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 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, 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
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().
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 structure's internal buffers but it is not
possible to determine this in a portably 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.
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.