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135 .\" ========================================================================
136 .\"
137 .IX Title "BIO_ctrl 3"
138 .TH BIO_ctrl 3 "2009-07-19" "1.0.1n" "OpenSSL"
139 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
140 .\" way too many mistakes in technical documents.
141 .if n .ad l
142 .nh
143 .SH "NAME"
144 BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl, BIO_reset,
145 BIO_seek, BIO_tell, BIO_flush, BIO_eof, BIO_set_close, BIO_get_close,
146 BIO_pending, BIO_wpending, BIO_ctrl_pending, BIO_ctrl_wpending,
147 BIO_get_info_callback, BIO_set_info_callback \- BIO control operations
148 .SH "LIBRARY"
149 libcrypto, -lcrypto
150 .SH "SYNOPSIS"
151 .IX Header "SYNOPSIS"
152 .Vb 1
153 \& #include <openssl/bio.h>
154 \&
155 \& long BIO_ctrl(BIO *bp,int cmd,long larg,void *parg);
156 \& long BIO_callback_ctrl(BIO *b, int cmd, void (*fp)(struct bio_st *, int, const char *, int, long, long));
157 \& char * BIO_ptr_ctrl(BIO *bp,int cmd,long larg);
158 \& long BIO_int_ctrl(BIO *bp,int cmd,long larg,int iarg);
159 \&
160 \& int BIO_reset(BIO *b);
161 \& int BIO_seek(BIO *b, int ofs);
162 \& int BIO_tell(BIO *b);
163 \& int BIO_flush(BIO *b);
164 \& int BIO_eof(BIO *b);
165 \& int BIO_set_close(BIO *b,long flag);
166 \& int BIO_get_close(BIO *b);
167 \& int BIO_pending(BIO *b);
168 \& int BIO_wpending(BIO *b);
169 \& size_t BIO_ctrl_pending(BIO *b);
170 \& size_t BIO_ctrl_wpending(BIO *b);
171 \&
172 \& int BIO_get_info_callback(BIO *b,bio_info_cb **cbp);
173 \& int BIO_set_info_callback(BIO *b,bio_info_cb *cb);
174 \&
175 \& typedef void bio_info_cb(BIO *b, int oper, const char *ptr, int arg1, long arg2, long arg3);
176 .Ve
177 .SH "DESCRIPTION"
178 .IX Header "DESCRIPTION"
179 \&\fIBIO_ctrl()\fR, \fIBIO_callback_ctrl()\fR, \fIBIO_ptr_ctrl()\fR and \fIBIO_int_ctrl()\fR
180 are \s-1BIO \s0\*(L"control\*(R" operations taking arguments of various types.
181 These functions are not normally called directly, various macros
182 are used instead. The standard macros are described below, macros
183 specific to a particular type of \s-1BIO\s0 are described in the specific
184 BIOs manual page as well as any special features of the standard
185 calls.
186 .PP
187 \&\fIBIO_reset()\fR typically resets a \s-1BIO\s0 to some initial state, in the case
188 of file related BIOs for example it rewinds the file pointer to the
189 start of the file.
190 .PP
191 \&\fIBIO_seek()\fR resets a file related \s-1BIO\s0's (that is file descriptor and
192 \&\s-1FILE\s0 BIOs) file position pointer to \fBofs\fR bytes from start of file.
193 .PP
194 \&\fIBIO_tell()\fR returns the current file position of a file related \s-1BIO.\s0
195 .PP
196 \&\fIBIO_flush()\fR normally writes out any internally buffered data, in some
197 cases it is used to signal \s-1EOF\s0 and that no more data will be written.
198 .PP
199 \&\fIBIO_eof()\fR returns 1 if the \s-1BIO\s0 has read \s-1EOF,\s0 the precise meaning of
200 \&\*(L"\s-1EOF\*(R"\s0 varies according to the \s-1BIO\s0 type.
