Update build for OpenSSL-0.9.8j upgrade.
[dragonfly.git] / secure / lib / libcrypto / man / BIO_push.3
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132.\" ========================================================================
133.\"
134.IX Title "BIO_push 3"
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135.TH BIO_push 3 "2009-01-11" "0.9.8j" "OpenSSL"
136.\" For nroff, turn off justification. Always turn off hyphenation; it makes
137.\" way too many mistakes in technical documents.
138.if n .ad l
139.nh
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140.SH "NAME"
141BIO_push, BIO_pop \- add and remove BIOs from a chain.
142.SH "SYNOPSIS"
8b0cefbb 143.IX Header "SYNOPSIS"
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144.Vb 1
145\& #include <openssl/bio.h>
e257b235 146\&
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147\& BIO * BIO_push(BIO *b,BIO *append);
148\& BIO * BIO_pop(BIO *b);
149.Ve
150.SH "DESCRIPTION"
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151.IX Header "DESCRIPTION"
152The \fIBIO_push()\fR function appends the \s-1BIO\s0 \fBappend\fR to \fBb\fR, it returns
153\&\fBb\fR.
984263bc 154.PP
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155\&\fIBIO_pop()\fR removes the \s-1BIO\s0 \fBb\fR from a chain and returns the next \s-1BIO\s0
156in the chain, or \s-1NULL\s0 if there is no next \s-1BIO\s0. The removed \s-1BIO\s0 then
157becomes a single \s-1BIO\s0 with no association with the original chain,
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158it can thus be freed or attached to a different chain.
159.SH "NOTES"
8b0cefbb 160.IX Header "NOTES"
984263bc 161The names of these functions are perhaps a little misleading. \fIBIO_push()\fR
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162joins two \s-1BIO\s0 chains whereas \fIBIO_pop()\fR deletes a single \s-1BIO\s0 from a chain,
163the deleted \s-1BIO\s0 does not need to be at the end of a chain.
984263bc 164.PP
8b0cefbb 165The process of calling \fIBIO_push()\fR and \fIBIO_pop()\fR on a \s-1BIO\s0 may have additional
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166consequences (a control call is made to the affected BIOs) any effects will
167be noted in the descriptions of individual BIOs.
168.SH "EXAMPLES"
8b0cefbb 169.IX Header "EXAMPLES"
984263bc 170For these examples suppose \fBmd1\fR and \fBmd2\fR are digest BIOs, \fBb64\fR is
8b0cefbb 171a base64 \s-1BIO\s0 and \fBf\fR is a file \s-1BIO\s0.
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172.PP
173If the call:
174.PP
175.Vb 1
176\& BIO_push(b64, f);
177.Ve
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178.PP
179is made then the new chain will be \fBb64\-chain\fR. After making the calls
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180.PP
181.Vb 2
182\& BIO_push(md2, b64);
183\& BIO_push(md1, md2);
184.Ve
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185.PP
186the new chain is \fBmd1\-md2\-b64\-f\fR. Data written to \fBmd1\fR will be digested
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187by \fBmd1\fR and \fBmd2\fR, \fBbase64\fR encoded and written to \fBf\fR.
188.PP
189It should be noted that reading causes data to pass in the reverse
190direction, that is data is read from \fBf\fR, base64 \fBdecoded\fR and digested
191by \fBmd1\fR and \fBmd2\fR. If the call:
192.PP
193.Vb 1
194\& BIO_pop(md2);
195.Ve
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196.PP
197The call will return \fBb64\fR and the new chain will be \fBmd1\-b64\-f\fR data can
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198be written to \fBmd1\fR as before.
199.SH "RETURN VALUES"
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200.IX Header "RETURN VALUES"
201\&\fIBIO_push()\fR returns the end of the chain, \fBb\fR.
984263bc 202.PP
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203\&\fIBIO_pop()\fR returns the next \s-1BIO\s0 in the chain, or \s-1NULL\s0 if there is no next
204\&\s-1BIO\s0.
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205.SH "SEE ALSO"
206.IX Header "SEE ALSO"
8b0cefbb 207\&\s-1TBA\s0