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131 .IX Title "BIO_ctrl 3"
132 .TH BIO_ctrl 3 "2009-07-23" "0.9.8k" "OpenSSL"
133 .SH "NAME"
134 BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl, BIO_reset,
135 BIO_seek, BIO_tell, BIO_flush, BIO_eof, BIO_set_close, BIO_get_close,
136 BIO_pending, BIO_wpending, BIO_ctrl_pending, BIO_ctrl_wpending,
137 BIO_get_info_callback, BIO_set_info_callback \- BIO control operations
138 .SH "SYNOPSIS"
139 .IX Header "SYNOPSIS"
140 .Vb 1
141 \& #include <openssl/bio.h>
142 .Ve
143 .PP
144 .Vb 4
145 \& long BIO_ctrl(BIO *bp,int cmd,long larg,void *parg);
146 \& long BIO_callback_ctrl(BIO *b, int cmd, void (*fp)(struct bio_st *, int, const char *, int, long, long));
147 \& char * BIO_ptr_ctrl(BIO *bp,int cmd,long larg);
148 \& long BIO_int_ctrl(BIO *bp,int cmd,long larg,int iarg);
149 .Ve
150 .PP
151 .Vb 11
152 \& int BIO_reset(BIO *b);
153 \& int BIO_seek(BIO *b, int ofs);
154 \& int BIO_tell(BIO *b);
155 \& int BIO_flush(BIO *b);
156 \& int BIO_eof(BIO *b);
157 \& int BIO_set_close(BIO *b,long flag);
158 \& int BIO_get_close(BIO *b);
159 \& int BIO_pending(BIO *b);
160 \& int BIO_wpending(BIO *b);
161 \& size_t BIO_ctrl_pending(BIO *b);
162 \& size_t BIO_ctrl_wpending(BIO *b);
163 .Ve
164 .PP
165 .Vb 2
166 \& int BIO_get_info_callback(BIO *b,bio_info_cb **cbp);
167 \& int BIO_set_info_callback(BIO *b,bio_info_cb *cb);
168 .Ve
169 .PP
170 .Vb 1
171 \& typedef void bio_info_cb(BIO *b, int oper, const char *ptr, int arg1, long arg2, long arg3);
172 .Ve
173 .SH "DESCRIPTION"
174 .IX Header "DESCRIPTION"
175 \&\fIBIO_ctrl()\fR, \fIBIO_callback_ctrl()\fR, \fIBIO_ptr_ctrl()\fR and \fIBIO_int_ctrl()\fR
176 are \s-1BIO\s0 \*(L"control\*(R" operations taking arguments of various types.
177 These functions are not normally called directly, various macros
178 are used instead. The standard macros are described below, macros
179 specific to a particular type of \s-1BIO\s0 are described in the specific
180 BIOs manual page as well as any special features of the standard
181 calls.
182 .PP
183 \&\fIBIO_reset()\fR typically resets a \s-1BIO\s0 to some initial state, in the case
184 of file related BIOs for example it rewinds the file pointer to the
185 start of the file.
186 .PP
187 \&\fIBIO_seek()\fR resets a file related \s-1BIO\s0's (that is file descriptor and
188 \&\s-1FILE\s0 BIOs) file position pointer to \fBofs\fR bytes from start of file.
189 .PP
190 \&\fIBIO_tell()\fR returns the current file position of a file related \s-1BIO\s0.
191 .PP
192 \&\fIBIO_flush()\fR normally writes out any internally buffered data, in some
193 cases it is used to signal \s-1EOF\s0 and that no more data will be written.
194 .PP
195 \&\fIBIO_eof()\fR returns 1 if the \s-1BIO\s0 has read \s-1EOF\s0, the precise meaning of
196 \&\*(L"\s-1EOF\s0\*(R" varies according to the \s-1BIO\s0 type.
