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133 .\" ========================================================================
135 .IX Title "BIO_CTRL 3"
136 .TH BIO_CTRL 3 "2020-04-21" "1.1.1g" "OpenSSL"
137 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
138 .\" way too many mistakes in technical documents.
142 BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl, BIO_reset, BIO_seek, BIO_tell, BIO_flush, BIO_eof, BIO_set_close, BIO_get_close, BIO_pending, BIO_wpending, BIO_ctrl_pending, BIO_ctrl_wpending, BIO_get_info_callback, BIO_set_info_callback, BIO_info_cb \&\- BIO control operations
144 .IX Header "SYNOPSIS"
146 \& #include <openssl/bio.h>
148 \& typedef int BIO_info_cb(BIO *b, int state, int res);
150 \& long BIO_ctrl(BIO *bp, int cmd, long larg, void *parg);
151 \& long BIO_callback_ctrl(BIO *b, int cmd, BIO_info_cb *cb);
152 \& char *BIO_ptr_ctrl(BIO *bp, int cmd, long larg);
153 \& long BIO_int_ctrl(BIO *bp, int cmd, long larg, int iarg);
155 \& int BIO_reset(BIO *b);
156 \& int BIO_seek(BIO *b, int ofs);
157 \& int BIO_tell(BIO *b);
158 \& int BIO_flush(BIO *b);
159 \& int BIO_eof(BIO *b);
160 \& int BIO_set_close(BIO *b, long flag);
161 \& int BIO_get_close(BIO *b);
162 \& int BIO_pending(BIO *b);
163 \& int BIO_wpending(BIO *b);
164 \& size_t BIO_ctrl_pending(BIO *b);
165 \& size_t BIO_ctrl_wpending(BIO *b);
167 \& int BIO_get_info_callback(BIO *b, BIO_info_cb **cbp);
168 \& int BIO_set_info_callback(BIO *b, BIO_info_cb *cb);
171 .IX Header "DESCRIPTION"
172 \&\fBBIO_ctrl()\fR, \fBBIO_callback_ctrl()\fR, \fBBIO_ptr_ctrl()\fR and \fBBIO_int_ctrl()\fR
173 are \s-1BIO\s0 \*(L"control\*(R" operations taking arguments of various types.
174 These functions are not normally called directly, various macros
175 are used instead. The standard macros are described below, macros
176 specific to a particular type of \s-1BIO\s0 are described in the specific
177 BIOs manual page as well as any special features of the standard
180 \&\fBBIO_reset()\fR typically resets a \s-1BIO\s0 to some initial state, in the case
181 of file related BIOs for example it rewinds the file pointer to the
184 \&\fBBIO_seek()\fR resets a file related \s-1BIO\s0's (that is file descriptor and
185 \&\s-1FILE\s0 BIOs) file position pointer to \fBofs\fR bytes from start of file.
187 \&\fBBIO_tell()\fR returns the current file position of a file related \s-1BIO.\s0
189 \&\fBBIO_flush()\fR normally writes out any internally buffered data, in some
190 cases it is used to signal \s-1EOF\s0 and that no more data will be written.
192 \&\fBBIO_eof()\fR returns 1 if the \s-1BIO\s0 has read \s-1EOF,\s0 the precise meaning of
193 \&\*(L"\s-1EOF\*(R"\s0 varies according to the \s-1BIO\s0 type.
195 \&\fBBIO_set_close()\fR sets the \s-1BIO\s0 \fBb\fR close flag to \fBflag\fR. \fBflag\fR can
196 take the value \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE.\s0 Typically \s-1BIO_CLOSE\s0 is used
197 in a source/sink \s-1BIO\s0 to indicate that the underlying I/O stream should
198 be closed when the \s-1BIO\s0 is freed.
200 \&\fBBIO_get_close()\fR returns the BIOs close flag.
202 \&\fBBIO_pending()\fR, \fBBIO_ctrl_pending()\fR, \fBBIO_wpending()\fR and \fBBIO_ctrl_wpending()\fR
203 return the number of pending characters in the BIOs read and write buffers.
204 Not all BIOs support these calls. \fBBIO_ctrl_pending()\fR and \fBBIO_ctrl_wpending()\fR
205 return a size_t type and are functions, \fBBIO_pending()\fR and \fBBIO_wpending()\fR are
206 macros which call \fBBIO_ctrl()\fR.
208 .IX Header "RETURN VALUES"
209 \&\fBBIO_reset()\fR normally returns 1 for success and 0 or \-1 for failure. File
210 BIOs are an exception, they return 0 for success and \-1 for failure.
212 \&\fBBIO_seek()\fR and \fBBIO_tell()\fR both return the current file position on success
213 and \-1 for failure, except file BIOs which for \fBBIO_seek()\fR always return 0
214 for success and \-1 for failure.
216 \&\fBBIO_flush()\fR returns 1 for success and 0 or \-1 for failure.
218 \&\fBBIO_eof()\fR returns 1 if \s-1EOF\s0 has been reached 0 otherwise.
220 \&\fBBIO_set_close()\fR always returns 1.
222 \&\fBBIO_get_close()\fR returns the close flag value: \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE.\s0
224 \&\fBBIO_pending()\fR, \fBBIO_ctrl_pending()\fR, \fBBIO_wpending()\fR and \fBBIO_ctrl_wpending()\fR
225 return the amount of pending data.
228 \&\fBBIO_flush()\fR, because it can write data may return 0 or \-1 indicating
229 that the call should be retried later in a similar manner to \fBBIO_write_ex()\fR.
230 The \fBBIO_should_retry()\fR call should be used and appropriate action taken
233 The return values of \fBBIO_pending()\fR and \fBBIO_wpending()\fR may not reliably
234 determine the amount of pending data in all cases. For example in the
235 case of a file \s-1BIO\s0 some data may be available in the \s-1FILE\s0 structures
236 internal buffers but it is not possible to determine this in a
237 portably way. For other types of \s-1BIO\s0 they may not be supported.
239 Filter BIOs if they do not internally handle a particular \fBBIO_ctrl()\fR
240 operation usually pass the operation to the next \s-1BIO\s0 in the chain.
241 This often means there is no need to locate the required \s-1BIO\s0 for
242 a particular operation, it can be called on a chain and it will
243 be automatically passed to the relevant \s-1BIO.\s0 However this can cause
244 unexpected results: for example no current filter BIOs implement
245 \&\fBBIO_seek()\fR, but this may still succeed if the chain ends in a \s-1FILE\s0
246 or file descriptor \s-1BIO.\s0
248 Source/sink BIOs return an 0 if they do not recognize the \fBBIO_ctrl()\fR
252 Some of the return values are ambiguous and care should be taken. In
253 particular a return value of 0 can be returned if an operation is not
254 supported, if an error occurred, if \s-1EOF\s0 has not been reached and in
255 the case of \fBBIO_seek()\fR on a file \s-1BIO\s0 for a successful operation.
257 .IX Header "COPYRIGHT"
258 Copyright 2000\-2016 The OpenSSL Project Authors. All Rights Reserved.
260 Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use
261 this file except in compliance with the License. You can obtain a copy
262 in the file \s-1LICENSE\s0 in the source distribution or at
263 <https://www.openssl.org/source/license.html>.