BIO_ctrl(3)                 OpenSSL                 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_call-
       back, 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 argu-
       ments of various types.  These functions are not nor-
       mally 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 spe-
       cific 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 charac-
       ters 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 func-
       tions, 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 fail-
       ure.

       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 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 particu-
       lar 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 opera-
       tion, it can be called on a chain and it will be auto-
       matically 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



0.9.7c                     2000-09-19               BIO_ctrl(3)
