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 control operations
10
12 #include <openssl/bio.h>
13 long BIO_ctrl(BIO *bp,int cmd,long larg,void *parg);
15 long BIO_callback_ctrl(BIO *b, int cmd, void (*fp)(struct bio_st *, int, const char *, int, long, long));
16 char * BIO_ptr_ctrl(BIO *bp,int cmd,long larg);
17 long BIO_int_ctrl(BIO *bp,int cmd,long larg,int iarg);
18 int BIO_reset(BIO *b);
20 int BIO_seek(BIO *b, int ofs);
21 int BIO_tell(BIO *b);
22 int BIO_flush(BIO *b);
23 int BIO_eof(BIO *b);
24 int BIO_set_close(BIO *b,long flag);
25 int BIO_get_close(BIO *b);
26 int BIO_pending(BIO *b);
27 int BIO_wpending(BIO *b);
28 size_t BIO_ctrl_pending(BIO *b);
29 size_t BIO_ctrl_wpending(BIO *b);
30 int BIO_get_info_callback(BIO *b,bio_info_cb **cbp);
32 int BIO_set_info_callback(BIO *b,bio_info_cb *cb);
33 typedef void bio_info_cb(BIO *b, int oper, const char *ptr, int arg1, long arg2, long arg3);
35
37 BIO_ctrl(), BIO_callback_ctrl(), BIO_ptr_ctrl() and BIO_int_ctrl() are
38 BIO "control" operations taking arguments of various types. These
39 functions are not normally called directly, various macros are used
40 instead. The standard macros are described below, macros specific to a
41 particular type of BIO are described in the specific BIOs manual page
42 as well as any special features of the standard calls.
43 BIO_reset() typically resets a BIO to some initial state, in the case
45 of file related BIOs for example it rewinds the file pointer to the
46 start of the file.
47 BIO_seek() resets a file related BIO's (that is file descriptor and
49 FILE BIOs) file position pointer to ofs bytes from start of file.
50 BIO_tell() returns the current file position of a file related BIO.
52 BIO_flush() normally writes out any internally buffered data, in some
54 cases it is used to signal EOF and that no more data will be written.
55 BIO_eof() returns 1 if the BIO has read EOF, the precise meaning of
57 "EOF" varies according to the BIO type.
58 BIO_set_close() sets the BIO b close flag to flag. flag can take the
60 value BIO_CLOSE or BIO_NOCLOSE. Typically BIO_CLOSE is used in a
61 source/sink BIO to indicate that the underlying I/O stream should be
62 closed when the BIO is freed.
63 BIO_get_close() returns the BIOs close flag.
65 BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and
67 BIO_ctrl_wpending() return the number of pending characters in the BIOs
68 read and write buffers. Not all BIOs support these calls.
69 BIO_ctrl_pending() and BIO_ctrl_wpending() return a size_t type and are
70 functions, BIO_pending() and BIO_wpending() are macros which call
71 BIO_ctrl().
72
74 BIO_reset() normally returns 1 for success and 0 or -1 for failure.
75 File BIOs are an exception, they return 0 for success and -1 for
76 failure.
77 BIO_seek() and BIO_tell() both return the current file position on
79 success and -1 for failure, except file BIOs which for BIO_seek()
80 always return 0 for success and -1 for failure.
81 BIO_flush() returns 1 for success and 0 or -1 for failure.
83 BIO_eof() returns 1 if EOF has been reached 0 otherwise.
85 BIO_set_close() always returns 1.
87 BIO_get_close() returns the close flag value: BIO_CLOSE or BIO_NOCLOSE.
89 BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and
91 BIO_ctrl_wpending() return the amount of pending data.
92
94 BIO_flush(), because it can write data may return 0 or -1 indicating
95 that the call should be retried later in a similar manner to
96 BIO_write(). The BIO_should_retry() call should be used and
97 appropriate action taken is the call fails.
98 The return values of BIO_pending() and BIO_wpending() may not reliably
100 determine the amount of pending data in all cases. For example in the
101 case of a file BIO some data may be available in the FILE structures
102 internal buffers but it is not possible to determine this in a portably
103 way. For other types of BIO they may not be supported.
104 Filter BIOs if they do not internally handle a particular BIO_ctrl()
106 operation usually pass the operation to the next BIO in the chain.
107 This often means there is no need to locate the required BIO for a
108 particular operation, it can be called on a chain and it will be
109 automatically passed to the relevant BIO. However this can cause
110 unexpected results: for example no current filter BIOs implement
111 BIO_seek(), but this may still succeed if the chain ends in a FILE or
112 file descriptor BIO.
113 Source/sink BIOs return an 0 if they do not recognize the BIO_ctrl()
115 operation.
116
118 Some of the return values are ambiguous and care should be taken. In
119 particular a return value of 0 can be returned if an operation is not
120 supported, if an error occurred, if EOF has not been reached and in the
121 case of BIO_seek() on a file BIO for a successful operation.
122
124 TBA
1251.0.2o 2020-01-28 BIO_ctrl(3)