.\" -*- mode: troff; coding: utf-8 -*-
.\" Automatically generated by Pod::Man 5.01 (Pod::Simple 3.43)
.\"
.\" Standard preamble:
.\" ========================================================================
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Vb \" Begin verbatim text
.ft CW
.nf
.ne \\$1
..
.de Ve \" End verbatim text
.ft R
.fi
..
.\" \*(C` and \*(C' are quotes in nroff, nothing in troff, for use with C<>.
.ie n \{\
.    ds C` ""
.    ds C' ""
'br\}
.el\{\
.    ds C`
.    ds C'
'br\}
.\"
.\" Escape single quotes in literal strings from groff's Unicode transform.
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\"
.\" If the F register is >0, we'll generate index entries on stderr for
.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
.\" entries marked with X<> in POD.  Of course, you'll have to process the
.\" output yourself in some meaningful fashion.
.\"
.\" Avoid warning from groff about undefined register 'F'.
.de IX
..
.nr rF 0
.if \n(.g .if rF .nr rF 1
.if (\n(rF:(\n(.g==0)) \{\
.    if \nF \{\
.        de IX
.        tm Index:\\$1\t\\n%\t"\\$2"
..
.        if !\nF==2 \{\
.            nr % 0
.            nr F 2
.        \}
.    \}
.\}
.rr rF
.\" ========================================================================
.\"
.IX Title "BIO_ctrl 3"
.TH BIO_ctrl 3 2019-12-20 1.0.2u OpenSSL
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.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
.IX Header "SYNOPSIS"
.Vb 1
\& #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);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\fBBIO_ctrl()\fR, \fBBIO_callback_ctrl()\fR, \fBBIO_ptr_ctrl()\fR and \fBBIO_int_ctrl()\fR
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.
.PP
\&\fBBIO_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
\&\fBBIO_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
\&\fBBIO_tell()\fR returns the current file position of a file related BIO.
.PP
\&\fBBIO_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
\&\fBBIO_eof()\fR returns 1 if the BIO has read EOF, the precise meaning of
"EOF" varies according to the BIO type.
.PP
\&\fBBIO_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
\&\fBBIO_get_close()\fR returns the BIOs close flag.
.PP
\&\fBBIO_pending()\fR, \fBBIO_ctrl_pending()\fR, \fBBIO_wpending()\fR and \fBBIO_ctrl_wpending()\fR
return the number of pending characters in the BIOs read and write buffers.
Not all BIOs support these calls. \fBBIO_ctrl_pending()\fR and \fBBIO_ctrl_wpending()\fR
return a size_t type and are functions, \fBBIO_pending()\fR and \fBBIO_wpending()\fR are
macros which call \fBBIO_ctrl()\fR.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBBIO_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
\&\fBBIO_seek()\fR and \fBBIO_tell()\fR both return the current file position on success
and \-1 for failure, except file BIOs which for \fBBIO_seek()\fR always return 0
for success and \-1 for failure.
.PP
\&\fBBIO_flush()\fR returns 1 for success and 0 or \-1 for failure.
.PP
\&\fBBIO_eof()\fR returns 1 if EOF has been reached 0 otherwise.
.PP
\&\fBBIO_set_close()\fR always returns 1.
.PP
\&\fBBIO_get_close()\fR returns the close flag value: BIO_CLOSE or BIO_NOCLOSE.
.PP
\&\fBBIO_pending()\fR, \fBBIO_ctrl_pending()\fR, \fBBIO_wpending()\fR and \fBBIO_ctrl_wpending()\fR
return the amount of pending data.
.SH NOTES
.IX Header "NOTES"
\&\fBBIO_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 \fBBIO_write()\fR. 
The \fBBIO_should_retry()\fR call should be used and appropriate action taken
is the call fails.
.PP
The return values of \fBBIO_pending()\fR and \fBBIO_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 \fBBIO_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
\&\fBBIO_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 \fBBIO_ctrl()\fR
operation.
.SH BUGS
.IX Header "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 \fBBIO_seek()\fR on a file BIO for a successful operation.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
TBA