.\" Automatically generated by Pod::Man 2.16 (Pod::Simple 3.05)
.\"
.\" Standard preamble:
.\" ========================================================================
.de Sh \" Subsection heading
.br
.if t .Sp
.ne 5
.PP
\fB\\$1\fR
.PP
..
.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
..
.\" Set up some character translations and predefined strings.  \*(-- will
.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
.\" double quote, and \*(R" will give a right double quote.  \*(C+ will
.\" give a nicer C++.  Capital omega is used to do unbreakable dashes and
.\" therefore won't be available.  \*(C` and \*(C' expand to `' in nroff,
.\" nothing in troff, for use with C<>.
.tr \(*W-
.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
.ie n \{\
.    ds -- \(*W-
.    ds PI pi
.    if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
.    if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\"  diablo 12 pitch
.    ds L" ""
.    ds R" ""
.    ds C` ""
.    ds C' ""
'br\}
.el\{\
.    ds -- \|\(em\|
.    ds PI \(*p
.    ds L" ``
.    ds R" ''
'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 turned on, we'll generate index entries on stderr for
.\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index
.\" entries marked with X<> in POD.  Of course, you'll have to process the
.\" output yourself in some meaningful fashion.
.ie \nF \{\
.    de IX
.    tm Index:\\$1\t\\n%\t"\\$2"
..
.    nr % 0
.    rr F
.\}
.el \{\
.    de IX
..
.\}
.\"
.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
.\" Fear.  Run.  Save yourself.  No user-serviceable parts.
.    \" fudge factors for nroff and troff
.if n \{\
.    ds #H 0
.    ds #V .8m
.    ds #F .3m
.    ds #[ \f1
.    ds #] \fP
.\}
.if t \{\
.    ds #H ((1u-(\\\\n(.fu%2u))*.13m)
.    ds #V .6m
.    ds #F 0
.    ds #[ \&
.    ds #] \&
.\}
.    \" simple accents for nroff and troff
.if n \{\
.    ds ' \&
.    ds ` \&
.    ds ^ \&
.    ds , \&
.    ds ~ ~
.    ds /
.\}
.if t \{\
.    ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
.    ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
.    ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
.    ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
.    ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
.    ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
.\}
.    \" troff and (daisy-wheel) nroff accents
.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
.ds 8 \h'\*(#H'\(*b\h'-\*(#H'
.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
.ds ae a\h'-(\w'a'u*4/10)'e
.ds Ae A\h'-(\w'A'u*4/10)'E
.    \" corrections for vroff
.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
.    \" for low resolution devices (crt and lpr)
.if \n(.H>23 .if \n(.V>19 \
\{\
.    ds : e
.    ds 8 ss
.    ds o a
.    ds d- d\h'-1'\(ga
.    ds D- D\h'-1'\(hy
.    ds th \o'bp'
.    ds Th \o'LP'
.    ds ae ae
.    ds Ae AE
.\}
.rm #[ #] #H #V #F C
.\" ========================================================================
.\"
.IX Title "BIO_push 3"
.TH BIO_push 3 "2009-04-11" "0.9.8k" "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_push, BIO_pop \- add and remove BIOs from a chain.
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/bio.h>
\&
\& BIO *  BIO_push(BIO *b,BIO *append);
\& BIO *  BIO_pop(BIO *b);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \fIBIO_push()\fR function appends the \s-1BIO\s0 \fBappend\fR to \fBb\fR, it returns
\&\fBb\fR.
.PP
\&\fIBIO_pop()\fR removes the \s-1BIO\s0 \fBb\fR from a chain and returns the next \s-1BIO\s0
in the chain, or \s-1NULL\s0 if there is no next \s-1BIO\s0. The removed \s-1BIO\s0 then
becomes a single \s-1BIO\s0 with no association with the original chain,
it can thus be freed or attached to a different chain.
.SH "NOTES"
.IX Header "NOTES"
The names of these functions are perhaps a little misleading. \fIBIO_push()\fR
joins two \s-1BIO\s0 chains whereas \fIBIO_pop()\fR deletes a single \s-1BIO\s0 from a chain,
the deleted \s-1BIO\s0 does not need to be at the end of a chain.
.PP
The process of calling \fIBIO_push()\fR and \fIBIO_pop()\fR on a \s-1BIO\s0 may have additional
consequences (a control call is made to the affected BIOs) any effects will
be noted in the descriptions of individual BIOs.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
For these examples suppose \fBmd1\fR and \fBmd2\fR are digest BIOs, \fBb64\fR is
a base64 \s-1BIO\s0 and \fBf\fR is a file \s-1BIO\s0.
.PP
If the call:
.PP
.Vb 1
\& BIO_push(b64, f);
.Ve
.PP
is made then the new chain will be \fBb64\-chain\fR. After making the calls
.PP
.Vb 2
\& BIO_push(md2, b64);
\& BIO_push(md1, md2);
.Ve
.PP
the new chain is \fBmd1\-md2\-b64\-f\fR. Data written to \fBmd1\fR will be digested
by \fBmd1\fR and \fBmd2\fR, \fBbase64\fR encoded and written to \fBf\fR.
.PP
It should be noted that reading causes data to pass in the reverse
direction, that is data is read from \fBf\fR, base64 \fBdecoded\fR and digested
by \fBmd1\fR and \fBmd2\fR. If the call:
.PP
.Vb 1
\& BIO_pop(md2);
.Ve
.PP
The call will return \fBb64\fR and the new chain will be \fBmd1\-b64\-f\fR data can
be written to \fBmd1\fR as before.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fIBIO_push()\fR returns the end of the chain, \fBb\fR.
.PP
\&\fIBIO_pop()\fR returns the next \s-1BIO\s0 in the chain, or \s-1NULL\s0 if there is no next
\&\s-1BIO\s0.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\s-1TBA\s0