transport layer before the
-record is complete and SSL_read() can succeed.
-
-If the underlying BIO is B<blocking>, SSL_read() will only return, once the
-read operation has been finished or an error occurred, except when a
-renegotiation take place, in which case a SSL_ERROR_WANT_READ may occur.
-This behaviour can be controlled with the SSL_MODE_AUTO_RETRY flag of the
-L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)> call.
-
-If the underlying BIO is B<non-blocking>, SSL_read() will also return
-when the underlying BIO could not satisfy the needs of SSL_read()
-to continue the operation. In this case a call to
-L<SSL_get_error(3)|SSL_get_error(3)> with the
-return value of SSL_read() will yield B<SSL_ERROR_WANT_READ> or
-B<SSL_ERROR_WANT_WRITE>. As at any time a re-negotiation is possible, a
-call to SSL_read() can also cause write operations! The calling process
-then must repeat the call after taking appropriate action to satisfy the
-needs of SSL_read(). The action depends on the underlying BIO. When using a
-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
-B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE>, it must be repeated
-with the same arguments.
-
-=head1 RETURN VALUES
-
-The following return values can occur:
-
-=over 4
-
-=item E<gt> 0
-
-The read operation was successful.
-The return value is the number of bytes actually read from the TLS/SSL
-connection.
-
-=item Z<><= 0
-
-
-=item E<lt>0
-
-The read operation was not successful, because either the connection was closed,
-an error occurred or action must be taken by the calling process.
-Call L<SSL_get_error(3)> with the return value B<ret> to find out the reason.
-
-SSLv2 (deprecated) does not support a shutdown alert protocol, so it can
-only be detected, whether the underlying connection was closed. It cannot
-be checked, whether the closure was initiated by the peer or by something
-else.
-
-Old documentation indicated a difference between 0 and -1, and that -1 was
-retryable.
-You should instead call SSL_get_error() to find out if it's retryable.
-
-=back
-
-=head1 SEE ALSO
-
-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)>
-
-=cut