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
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);
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.
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
resets a file related BIO's (that is file descriptor and FILE
BIOs) file position pointer to ofs
bytes from start of file.
returns the current file position of a file related BIO.
normally writes out any internally buffered data, in some
cases it is used to signal EOF and that no more data will be written.
returns 1 if the BIO has read EOF, the precise meaning of
"EOF" varies according to the BIO type.
sets the BIO b
close flag to 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.
returns the BIOs close flag.
return the number of pending characters in the BIOs
read and write buffers. Not all BIOs support these calls.
return a size_t type
and are functions, BIO_pending()
which call BIO_ctrl()
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.
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.
returns 1 for success and 0 or -1 for failure.
returns 1 if EOF has been reached 0 otherwise.
always returns 1.
returns the close flag value: BIO_CLOSE or BIO_NOCLOSE.
return the amount of pending data.
, 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()
call should be used and appropriate action taken
is the call fails.
The return values of BIO_pending()
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()
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
on a file BIO for a successful operation.