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131 .IX Title "BIO_CTRL 3"
132 .TH BIO_CTRL 3 "2018-11-20" "1.1.1a" "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, 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
140 .IX Header "SYNOPSIS"
142 \& #include <openssl/bio.h>
144 \& typedef int BIO_info_cb(BIO *b, int state, int res);
146 \& long BIO_ctrl(BIO *bp, int cmd, long larg, void *parg);
147 \& long BIO_callback_ctrl(BIO *b, int cmd, BIO_info_cb *cb);
148 \& char *BIO_ptr_ctrl(BIO *bp, int cmd, long larg);
149 \& long BIO_int_ctrl(BIO *bp, int cmd, long larg, int iarg);
151 \& int BIO_reset(BIO *b);
152 \& int BIO_seek(BIO *b, int ofs);
153 \& int BIO_tell(BIO *b);
154 \& int BIO_flush(BIO *b);
155 \& int BIO_eof(BIO *b);
156 \& int BIO_set_close(BIO *b, long flag);
157 \& int BIO_get_close(BIO *b);
158 \& int BIO_pending(BIO *b);
159 \& int BIO_wpending(BIO *b);
160 \& size_t BIO_ctrl_pending(BIO *b);
161 \& size_t BIO_ctrl_wpending(BIO *b);
163 \& int BIO_get_info_callback(BIO *b, BIO_info_cb **cbp);
164 \& int BIO_set_info_callback(BIO *b, BIO_info_cb *cb);
167 .IX Header "DESCRIPTION"
168 \&\fIBIO_ctrl()\fR, \fIBIO_callback_ctrl()\fR, \fIBIO_ptr_ctrl()\fR and \fIBIO_int_ctrl()\fR
169 are \s-1BIO\s0 \*(L"control\*(R" operations taking arguments of various types.
170 These functions are not normally called directly, various macros
171 are used instead. The standard macros are described below, macros
172 specific to a particular type of \s-1BIO\s0 are described in the specific
173 BIOs manual page as well as any special features of the standard
176 \&\fIBIO_reset()\fR typically resets a \s-1BIO\s0 to some initial state, in the case
177 of file related BIOs for example it rewinds the file pointer to the
180 \&\fIBIO_seek()\fR resets a file related \s-1BIO\s0's (that is file descriptor and
181 \&\s-1FILE\s0 BIOs) file position pointer to \fBofs\fR bytes from start of file.
183 \&\fIBIO_tell()\fR returns the current file position of a file related \s-1BIO.\s0
185 \&\fIBIO_flush()\fR normally writes out any internally buffered data, in some
186 cases it is used to signal \s-1EOF\s0 and that no more data will be written.
188 \&\fIBIO_eof()\fR returns 1 if the \s-1BIO\s0 has read \s-1EOF,\s0 the precise meaning of
189 \&\*(L"\s-1EOF\*(R"\s0 varies according to the \s-1BIO\s0 type.
191 \&\fIBIO_set_close()\fR sets the \s-1BIO\s0 \fBb\fR close flag to \fBflag\fR. \fBflag\fR can
192 take the value \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE.\s0 Typically \s-1BIO_CLOSE\s0 is used
193 in a source/sink \s-1BIO\s0 to indicate that the underlying I/O stream should
194 be closed when the \s-1BIO\s0 is freed.
196 \&\fIBIO_get_close()\fR returns the BIOs close flag.
198 \&\fIBIO_pending()\fR, \fIBIO_ctrl_pending()\fR, \fIBIO_wpending()\fR and \fIBIO_ctrl_wpending()\fR
199 return the number of pending characters in the BIOs read and write buffers.
200 Not all BIOs support these calls. \fIBIO_ctrl_pending()\fR and \fIBIO_ctrl_wpending()\fR
201 return a size_t type and are functions, \fIBIO_pending()\fR and \fIBIO_wpending()\fR are
202 macros which call \fIBIO_ctrl()\fR.
204 .IX Header "RETURN VALUES"
205 \&\fIBIO_reset()\fR normally returns 1 for success and 0 or \-1 for failure. File
206 BIOs are an exception, they return 0 for success and \-1 for failure.
208 \&\fIBIO_seek()\fR and \fIBIO_tell()\fR both return the current file position on success
209 and \-1 for failure, except file BIOs which for \fIBIO_seek()\fR always return 0
210 for success and \-1 for failure.
212 \&\fIBIO_flush()\fR returns 1 for success and 0 or \-1 for failure.
214 \&\fIBIO_eof()\fR returns 1 if \s-1EOF\s0 has been reached 0 otherwise.
216 \&\fIBIO_set_close()\fR always returns 1.
218 \&\fIBIO_get_close()\fR returns the close flag value: \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE.\s0
220 \&\fIBIO_pending()\fR, \fIBIO_ctrl_pending()\fR, \fIBIO_wpending()\fR and \fIBIO_ctrl_wpending()\fR
221 return the amount of pending data.
224 \&\fIBIO_flush()\fR, because it can write data may return 0 or \-1 indicating
225 that the call should be retried later in a similar manner to \fIBIO_write_ex()\fR.
226 The \fIBIO_should_retry()\fR call should be used and appropriate action taken
229 The return values of \fIBIO_pending()\fR and \fIBIO_wpending()\fR may not reliably
230 determine the amount of pending data in all cases. For example in the
231 case of a file \s-1BIO\s0 some data may be available in the \s-1FILE\s0 structures
232 internal buffers but it is not possible to determine this in a
233 portably way. For other types of \s-1BIO\s0 they may not be supported.
235 Filter BIOs if they do not internally handle a particular \fIBIO_ctrl()\fR
236 operation usually pass the operation to the next \s-1BIO\s0 in the chain.
237 This often means there is no need to locate the required \s-1BIO\s0 for
238 a particular operation, it can be called on a chain and it will
239 be automatically passed to the relevant \s-1BIO.\s0 However this can cause
240 unexpected results: for example no current filter BIOs implement
241 \&\fIBIO_seek()\fR, but this may still succeed if the chain ends in a \s-1FILE\s0
242 or file descriptor \s-1BIO.\s0
244 Source/sink BIOs return an 0 if they do not recognize the \fIBIO_ctrl()\fR
248 Some of the return values are ambiguous and care should be taken. In
249 particular a return value of 0 can be returned if an operation is not
250 supported, if an error occurred, if \s-1EOF\s0 has not been reached and in
251 the case of \fIBIO_seek()\fR on a file \s-1BIO\s0 for a successful operation.
253 .IX Header "COPYRIGHT"
254 Copyright 2000\-2016 The OpenSSL Project Authors. All Rights Reserved.
256 Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use
257 this file except in compliance with the License. You can obtain a copy
258 in the file \s-1LICENSE\s0 in the source distribution or at
259 <https://www.openssl.org/source/license.html>.