Update files for OpenSSL-1.0.0f import.
[dragonfly.git] / secure / lib / libcrypto / man / BIO_push.3
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124.\" ========================================================================
125.\"
126.IX Title "BIO_push 3"
e3261593 127.TH BIO_push 3 "2012-01-04" "1.0.0f" "OpenSSL"
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128.\" For nroff, turn off justification. Always turn off hyphenation; it makes
129.\" way too many mistakes in technical documents.
130.if n .ad l
131.nh
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132.SH "NAME"
133BIO_push, BIO_pop \- add and remove BIOs from a chain.
134.SH "SYNOPSIS"
8b0cefbb 135.IX Header "SYNOPSIS"
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136.Vb 1
137\& #include <openssl/bio.h>
e257b235 138\&
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139\& BIO * BIO_push(BIO *b,BIO *append);
140\& BIO * BIO_pop(BIO *b);
141.Ve
142.SH "DESCRIPTION"
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143.IX Header "DESCRIPTION"
144The \fIBIO_push()\fR function appends the \s-1BIO\s0 \fBappend\fR to \fBb\fR, it returns
145\&\fBb\fR.
984263bc 146.PP
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147\&\fIBIO_pop()\fR removes the \s-1BIO\s0 \fBb\fR from a chain and returns the next \s-1BIO\s0
148in the chain, or \s-1NULL\s0 if there is no next \s-1BIO\s0. The removed \s-1BIO\s0 then
149becomes a single \s-1BIO\s0 with no association with the original chain,
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150it can thus be freed or attached to a different chain.
151.SH "NOTES"
8b0cefbb 152.IX Header "NOTES"
984263bc 153The names of these functions are perhaps a little misleading. \fIBIO_push()\fR
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154joins two \s-1BIO\s0 chains whereas \fIBIO_pop()\fR deletes a single \s-1BIO\s0 from a chain,
155the deleted \s-1BIO\s0 does not need to be at the end of a chain.
984263bc 156.PP
8b0cefbb 157The process of calling \fIBIO_push()\fR and \fIBIO_pop()\fR on a \s-1BIO\s0 may have additional
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158consequences (a control call is made to the affected BIOs) any effects will
159be noted in the descriptions of individual BIOs.
160.SH "EXAMPLES"
8b0cefbb 161.IX Header "EXAMPLES"
984263bc 162For these examples suppose \fBmd1\fR and \fBmd2\fR are digest BIOs, \fBb64\fR is
8b0cefbb 163a base64 \s-1BIO\s0 and \fBf\fR is a file \s-1BIO\s0.
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164.PP
165If the call:
166.PP
167.Vb 1
168\& BIO_push(b64, f);
169.Ve
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170.PP
171is made then the new chain will be \fBb64\-chain\fR. After making the calls
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172.PP
173.Vb 2
174\& BIO_push(md2, b64);
175\& BIO_push(md1, md2);
176.Ve
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177.PP
178the new chain is \fBmd1\-md2\-b64\-f\fR. Data written to \fBmd1\fR will be digested
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179by \fBmd1\fR and \fBmd2\fR, \fBbase64\fR encoded and written to \fBf\fR.
180.PP
181It should be noted that reading causes data to pass in the reverse
182direction, that is data is read from \fBf\fR, base64 \fBdecoded\fR and digested
183by \fBmd1\fR and \fBmd2\fR. If the call:
184.PP
185.Vb 1
186\& BIO_pop(md2);
187.Ve
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188.PP
189The call will return \fBb64\fR and the new chain will be \fBmd1\-b64\-f\fR data can
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190be written to \fBmd1\fR as before.
191.SH "RETURN VALUES"
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192.IX Header "RETURN VALUES"
193\&\fIBIO_push()\fR returns the end of the chain, \fBb\fR.
984263bc 194.PP
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195\&\fIBIO_pop()\fR returns the next \s-1BIO\s0 in the chain, or \s-1NULL\s0 if there is no next
196\&\s-1BIO\s0.
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197.SH "SEE ALSO"
198.IX Header "SEE ALSO"
8b0cefbb 199\&\s-1TBA\s0