BIO_ctrl man page on DigitalUNIX

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BIO_ctrl(3)							   BIO_ctrl(3)

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

SYNOPSIS
       #include <openssl/bio.h>

       long BIO_ctrl(
	       BIO *bp,
	       int cmd,
	       long larg,
	       void *parg ); long BIO_callback_ctrl(
	       BIO *b,
	       int cmd,
	       void (*fp)(struct bio_st *,
	       int,
	       const char *,
	       int,
	       long,
	       long) ); 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 ); typedef void bio_info_cb(
	       BIO *b,
	       int oper,
	       const char *ptr,
	       int arg1,
	       long arg2,
	       long arg3 );

DESCRIPTION
       The BIO_ctrl(), BIO_callback_ctrl(), BIO_ptr_ctrl(), and BIO_int_ctrl()
       functions are BIO control operations taking arguments of various types.
       These functions are not usually 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 BIO's	refer‐
       ence page, as well as any special features of the standard calls.

       The  BIO_reset()function	 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.

       The  BIO_seek() function resets a file related BIO's (its file descrip‐
       tor and FILE BIOs) file position pointer to ofs	bytes  from  start  of
       file.

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

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

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

       The  BIO_set_close()  function 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.

       The BIO_get_close() function returns the BIO's close flag.

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

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

       The return values of the	 BIO_pending()	and  BIO_wpending()  functions
       might  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 structure's internal buffers but it is not possible to deter‐
       mine this in a portably way. For other types of BIO they might  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 par‐
       ticular operation. It can be called on a chain and it will be automati‐
       cally  passed  to  the relevant BIO. However, this can cause unexpected
       results. For example, no current filter BIOs implement BIO_seek(),  but
       this might still succeed if the chain ends in a FILE or file descriptor
       BIO.

       Source/sink BIOs return a 0 if they do  not  recognize  the  BIO_ctrl()
       operation.

RESTRICTIONS
       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.

RETURN VALUES
       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 fail‐
       ure.

       BIO_seek() and BIO_tell() both return the current file position on suc‐
       cess  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.

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

SEE ALSO
       TBA

								   BIO_ctrl(3)
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