1BIO_CTRL(3) OpenSSL BIO_CTRL(3)
2
6 BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl, BIO_reset,
7 BIO_seek, BIO_tell, BIO_flush, BIO_eof, BIO_set_close, BIO_get_close,
8 BIO_pending, BIO_wpending, BIO_ctrl_pending, BIO_ctrl_wpending,
9 BIO_get_info_callback, BIO_set_info_callback, BIO_info_cb - BIO control
10 operations
11
13 #include <openssl/bio.h>
14 typedef int BIO_info_cb(BIO *b, int state, int res);
16 long BIO_ctrl(BIO *bp, int cmd, long larg, void *parg);
18 long BIO_callback_ctrl(BIO *b, int cmd, BIO_info_cb *cb);
19 char *BIO_ptr_ctrl(BIO *bp, int cmd, long larg);
20 long BIO_int_ctrl(BIO *bp, int cmd, long larg, int iarg);
21 int BIO_reset(BIO *b);
23 int BIO_seek(BIO *b, int ofs);
24 int BIO_tell(BIO *b);
25 int BIO_flush(BIO *b);
26 int BIO_eof(BIO *b);
27 int BIO_set_close(BIO *b, long flag);
28 int BIO_get_close(BIO *b);
29 int BIO_pending(BIO *b);
30 int BIO_wpending(BIO *b);
31 size_t BIO_ctrl_pending(BIO *b);
32 size_t BIO_ctrl_wpending(BIO *b);
33 int BIO_get_info_callback(BIO *b, BIO_info_cb **cbp);
35 int BIO_set_info_callback(BIO *b, BIO_info_cb *cb);
36
38 BIO_ctrl(), BIO_callback_ctrl(), BIO_ptr_ctrl() and BIO_int_ctrl() are
39 BIO "control" operations taking arguments of various types. These
40 functions are not normally called directly, various macros are used
41 instead. The standard macros are described below, macros specific to a
42 particular type of BIO are described in the specific BIOs manual page
43 as well as any special features of the standard calls.
44 BIO_reset() typically resets a BIO to some initial state, in the case
46 of file related BIOs for example it rewinds the file pointer to the
47 start of the file.
48 BIO_seek() resets a file related BIO's (that is file descriptor and
50 FILE BIOs) file position pointer to ofs bytes from start of file.
51 BIO_tell() returns the current file position of a file related BIO.
53 BIO_flush() normally writes out any internally buffered data, in some
55 cases it is used to signal EOF and that no more data will be written.
56 BIO_eof() returns 1 if the BIO has read EOF, the precise meaning of
58 "EOF" varies according to the BIO type.
59 BIO_set_close() sets the BIO b close flag to flag. flag can take the
61 value BIO_CLOSE or BIO_NOCLOSE. Typically BIO_CLOSE is used in a
62 source/sink BIO to indicate that the underlying I/O stream should be
63 closed when the BIO is freed.
64 BIO_get_close() returns the BIOs close flag.
66 BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and
68 BIO_ctrl_wpending() return the number of pending characters in the BIOs
69 read and write buffers. Not all BIOs support these calls.
70 BIO_ctrl_pending() and BIO_ctrl_wpending() return a size_t type and are
71 functions, BIO_pending() and BIO_wpending() are macros which call
72 BIO_ctrl().
73
75 BIO_reset() normally returns 1 for success and 0 or -1 for failure.
76 File BIOs are an exception, they return 0 for success and -1 for
77 failure.
78 BIO_seek() and BIO_tell() both return the current file position on
80 success and -1 for failure, except file BIOs which for BIO_seek()
81 always return 0 for success and -1 for failure.
82 BIO_flush() returns 1 for success and 0 or -1 for failure.
84 BIO_eof() returns 1 if EOF has been reached 0 otherwise.
86 BIO_set_close() always returns 1.
88 BIO_get_close() returns the close flag value: BIO_CLOSE or BIO_NOCLOSE.
90 BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and
92 BIO_ctrl_wpending() return the amount of pending data.
93
95 BIO_flush(), because it can write data may return 0 or -1 indicating
96 that the call should be retried later in a similar manner to
97 BIO_write_ex(). The BIO_should_retry() call should be used and
98 appropriate action taken is the call fails.
99 The return values of BIO_pending() and BIO_wpending() may not reliably
101 determine the amount of pending data in all cases. For example in the
102 case of a file BIO some data may be available in the FILE structures
103 internal buffers but it is not possible to determine this in a portably
104 way. For other types of BIO they may not be supported.
105 Filter BIOs if they do not internally handle a particular BIO_ctrl()
107 operation usually pass the operation to the next BIO in the chain.
108 This often means there is no need to locate the required BIO for a
109 particular operation, it can be called on a chain and it will be
110 automatically passed to the relevant BIO. However, this can cause
111 unexpected results: for example no current filter BIOs implement
112 BIO_seek(), but this may still succeed if the chain ends in a FILE or
113 file descriptor BIO.
114 Source/sink BIOs return an 0 if they do not recognize the BIO_ctrl()
116 operation.
117
119 Some of the return values are ambiguous and care should be taken. In
120 particular a return value of 0 can be returned if an operation is not
121 supported, if an error occurred, if EOF has not been reached and in the
122 case of BIO_seek() on a file BIO for a successful operation.
123
125 Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
126 Licensed under the OpenSSL license (the "License"). You may not use
128 this file except in compliance with the License. You can obtain a copy
129 in the file LICENSE in the source distribution or at
130 <https://www.openssl.org/source/license.html>.
1311.1.1k 2021-03-26 BIO_CTRL(3)