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| 132 | .\" ======================================================================== |
| 133 | .\" |
| 134 | .IX Title "BIO_set_callback 3" |
| 135 | .TH BIO_set_callback 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 |
| 140 | .SH "NAME" |
| 141 | BIO_set_callback, BIO_get_callback, BIO_set_callback_arg, BIO_get_callback_arg, |
| 142 | BIO_debug_callback \- BIO callback functions |
| 143 | .SH "SYNOPSIS" |
| 144 | .IX Header "SYNOPSIS" |
| 145 | .Vb 1 |
| 146 | \& #include <openssl/bio.h> |
| 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 | \& |
| 153 | \& long BIO_debug_callback(BIO *bio,int cmd,const char *argp,int argi, |
| 154 | \& long argl,long ret); |
| 155 | \& |
| 156 | \& typedef long (*callback)(BIO *b, int oper, const char *argp, |
| 157 | \& int argi, long argl, long retvalue); |
| 158 | .Ve |
| 159 | .SH "DESCRIPTION" |
| 160 | .IX Header "DESCRIPTION" |
| 161 | \&\fIBIO_set_callback()\fR and \fIBIO_get_callback()\fR set and retrieve the \s-1BIO\s0 callback, |
| 162 | they are both macros. The callback is called during most high level \s-1BIO\s0 |
| 163 | operations. It can be used for debugging purposes to trace operations on |
| 164 | a \s-1BIO\s0 or to modify its operation. |
| 165 | .PP |
| 166 | \&\fIBIO_set_callback_arg()\fR and \fIBIO_get_callback_arg()\fR are macros which can be |
| 167 | used to set and retrieve an argument for use in the callback. |
| 168 | .PP |
| 169 | \&\fIBIO_debug_callback()\fR is a standard debugging callback which prints |
| 170 | out information relating to each \s-1BIO\s0 operation. If the callback |
| 171 | argument is set if is interpreted as a \s-1BIO\s0 to send the information |
| 172 | to, otherwise stderr is used. |
| 173 | .PP |
| 174 | \&\fIcallback()\fR is the callback function itself. The meaning of each |
| 175 | argument is described below. |
| 176 | .PP |
| 177 | The \s-1BIO\s0 the callback is attached to is passed in \fBb\fR. |
| 178 | .PP |
| 179 | \&\fBoper\fR is set to the operation being performed. For some operations |
| 180 | the callback is called twice, once before and once after the actual |
| 181 | operation, the latter case has \fBoper\fR or'ed with \s-1BIO_CB_RETURN\s0. |
| 182 | .PP |
| 183 | The meaning of the arguments \fBargp\fR, \fBargi\fR and \fBargl\fR depends on |
| 184 | the value of \fBoper\fR, that is the operation being performed. |
| 185 | .PP |
| 186 | \&\fBretvalue\fR is the return value that would be returned to the |
| 187 | application if no callback were present. The actual value returned |
| 188 | is the return value of the callback itself. In the case of callbacks |
| 189 | called before the actual \s-1BIO\s0 operation 1 is placed in retvalue, if |
| 190 | the return value is not positive it will be immediately returned to |
| 191 | the application and the \s-1BIO\s0 operation will not be performed. |
| 192 | .PP |
| 193 | The callback should normally simply return \fBretvalue\fR when it has |
| 194 | finished processing, unless if specifically wishes to modify the |
| 195 | value returned to the application. |
| 196 | .SH "CALLBACK OPERATIONS" |
| 197 | .IX Header "CALLBACK OPERATIONS" |
| 198 | .IP "\fBBIO_free(b)\fR" 4 |
| 199 | .IX Item "BIO_free(b)" |
| 200 | callback(b, \s-1BIO_CB_FREE\s0, \s-1NULL\s0, 0L, 0L, 1L) is called before the |
| 201 | free operation. |
| 202 | .IP "\fBBIO_read(b, out, outl)\fR" 4 |
| 203 | .IX Item "BIO_read(b, out, outl)" |
| 204 | callback(b, \s-1BIO_CB_READ\s0, out, outl, 0L, 1L) is called before |
| 205 | the read and callback(b, BIO_CB_READ|BIO_CB_RETURN, out, outl, 0L, retvalue) |
| 206 | after. |
| 207 | .IP "\fBBIO_write(b, in, inl)\fR" 4 |
| 208 | .IX Item "BIO_write(b, in, inl)" |
| 209 | callback(b, \s-1BIO_CB_WRITE\s0, in, inl, 0L, 1L) is called before |
| 210 | the write and callback(b, BIO_CB_WRITE|BIO_CB_RETURN, in, inl, 0L, retvalue) |
| 211 | after. |
| 212 | .IP "\fBBIO_gets(b, out, outl)\fR" 4 |
| 213 | .IX Item "BIO_gets(b, out, outl)" |
| 214 | callback(b, \s-1BIO_CB_GETS\s0, out, outl, 0L, 1L) is called before |
| 215 | the operation and callback(b, BIO_CB_GETS|BIO_CB_RETURN, out, outl, 0L, retvalue) |
| 216 | after. |
| 217 | .IP "\fBBIO_puts(b, in)\fR" 4 |
| 218 | .IX Item "BIO_puts(b, in)" |
| 219 | callback(b, \s-1BIO_CB_WRITE\s0, in, 0, 0L, 1L) is called before |
| 220 | the operation and callback(b, BIO_CB_WRITE|BIO_CB_RETURN, in, 0, 0L, retvalue) |
| 221 | after. |
| 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)" |
| 224 | callback(b,BIO_CB_CTRL,parg,cmd,larg,1L) is called before the call and |
| 225 | callback(b,BIO_CB_CTRL|BIO_CB_RETURN,parg,cmd, larg,ret) after. |
| 226 | .SH "EXAMPLE" |
| 227 | .IX Header "EXAMPLE" |
| 228 | The \fIBIO_debug_callback()\fR function is a good example, its source is |
| 229 | in crypto/bio/bio_cb.c |
| 230 | .SH "SEE ALSO" |
| 231 | .IX Header "SEE ALSO" |
| 232 | \&\s-1TBA\s0 |