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BIO_CTRL(3) | Library Functions Manual | 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_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 int
BIO_info_cb
(BIO
*b, int state,
int res);
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 a 0 if they do not recognize the
BIO_ctrl
() operation.
SEE ALSO
BIO_meth_new(3), BIO_new(3)HISTORY
BIO_ctrl
(),
BIO_reset
(),
BIO_flush
(),
BIO_eof
(),
BIO_set_close
(),
BIO_get_close
(), and
BIO_pending
() first appeared in SSLeay
0.6.0. BIO_wpending
() first appeared in
SSLeay 0.8.1. 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 ofBIO_seek
() on a file BIO for a successful
operation.August 18, 2022 | Debian |