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_info_cb
—
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, 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);
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 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 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 BIO's close flag.
BIO_pending
(),
BIO_ctrl_pending
(),
BIO_wpending
(), and
BIO_ctrl_wpending
()
return the number of pending characters in the BIO's 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, returning 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 or 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
Because it can write data,
BIO_flush
()
may 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_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 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_ctrl
()
operation.
SEE ALSO
HISTORY
BIO_ctrl
(),
BIO_reset
(), BIO_flush
(),
BIO_eof
(), BIO_set_close
(),
BIO_get_close
(),
BIO_pending
(), and
BIO_wpending
() appeared in SSLeay 0.8.1b or earlier.
BIO_ptr_ctrl
(),
BIO_int_ctrl
(),
BIO_get_info_callback
() and
BIO_set_info_callback
() first appeared in SSLeay
0.9.0. All these functions have been available since
OpenBSD 2.4.
BIO_seek
() and
BIO_tell
() first appeared in SSLeay 0.9.1.
BIO_ctrl_pending
() and
BIO_ctrl_wpending
() first appeared in OpenSSL 0.9.4.
These functions have been available since OpenBSD
2.6.
BIO_callback_ctrl
() first appeared in
OpenSSL 0.9.5 and has been available since OpenBSD
2.7.
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.