201 .PP
202 \&\fIBIO_set_close()\fR sets the \s-1BIO \s0\fBb\fR close flag to \fBflag\fR. \fBflag\fR can
203 take the value \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE.\s0 Typically \s-1BIO_CLOSE\s0 is used
204 in a source/sink \s-1BIO\s0 to indicate that the underlying I/O stream should
205 be closed when the \s-1BIO\s0 is freed.
206 .PP
207 \&\fIBIO_get_close()\fR returns the BIOs close flag.
208 .PP
209 \&\fIBIO_pending()\fR, \fIBIO_ctrl_pending()\fR, \fIBIO_wpending()\fR and \fIBIO_ctrl_wpending()\fR
210 return the number of pending characters in the BIOs read and write buffers.
211 Not all BIOs support these calls. \fIBIO_ctrl_pending()\fR and \fIBIO_ctrl_wpending()\fR
212 return a size_t type and are functions, \fIBIO_pending()\fR and \fIBIO_wpending()\fR are
213 macros which call \fIBIO_ctrl()\fR.
214 .SH "RETURN VALUES"
215 .IX Header "RETURN VALUES"
216 \&\fIBIO_reset()\fR normally returns 1 for success and 0 or \-1 for failure. File
217 BIOs are an exception, they return 0 for success and \-1 for failure.
218 .PP
219 \&\fIBIO_seek()\fR and \fIBIO_tell()\fR both return the current file position on success
220 and \-1 for failure, except file BIOs which for \fIBIO_seek()\fR always return 0
221 for success and \-1 for failure.
222 .PP
223 \&\fIBIO_flush()\fR returns 1 for success and 0 or \-1 for failure.
224 .PP
225 \&\fIBIO_eof()\fR returns 1 if \s-1EOF\s0 has been reached 0 otherwise.
226 .PP
227 \&\fIBIO_set_close()\fR always returns 1.
228 .PP
229 \&\fIBIO_get_close()\fR returns the close flag value: \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE.\s0
230 .PP
231 \&\fIBIO_pending()\fR, \fIBIO_ctrl_pending()\fR, \fIBIO_wpending()\fR and \fIBIO_ctrl_wpending()\fR
232 return the amount of pending data.
233 .SH "NOTES"
234 .IX Header "NOTES"
235 \&\fIBIO_flush()\fR, because it can write data may return 0 or \-1 indicating
236 that the call should be retried later in a similar manner to \fIBIO_write()\fR.
237 The \fIBIO_should_retry()\fR call should be used and appropriate action taken
238 is the call fails.
239 .PP
240 The return values of \fIBIO_pending()\fR and \fIBIO_wpending()\fR may not reliably
241 determine the amount of pending data in all cases. For example in the
242 case of a file \s-1BIO\s0 some data may be available in the \s-1FILE\s0 structures
243 internal buffers but it is not possible to determine this in a
244 portably way. For other types of \s-1BIO\s0 they may not be supported.
245 .PP
246 Filter BIOs if they do not internally handle a particular \fIBIO_ctrl()\fR
247 operation usually pass the operation to the next \s-1BIO\s0 in the chain.
248 This often means there is no need to locate the required \s-1BIO\s0 for
249 a particular operation, it can be called on a chain and it will
250 be automatically passed to the relevant \s-1BIO.\s0 However this can cause
251 unexpected results: for example no current filter BIOs implement
252 \&\fIBIO_seek()\fR, but this may still succeed if the chain ends in a \s-1FILE\s0
253 or file descriptor \s-1BIO.\s0
254 .PP
255 Source/sink BIOs return an 0 if they do not recognize the \fIBIO_ctrl()\fR
256 operation.
257 .SH "BUGS"
258 .IX Header "BUGS"
259 Some of the return values are ambiguous and care should be taken. In
260 particular a return value of 0 can be returned if an operation is not
261 supported, if an error occurred, if \s-1EOF\s0 has not been reached and in
262 the case of \fIBIO_seek()\fR on a file \s-1BIO\s0 for a successful operation.
263 .SH "SEE ALSO"
264 .IX Header "SEE ALSO"
265 \&\s-1TBA\s0