197 .PP
198 \&\fIBIO_set_close()\fR sets the \s-1BIO\s0 \fBb\fR close flag to \fBflag\fR. \fBflag\fR can
199 take the value \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE\s0. Typically \s-1BIO_CLOSE\s0 is used
200 in a source/sink \s-1BIO\s0 to indicate that the underlying I/O stream should
201 be closed when the \s-1BIO\s0 is freed.
202 .PP
203 \&\fIBIO_get_close()\fR returns the BIOs close flag.
204 .PP
205 \&\fIBIO_pending()\fR, \fIBIO_ctrl_pending()\fR, \fIBIO_wpending()\fR and \fIBIO_ctrl_wpending()\fR
206 return the number of pending characters in the BIOs read and write buffers.
207 Not all BIOs support these calls. \fIBIO_ctrl_pending()\fR and \fIBIO_ctrl_wpending()\fR
208 return a size_t type and are functions, \fIBIO_pending()\fR and \fIBIO_wpending()\fR are
209 macros which call \fIBIO_ctrl()\fR.
210 .SH "RETURN VALUES"
211 .IX Header "RETURN VALUES"
212 \&\fIBIO_reset()\fR normally returns 1 for success and 0 or \-1 for failure. File
213 BIOs are an exception, they return 0 for success and \-1 for failure.
214 .PP
215 \&\fIBIO_seek()\fR and \fIBIO_tell()\fR both return the current file position on success
216 and \-1 for failure, except file BIOs which for \fIBIO_seek()\fR always return 0
217 for success and \-1 for failure.
218 .PP
219 \&\fIBIO_flush()\fR returns 1 for success and 0 or \-1 for failure.
220 .PP
221 \&\fIBIO_eof()\fR returns 1 if \s-1EOF\s0 has been reached 0 otherwise.
222 .PP
223 \&\fIBIO_set_close()\fR always returns 1.
224 .PP
225 \&\fIBIO_get_close()\fR returns the close flag value: \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE\s0.
226 .PP
227 \&\fIBIO_pending()\fR, \fIBIO_ctrl_pending()\fR, \fIBIO_wpending()\fR and \fIBIO_ctrl_wpending()\fR
228 return the amount of pending data.
229 .SH "NOTES"
230 .IX Header "NOTES"
231 \&\fIBIO_flush()\fR, because it can write data may return 0 or \-1 indicating
232 that the call should be retried later in a similar manner to \fIBIO_write()\fR.
233 The \fIBIO_should_retry()\fR call should be used and appropriate action taken
234 is the call fails.
235 .PP
236 The return values of \fIBIO_pending()\fR and \fIBIO_wpending()\fR may not reliably
237 determine the amount of pending data in all cases. For example in the
238 case of a file \s-1BIO\s0 some data may be available in the \s-1FILE\s0 structures
239 internal buffers but it is not possible to determine this in a
240 portably way. For other types of \s-1BIO\s0 they may not be supported.
241 .PP
242 Filter BIOs if they do not internally handle a particular \fIBIO_ctrl()\fR
243 operation usually pass the operation to the next \s-1BIO\s0 in the chain.
244 This often means there is no need to locate the required \s-1BIO\s0 for
245 a particular operation, it can be called on a chain and it will
246 be automatically passed to the relevant \s-1BIO\s0. However this can cause
247 unexpected results: for example no current filter BIOs implement
248 \&\fIBIO_seek()\fR, but this may still succeed if the chain ends in a \s-1FILE\s0
249 or file descriptor \s-1BIO\s0.
250 .PP
251 Source/sink BIOs return an 0 if they do not recognize the \fIBIO_ctrl()\fR
252 operation.
253 .SH "BUGS"
254 .IX Header "BUGS"
255 Some of the return values are ambiguous and care should be taken. In
256 particular a return value of 0 can be returned if an operation is not
257 supported, if an error occurred, if \s-1EOF\s0 has not been reached and in
258 the case of \fIBIO_seek()\fR on a file \s-1BIO\s0 for a successful operation.
259 .SH "SEE ALSO"
260 .IX Header "SEE ALSO"
261 \&\s-1TBA\s0