- update OpenSSL to 0.9.8
[dragonfly.git] / secure / lib / libcrypto / man / BIO_set_callback.3
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129.\" ========================================================================
130.\"
131.IX Title "BIO_set_callback 3"
a561f9ff 132.TH BIO_set_callback 3 "2005-07-06" "0.9.8" "OpenSSL"
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133.SH "NAME"
134BIO_set_callback, BIO_get_callback, BIO_set_callback_arg, BIO_get_callback_arg,
74dab6c2 135BIO_debug_callback \- BIO callback functions
984263bc 136.SH "SYNOPSIS"
8b0cefbb 137.IX Header "SYNOPSIS"
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138.Vb 1
139\& #include <openssl/bio.h>
140.Ve
8b0cefbb 141.PP
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142.Vb 4
143\& #define BIO_set_callback(b,cb) ((b)->callback=(cb))
144\& #define BIO_get_callback(b) ((b)->callback)
145\& #define BIO_set_callback_arg(b,arg) ((b)->cb_arg=(char *)(arg))
146\& #define BIO_get_callback_arg(b) ((b)->cb_arg)
147.Ve
8b0cefbb 148.PP
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149.Vb 2
150\& long BIO_debug_callback(BIO *bio,int cmd,const char *argp,int argi,
151\& long argl,long ret);
152.Ve
8b0cefbb 153.PP
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154.Vb 2
155\& typedef long callback(BIO *b, int oper, const char *argp,
156\& int argi, long argl, long retvalue);
157.Ve
158.SH "DESCRIPTION"
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159.IX Header "DESCRIPTION"
160\&\fIBIO_set_callback()\fR and \fIBIO_get_callback()\fR set and retrieve the \s-1BIO\s0 callback,
161they are both macros. The callback is called during most high level \s-1BIO\s0
984263bc 162operations. It can be used for debugging purposes to trace operations on
8b0cefbb 163a \s-1BIO\s0 or to modify its operation.
984263bc 164.PP
8b0cefbb 165\&\fIBIO_set_callback_arg()\fR and \fIBIO_get_callback_arg()\fR are macros which can be
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166used to set and retrieve an argument for use in the callback.
167.PP
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168\&\fIBIO_debug_callback()\fR is a standard debugging callback which prints
169out information relating to each \s-1BIO\s0 operation. If the callback
170argument is set if is interpreted as a \s-1BIO\s0 to send the information
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171to, otherwise stderr is used.
172.PP
8b0cefbb 173\&\fIcallback()\fR is the callback function itself. The meaning of each
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174argument is described below.
175.PP
8b0cefbb 176The \s-1BIO\s0 the callback is attached to is passed in \fBb\fR.
984263bc 177.PP
8b0cefbb 178\&\fBoper\fR is set to the operation being performed. For some operations
984263bc 179the callback is called twice, once before and once after the actual
8b0cefbb 180operation, the latter case has \fBoper\fR or'ed with \s-1BIO_CB_RETURN\s0.
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181.PP
182The meaning of the arguments \fBargp\fR, \fBargi\fR and \fBargl\fR depends on
183the value of \fBoper\fR, that is the operation being performed.
184.PP
8b0cefbb 185\&\fBretvalue\fR is the return value that would be returned to the
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186application if no callback were present. The actual value returned
187is the return value of the callback itself. In the case of callbacks
8b0cefbb 188called before the actual \s-1BIO\s0 operation 1 is placed in retvalue, if
984263bc 189the return value is not positive it will be immediately returned to
8b0cefbb 190the application and the \s-1BIO\s0 operation will not be performed.
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191.PP
192The callback should normally simply return \fBretvalue\fR when it has
193finished processing, unless if specifically wishes to modify the
194value returned to the application.
195.SH "CALLBACK OPERATIONS"
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196.IX Header "CALLBACK OPERATIONS"
197.IP "\fBBIO_free(b)\fR" 4
198.IX Item "BIO_free(b)"
199callback(b, \s-1BIO_CB_FREE\s0, \s-1NULL\s0, 0L, 0L, 1L) is called before the
984263bc 200free operation.
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201.IP "\fBBIO_read(b, out, outl)\fR" 4
202.IX Item "BIO_read(b, out, outl)"
203callback(b, \s-1BIO_CB_READ\s0, out, outl, 0L, 1L) is called before
204the read and callback(b, BIO_CB_READ|BIO_CB_RETURN, out, outl, 0L, retvalue)
984263bc 205after.
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206.IP "\fBBIO_write(b, in, inl)\fR" 4
207.IX Item "BIO_write(b, in, inl)"
208callback(b, \s-1BIO_CB_WRITE\s0, in, inl, 0L, 1L) is called before
209the write and callback(b, BIO_CB_WRITE|BIO_CB_RETURN, in, inl, 0L, retvalue)
984263bc 210after.
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211.IP "\fBBIO_gets(b, out, outl)\fR" 4
212.IX Item "BIO_gets(b, out, outl)"
213callback(b, \s-1BIO_CB_GETS\s0, out, outl, 0L, 1L) is called before
214the operation and callback(b, BIO_CB_GETS|BIO_CB_RETURN, out, outl, 0L, retvalue)
984263bc 215after.
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216.IP "\fBBIO_puts(b, in)\fR" 4
217.IX Item "BIO_puts(b, in)"
218callback(b, \s-1BIO_CB_WRITE\s0, in, 0, 0L, 1L) is called before
219the operation and callback(b, BIO_CB_WRITE|BIO_CB_RETURN, in, 0, 0L, retvalue)
984263bc 220after.
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221.IP "\fBBIO_ctrl(\s-1BIO\s0 *b, int cmd, long larg, void *parg)\fR" 4
222.IX Item "BIO_ctrl(BIO *b, int cmd, long larg, void *parg)"
223callback(b,BIO_CB_CTRL,parg,cmd,larg,1L) is called before the call and
224callback(b,BIO_CB_CTRL|BIO_CB_RETURN,parg,cmd, larg,ret) after.
984263bc 225.SH "EXAMPLE"
8b0cefbb 226.IX Header "EXAMPLE"
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227The \fIBIO_debug_callback()\fR function is a good example, its source is
228in crypto/bio/bio_cb.c
229.SH "SEE ALSO"
230.IX Header "SEE ALSO"
8b0cefbb 231\&\s-1TBA\s0