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BIO_CTRL(3)			    OpenSSL			   BIO_CTRL(3)

       BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl,	BIO_reset,
       BIO_seek, BIO_tell, BIO_flush, BIO_eof, BIO_set_close, BIO_get_close,
       BIO_pending, BIO_wpending, BIO_ctrl_pending, BIO_ctrl_wpending,
       BIO_get_info_callback, BIO_set_info_callback, BIO_info_cb - BIO control

	#include <openssl/bio.h>

	typedef	int BIO_info_cb(BIO *b,	int state, int res);

	long BIO_ctrl(BIO *bp, int cmd,	long larg, void	*parg);
	long BIO_callback_ctrl(BIO *b, int cmd,	BIO_info_cb *cb);
	char *BIO_ptr_ctrl(BIO *bp, int	cmd, long larg);
	long BIO_int_ctrl(BIO *bp, int cmd, long larg, int iarg);

	int BIO_reset(BIO *b);
	int BIO_seek(BIO *b, int ofs);
	int BIO_tell(BIO *b);
	int BIO_flush(BIO *b);
	int BIO_eof(BIO	*b);
	int BIO_set_close(BIO *b, long flag);
	int BIO_get_close(BIO *b);
	int BIO_pending(BIO *b);
	int BIO_wpending(BIO *b);
	size_t BIO_ctrl_pending(BIO *b);
	size_t BIO_ctrl_wpending(BIO *b);

	int BIO_get_info_callback(BIO *b, BIO_info_cb **cbp);
	int BIO_set_info_callback(BIO *b, BIO_info_cb *cb);

       BIO_ctrl(), BIO_callback_ctrl(),	BIO_ptr_ctrl() and BIO_int_ctrl() are
       BIO "control" operations	taking arguments of various types.  These
       functions are not normally called directly, various macros are used
       instead.	The standard macros are	described below, macros	specific to a
       particular type of BIO are described in the specific BIOs manual	page
       as well as any special features of the standard calls.

       BIO_reset() typically resets a BIO to some initial state, in the	case
       of file related BIOs for	example	it rewinds the file pointer to the
       start of	the file.

       BIO_seek() resets a file	related	BIO's (that is file descriptor and
       FILE BIOs) file position	pointer	to ofs bytes from start	of file.

       BIO_tell() returns the current file position of a file related BIO.

       BIO_flush() normally writes out any internally buffered data, in	some
       cases it	is used	to signal EOF and that no more data will be written.

       BIO_eof() returns 1 if the BIO has read EOF, the	precise	meaning	of
       "EOF" varies according to the BIO type.

       BIO_set_close() sets the	BIO b close flag to flag. flag can take	the
       value BIO_CLOSE or BIO_NOCLOSE. Typically BIO_CLOSE is used in a
       source/sink BIO to indicate that	the underlying I/O stream should be
       closed when the BIO is freed.

       BIO_get_close() returns the BIOs	close flag.

       BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and
       BIO_ctrl_wpending() return the number of	pending	characters in the BIOs
       read and	write buffers.	Not all	BIOs support these calls.
       BIO_ctrl_pending() and BIO_ctrl_wpending() return a size_t type and are
       functions, BIO_pending()	and BIO_wpending() are macros which call

       BIO_reset() normally returns 1 for success and 0	or -1 for failure.
       File BIOs are an	exception, they	return 0 for success and -1 for

       BIO_seek() and BIO_tell() both return the current file position on
       success and -1 for failure, except file BIOs which for BIO_seek()
       always return 0 for success and -1 for failure.

       BIO_flush() returns 1 for success and 0 or -1 for failure.

       BIO_eof() returns 1 if EOF has been reached 0 otherwise.

       BIO_set_close() always returns 1.

       BIO_get_close() returns the close flag value: BIO_CLOSE or BIO_NOCLOSE.

       BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and
       BIO_ctrl_wpending() return the amount of	pending	data.

       BIO_flush(), because it can write data may return 0 or -1 indicating
       that the	call should be retried later in	a similar manner to
       BIO_write_ex().	The BIO_should_retry() call should be used and
       appropriate action taken	is the call fails.

       The return values of BIO_pending() and BIO_wpending() may not reliably
       determine the amount of pending data in all cases. For example in the
       case of a file BIO some data may	be available in	the FILE structures
       internal	buffers	but it is not possible to determine this in a portably
       way. For	other types of BIO they	may not	be supported.

       Filter BIOs if they do not internally handle a particular BIO_ctrl()
       operation usually pass the operation to the next	BIO in the chain.
       This often means	there is no need to locate the required	BIO for	a
       particular operation, it	can be called on a chain and it	will be
       automatically passed to the relevant BIO. However, this can cause
       unexpected results: for example no current filter BIOs implement
       BIO_seek(), but this may	still succeed if the chain ends	in a FILE or
       file descriptor BIO.

       Source/sink BIOs	return an 0 if they do not recognize the BIO_ctrl()

       Some of the return values are ambiguous and care	should be taken. In
       particular a return value of 0 can be returned if an operation is not
       supported, if an	error occurred,	if EOF has not been reached and	in the
       case of BIO_seek() on a file BIO	for a successful operation.

       Copyright 2000-2020 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

1.1.1h				  2020-09-22			   BIO_CTRL(3)


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