Merge branch 'vendor/BINUTILS220' into bu220
[dragonfly.git] / secure / lib / libcrypto / man / BIO_set_callback.3
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132.\" ========================================================================
133.\"
134.IX Title "BIO_set_callback 3"
405d0527 135.TH BIO_set_callback 3 "2009-04-11" "0.9.8k" "OpenSSL"
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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_set_callback, BIO_get_callback, BIO_set_callback_arg, BIO_get_callback_arg,
74dab6c2 142BIO_debug_callback \- BIO callback functions
984263bc 143.SH "SYNOPSIS"
8b0cefbb 144.IX Header "SYNOPSIS"
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145.Vb 1
146\& #include <openssl/bio.h>
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147\&
148\& #define BIO_set_callback(b,cb) ((b)\->callback=(cb))
149\& #define BIO_get_callback(b) ((b)\->callback)
150\& #define BIO_set_callback_arg(b,arg) ((b)\->cb_arg=(char *)(arg))
151\& #define BIO_get_callback_arg(b) ((b)\->cb_arg)
152\&
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153\& long BIO_debug_callback(BIO *bio,int cmd,const char *argp,int argi,
154\& long argl,long ret);
e257b235 155\&
edae4a78 156\& typedef long (*callback)(BIO *b, int oper, const char *argp,
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157\& int argi, long argl, long retvalue);
158.Ve
159.SH "DESCRIPTION"
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160.IX Header "DESCRIPTION"
161\&\fIBIO_set_callback()\fR and \fIBIO_get_callback()\fR set and retrieve the \s-1BIO\s0 callback,
162they are both macros. The callback is called during most high level \s-1BIO\s0
984263bc 163operations. It can be used for debugging purposes to trace operations on
8b0cefbb 164a \s-1BIO\s0 or to modify its operation.
984263bc 165.PP
8b0cefbb 166\&\fIBIO_set_callback_arg()\fR and \fIBIO_get_callback_arg()\fR are macros which can be
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167used to set and retrieve an argument for use in the callback.
168.PP
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169\&\fIBIO_debug_callback()\fR is a standard debugging callback which prints
170out information relating to each \s-1BIO\s0 operation. If the callback
171argument is set if is interpreted as a \s-1BIO\s0 to send the information
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172to, otherwise stderr is used.
173.PP
8b0cefbb 174\&\fIcallback()\fR is the callback function itself. The meaning of each
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175argument is described below.
176.PP
8b0cefbb 177The \s-1BIO\s0 the callback is attached to is passed in \fBb\fR.
984263bc 178.PP
8b0cefbb 179\&\fBoper\fR is set to the operation being performed. For some operations
984263bc 180the callback is called twice, once before and once after the actual
8b0cefbb 181operation, the latter case has \fBoper\fR or'ed with \s-1BIO_CB_RETURN\s0.
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182.PP
183The meaning of the arguments \fBargp\fR, \fBargi\fR and \fBargl\fR depends on
184the value of \fBoper\fR, that is the operation being performed.
185.PP
8b0cefbb 186\&\fBretvalue\fR is the return value that would be returned to the
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187application if no callback were present. The actual value returned
188is the return value of the callback itself. In the case of callbacks
8b0cefbb 189called before the actual \s-1BIO\s0 operation 1 is placed in retvalue, if
984263bc 190the return value is not positive it will be immediately returned to
8b0cefbb 191the application and the \s-1BIO\s0 operation will not be performed.
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192.PP
193The callback should normally simply return \fBretvalue\fR when it has
194finished processing, unless if specifically wishes to modify the
195value returned to the application.
196.SH "CALLBACK OPERATIONS"
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197.IX Header "CALLBACK OPERATIONS"
198.IP "\fBBIO_free(b)\fR" 4
199.IX Item "BIO_free(b)"
200callback(b, \s-1BIO_CB_FREE\s0, \s-1NULL\s0, 0L, 0L, 1L) is called before the
984263bc 201free operation.
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202.IP "\fBBIO_read(b, out, outl)\fR" 4
203.IX Item "BIO_read(b, out, outl)"
204callback(b, \s-1BIO_CB_READ\s0, out, outl, 0L, 1L) is called before
205the read and callback(b, BIO_CB_READ|BIO_CB_RETURN, out, outl, 0L, retvalue)
984263bc 206after.
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207.IP "\fBBIO_write(b, in, inl)\fR" 4
208.IX Item "BIO_write(b, in, inl)"
209callback(b, \s-1BIO_CB_WRITE\s0, in, inl, 0L, 1L) is called before
210the write and callback(b, BIO_CB_WRITE|BIO_CB_RETURN, in, inl, 0L, retvalue)
984263bc 211after.
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212.IP "\fBBIO_gets(b, out, outl)\fR" 4
213.IX Item "BIO_gets(b, out, outl)"
214callback(b, \s-1BIO_CB_GETS\s0, out, outl, 0L, 1L) is called before
215the operation and callback(b, BIO_CB_GETS|BIO_CB_RETURN, out, outl, 0L, retvalue)
984263bc 216after.
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217.IP "\fBBIO_puts(b, in)\fR" 4
218.IX Item "BIO_puts(b, in)"
219callback(b, \s-1BIO_CB_WRITE\s0, in, 0, 0L, 1L) is called before
220the operation and callback(b, BIO_CB_WRITE|BIO_CB_RETURN, in, 0, 0L, retvalue)
984263bc 221after.
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222.IP "\fBBIO_ctrl(\s-1BIO\s0 *b, int cmd, long larg, void *parg)\fR" 4
223.IX Item "BIO_ctrl(BIO *b, int cmd, long larg, void *parg)"
224callback(b,BIO_CB_CTRL,parg,cmd,larg,1L) is called before the call and
225callback(b,BIO_CB_CTRL|BIO_CB_RETURN,parg,cmd, larg,ret) after.
984263bc 226.SH "EXAMPLE"
8b0cefbb 227.IX Header "EXAMPLE"
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228The \fIBIO_debug_callback()\fR function is a good example, its source is
229in crypto/bio/bio_cb.c
230.SH "SEE ALSO"
231.IX Header "SEE ALSO"
8b0cefbb 232\&\s-1TBA\s0