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.TH BIO_ctrl 3 "0.9.7d" "2/Sep/2004" "OpenSSL"
.UC
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.rm #[ #] #H #V #F C
.SH "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
.SH "SYNOPSIS"
.PP
.Vb 1
\& #include <openssl/bio.h>
.Ve
.Vb 4
\& 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);
.Ve
.Vb 11
\& 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);
.Ve
.Vb 2
\& int BIO_get_info_callback(BIO *b,bio_info_cb **cbp);
\& int BIO_set_info_callback(BIO *b,bio_info_cb *cb);
.Ve
.Vb 1
\& typedef void bio_info_cb(BIO *b, int oper, const char *ptr, int arg1, long arg2, long arg3);
.Ve
.SH "DESCRIPTION"
\fIBIO_ctrl()\fR, \fIBIO_callback_ctrl()\fR, \fIBIO_ptr_ctrl()\fR and \fIBIO_int_ctrl()\fR
are BIO \*(L"control\*(R" 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.
.PP
\fIBIO_reset()\fR 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.
.PP
\fIBIO_seek()\fR resets a file related BIO's (that is file descriptor and
FILE BIOs) file position pointer to \fBofs\fR bytes from start of file.
.PP
\fIBIO_tell()\fR returns the current file position of a file related BIO.
.PP
\fIBIO_flush()\fR normally writes out any internally buffered data, in some
cases it is used to signal EOF and that no more data will be written.
.PP
\fIBIO_eof()\fR returns 1 if the BIO has read EOF, the precise meaning of
\*(L"EOF\*(R" varies according to the BIO type.
.PP
\fIBIO_set_close()\fR sets the BIO \fBb\fR close flag to \fBflag\fR. \fBflag\fR 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.
.PP
\fIBIO_get_close()\fR returns the BIOs close flag.
.PP
\fIBIO_pending()\fR, \fIBIO_ctrl_pending()\fR, \fIBIO_wpending()\fR and \fIBIO_ctrl_wpending()\fR
return the number of pending characters in the BIOs read and write buffers.
Not all BIOs support these calls. \fIBIO_ctrl_pending()\fR and \fIBIO_ctrl_wpending()\fR
return a size_t type and are functions, \fIBIO_pending()\fR and \fIBIO_wpending()\fR are
macros which call \fIBIO_ctrl()\fR.
.SH "RETURN VALUES"
\fIBIO_reset()\fR 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.
.PP
\fIBIO_seek()\fR and \fIBIO_tell()\fR both return the current file position on success
and \-1 for failure, except file BIOs which for \fIBIO_seek()\fR always return 0
for success and \-1 for failure.
.PP
\fIBIO_flush()\fR returns 1 for success and 0 or \-1 for failure.
.PP
\fIBIO_eof()\fR returns 1 if EOF has been reached 0 otherwise.
.PP
\fIBIO_set_close()\fR always returns 1.
.PP
\fIBIO_get_close()\fR returns the close flag value: BIO_CLOSE or BIO_NOCLOSE.
.PP
\fIBIO_pending()\fR, \fIBIO_ctrl_pending()\fR, \fIBIO_wpending()\fR and \fIBIO_ctrl_wpending()\fR
return the amount of pending data.
.SH "NOTES"
\fIBIO_flush()\fR, because it can write data may return 0 or \-1 indicating
that the call should be retried later in a similar manner to \fIBIO_write()\fR. 
The \fIBIO_should_retry()\fR call should be used and appropriate action taken
is the call fails.
.PP
The return values of \fIBIO_pending()\fR and \fIBIO_wpending()\fR 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.
.PP
Filter BIOs if they do not internally handle a particular \fIBIO_ctrl()\fR
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
\fIBIO_seek()\fR, but this may still succeed if the chain ends in a FILE
or file descriptor BIO.
.PP
Source/sink BIOs return an 0 if they do not recognize the \fIBIO_ctrl()\fR
operation.
.SH "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 \fIBIO_seek()\fR on a file BIO for a successful operation. 
.SH "SEE ALSO"
TBA

.rn }` ''
.IX Title "BIO_ctrl 3"
.IX 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"

.IX Header "NAME"

.IX Header "SYNOPSIS"

.IX Header "DESCRIPTION"

.IX Header "RETURN VALUES"

.IX Header "NOTES"

.IX Header "BUGS"

.IX Header "SEE ALSO"