BIO_ctrl(3)

     BIO_ctrl(3)            0.9.6h (2000-09-18)            BIO_ctrl(3)

     NAME
          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 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
          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.

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     BIO_ctrl(3)            0.9.6h (2000-09-18)            BIO_ctrl(3)

          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_ctrl().

     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 failure.

          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.

     NOTES
          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().  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

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     BIO_ctrl(3)            0.9.6h (2000-09-18)            BIO_ctrl(3)

          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() operation.

     BUGS
          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.

     SEE ALSO
          TBA

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