Local adjustments for OpenSSL-1.0.1p.
[dragonfly.git] / secure / lib / libcrypto / man / BIO_push.3
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133.\" ========================================================================
134.\"
135.IX Title "BIO_push 3"
7dc78669 136.TH BIO_push 3 "2015-07-09" "1.0.1p" "OpenSSL"
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137.\" For nroff, turn off justification. Always turn off hyphenation; it makes
138.\" way too many mistakes in technical documents.
139.if n .ad l
140.nh
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141.SH "NAME"
142BIO_push, BIO_pop \- add and remove BIOs from a chain.
143.SH "SYNOPSIS"
8b0cefbb 144.IX Header "SYNOPSIS"
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145.Vb 1
146\& #include <openssl/bio.h>
e257b235 147\&
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148\& BIO * BIO_push(BIO *b,BIO *append);
149\& BIO * BIO_pop(BIO *b);
150.Ve
151.SH "DESCRIPTION"
8b0cefbb 152.IX Header "DESCRIPTION"
5a44c043 153The \fIBIO_push()\fR function appends the \s-1BIO \s0\fBappend\fR to \fBb\fR, it returns
8b0cefbb 154\&\fBb\fR.
984263bc 155.PP
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156\&\fIBIO_pop()\fR removes the \s-1BIO \s0\fBb\fR from a chain and returns the next \s-1BIO\s0
157in the chain, or \s-1NULL\s0 if there is no next \s-1BIO.\s0 The removed \s-1BIO\s0 then
8b0cefbb 158becomes a single \s-1BIO\s0 with no association with the original chain,
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159it can thus be freed or attached to a different chain.
160.SH "NOTES"
8b0cefbb 161.IX Header "NOTES"
984263bc 162The names of these functions are perhaps a little misleading. \fIBIO_push()\fR
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163joins two \s-1BIO\s0 chains whereas \fIBIO_pop()\fR deletes a single \s-1BIO\s0 from a chain,
164the deleted \s-1BIO\s0 does not need to be at the end of a chain.
984263bc 165.PP
8b0cefbb 166The process of calling \fIBIO_push()\fR and \fIBIO_pop()\fR on a \s-1BIO\s0 may have additional
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167consequences (a control call is made to the affected BIOs) any effects will
168be noted in the descriptions of individual BIOs.
169.SH "EXAMPLES"
8b0cefbb 170.IX Header "EXAMPLES"
984263bc 171For these examples suppose \fBmd1\fR and \fBmd2\fR are digest BIOs, \fBb64\fR is
5a44c043 172a base64 \s-1BIO\s0 and \fBf\fR is a file \s-1BIO.\s0
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173.PP
174If the call:
175.PP
176.Vb 1
177\& BIO_push(b64, f);
178.Ve
8b0cefbb 179.PP
ecf90583 180is made then the new chain will be \fBb64\-f\fR. After making the calls
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181.PP
182.Vb 2
183\& BIO_push(md2, b64);
184\& BIO_push(md1, md2);
185.Ve
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186.PP
187the new chain is \fBmd1\-md2\-b64\-f\fR. Data written to \fBmd1\fR will be digested
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188by \fBmd1\fR and \fBmd2\fR, \fBbase64\fR encoded and written to \fBf\fR.
189.PP
190It should be noted that reading causes data to pass in the reverse
191direction, that is data is read from \fBf\fR, base64 \fBdecoded\fR and digested
192by \fBmd1\fR and \fBmd2\fR. If the call:
193.PP
194.Vb 1
195\& BIO_pop(md2);
196.Ve
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197.PP
198The call will return \fBb64\fR and the new chain will be \fBmd1\-b64\-f\fR data can
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199be written to \fBmd1\fR as before.
200.SH "RETURN VALUES"
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201.IX Header "RETURN VALUES"
202\&\fIBIO_push()\fR returns the end of the chain, \fBb\fR.
984263bc 203.PP
8b0cefbb 204\&\fIBIO_pop()\fR returns the next \s-1BIO\s0 in the chain, or \s-1NULL\s0 if there is no next
5a44c043 205\&\s-1BIO.\s0
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206.SH "SEE ALSO"
207.IX Header "SEE ALSO"
8b0cefbb 208\&\s-1TBA\s0