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_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);
DESCRIPTIONBIO_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
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
characters 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
functions, BIO_pending() and BIO_wpending() are macros
which call BIO_ctrl().
RETURN VALUESBIO_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.
NOTESBIO_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 particular
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 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.
SEE ALSO
TBA
18/Sep/2000 0.9.6j BIO_ctrl(3)
