|BIO_CTRL(3)||Library Functions Manual||BIO_CTRL(3)|
bio_info_cb — BIO control
int cmd, long larg,
int cmd, bio_info_cb cb);
int cmd, long larg);
int cmd, long larg,
int oper, const char *ptr,
int arg1, long arg2,
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 BIO's 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
BIO_set_close() sets the BIO
b close flag to flag.
flag can take the value
BIO_CLOSE is used in a source/sink BIO to
indicate that the underlying I/O stream should be closed when the BIO is
BIO_get_close() returns the BIO's close
BIO_ctrl_wpending() return the number of pending
characters in the BIO's read and write buffers. Not all BIOs support these
BIO_ctrl_wpending() return a
size_t type and are functions.
BIO_wpending() are macros which call
BIO_reset() normally returns 1 for success
and 0 or -1 for failure. File BIOs are an exception, returning 0 for success
and -1 for failure.
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
BIO_flush() returns 1 for success and 0 or
-1 for failure.
BIO_eof() returns 1 if EOF has been
reached or 0 otherwise.
BIO_set_close() always returns 1.
BIO_get_close() returns the close flag
BIO_ctrl_wpending() return the amount of pending
Because it can write data,
return 0 or -1 indicating that the call should be retried later in a similar
manner to BIO_write(3). The
BIO_should_retry(3) call should
be used and appropriate action taken if the call fails.
The return values of
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 structure's internal
buffers but it is not possible to determine this in a portable way. For
other types of BIO they may not be supported.
If they do not internally handle a particular
BIO_ctrl() operation, filter BIOs 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_pending() first appeared in SSLeay 0.6.0.
BIO_wpending() first appeared in SSLeay 0.8.1.
BIO_set_info_callback() first appeared in SSLeay
0.9.0. All these functions have been available since
BIO_tell() first appeared in SSLeay 0.9.1.
BIO_ctrl_wpending() first appeared in OpenSSL 0.9.4.
These functions have been available since OpenBSD
BIO_callback_ctrl() first appeared in
OpenSSL 0.9.5 and has been available since OpenBSD
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
BIO_seek() on a file BIO for a successful
|March 27, 2018||OpenBSD-current|