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131 .IX Title "BIO_ctrl 3"
132 .TH BIO_ctrl 3 "2017-05-25" "1.0.2l" "OpenSSL"
133 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
134 .\" way too many mistakes in technical documents.
138 BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl, BIO_reset,
139 BIO_seek, BIO_tell, BIO_flush, BIO_eof, BIO_set_close, BIO_get_close,
140 BIO_pending, BIO_wpending, BIO_ctrl_pending, BIO_ctrl_wpending,
141 BIO_get_info_callback, BIO_set_info_callback \- BIO control operations
143 .IX Header "SYNOPSIS"
145 \& #include <openssl/bio.h>
147 \& long BIO_ctrl(BIO *bp,int cmd,long larg,void *parg);
148 \& long BIO_callback_ctrl(BIO *b, int cmd, void (*fp)(struct bio_st *, int, const char *, int, long, long));
149 \& char * BIO_ptr_ctrl(BIO *bp,int cmd,long larg);
150 \& long BIO_int_ctrl(BIO *bp,int cmd,long larg,int iarg);
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);
164 \& int BIO_get_info_callback(BIO *b,bio_info_cb **cbp);
165 \& int BIO_set_info_callback(BIO *b,bio_info_cb *cb);
167 \& typedef void bio_info_cb(BIO *b, int oper, const char *ptr, int arg1, long arg2, long arg3);
170 .IX Header "DESCRIPTION"
171 \&\fIBIO_ctrl()\fR, \fIBIO_callback_ctrl()\fR, \fIBIO_ptr_ctrl()\fR and \fIBIO_int_ctrl()\fR
172 are \s-1BIO \s0\*(L"control\*(R" operations taking arguments of various types.
173 These functions are not normally called directly, various macros
174 are used instead. The standard macros are described below, macros
175 specific to a particular type of \s-1BIO\s0 are described in the specific
176 BIOs manual page as well as any special features of the standard
179 \&\fIBIO_reset()\fR typically resets a \s-1BIO\s0 to some initial state, in the case
180 of file related BIOs for example it rewinds the file pointer to the
183 \&\fIBIO_seek()\fR resets a file related \s-1BIO\s0's (that is file descriptor and
184 \&\s-1FILE\s0 BIOs) file position pointer to \fBofs\fR bytes from start of file.
186 \&\fIBIO_tell()\fR returns the current file position of a file related \s-1BIO.\s0
188 \&\fIBIO_flush()\fR normally writes out any internally buffered data, in some
189 cases it is used to signal \s-1EOF\s0 and that no more data will be written.
191 \&\fIBIO_eof()\fR returns 1 if the \s-1BIO\s0 has read \s-1EOF,\s0 the precise meaning of
192 \&\*(L"\s-1EOF\*(R"\s0 varies according to the \s-1BIO\s0 type.
194 \&\fIBIO_set_close()\fR sets the \s-1BIO \s0\fBb\fR close flag to \fBflag\fR. \fBflag\fR can
195 take the value \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE.\s0 Typically \s-1BIO_CLOSE\s0 is used
196 in a source/sink \s-1BIO\s0 to indicate that the underlying I/O stream should
197 be closed when the \s-1BIO\s0 is freed.
199 \&\fIBIO_get_close()\fR returns the BIOs close flag.
201 \&\fIBIO_pending()\fR, \fIBIO_ctrl_pending()\fR, \fIBIO_wpending()\fR and \fIBIO_ctrl_wpending()\fR
202 return the number of pending characters in the BIOs read and write buffers.
203 Not all BIOs support these calls. \fIBIO_ctrl_pending()\fR and \fIBIO_ctrl_wpending()\fR
204 return a size_t type and are functions, \fIBIO_pending()\fR and \fIBIO_wpending()\fR are
205 macros which call \fIBIO_ctrl()\fR.
207 .IX Header "RETURN VALUES"
208 \&\fIBIO_reset()\fR normally returns 1 for success and 0 or \-1 for failure. File
209 BIOs are an exception, they return 0 for success and \-1 for failure.
211 \&\fIBIO_seek()\fR and \fIBIO_tell()\fR both return the current file position on success
212 and \-1 for failure, except file BIOs which for \fIBIO_seek()\fR always return 0
213 for success and \-1 for failure.
215 \&\fIBIO_flush()\fR returns 1 for success and 0 or \-1 for failure.
217 \&\fIBIO_eof()\fR returns 1 if \s-1EOF\s0 has been reached 0 otherwise.
219 \&\fIBIO_set_close()\fR always returns 1.
221 \&\fIBIO_get_close()\fR returns the close flag value: \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE.\s0
223 \&\fIBIO_pending()\fR, \fIBIO_ctrl_pending()\fR, \fIBIO_wpending()\fR and \fIBIO_ctrl_wpending()\fR
224 return the amount of pending data.
227 \&\fIBIO_flush()\fR, because it can write data may return 0 or \-1 indicating
228 that the call should be retried later in a similar manner to \fIBIO_write()\fR.
229 The \fIBIO_should_retry()\fR call should be used and appropriate action taken
232 The return values of \fIBIO_pending()\fR and \fIBIO_wpending()\fR may not reliably
233 determine the amount of pending data in all cases. For example in the
234 case of a file \s-1BIO\s0 some data may be available in the \s-1FILE\s0 structures
235 internal buffers but it is not possible to determine this in a
236 portably way. For other types of \s-1BIO\s0 they may not be supported.
238 Filter BIOs if they do not internally handle a particular \fIBIO_ctrl()\fR
239 operation usually pass the operation to the next \s-1BIO\s0 in the chain.
240 This often means there is no need to locate the required \s-1BIO\s0 for
241 a particular operation, it can be called on a chain and it will
242 be automatically passed to the relevant \s-1BIO.\s0 However this can cause
243 unexpected results: for example no current filter BIOs implement
244 \&\fIBIO_seek()\fR, but this may still succeed if the chain ends in a \s-1FILE\s0
245 or file descriptor \s-1BIO.\s0
247 Source/sink BIOs return an 0 if they do not recognize the \fIBIO_ctrl()\fR
251 Some of the return values are ambiguous and care should be taken. In
252 particular a return value of 0 can be returned if an operation is not
253 supported, if an error occurred, if \s-1EOF\s0 has not been reached and in
254 the case of \fIBIO_seek()\fR on a file \s-1BIO\s0 for a successful operation.
256 .IX Header "SEE ALSO"