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d572cb6c DSH |
1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
b055fceb | 5 | BIO_set_callback_ex, BIO_get_callback_ex, BIO_set_callback, BIO_get_callback, |
121677b4 RS |
6 | BIO_set_callback_arg, BIO_get_callback_arg, BIO_debug_callback, |
7 | BIO_callback_fn_ex, BIO_callback_fn | |
b055fceb | 8 | - BIO callback functions |
d572cb6c DSH |
9 | |
10 | =head1 SYNOPSIS | |
11 | ||
12 | #include <openssl/bio.h> | |
13 | ||
b055fceb MC |
14 | typedef long (*BIO_callback_fn_ex)(BIO *b, int oper, const char *argp, |
15 | size_t len, int argi, | |
16 | long argl, int ret, size_t *processed); | |
91da5e77 RS |
17 | typedef long (*BIO_callback_fn)(BIO *b, int oper, const char *argp, int argi, |
18 | long argl, long ret); | |
d572cb6c | 19 | |
b055fceb MC |
20 | void BIO_set_callback_ex(BIO *b, BIO_callback_fn_ex callback); |
21 | BIO_callback_fn_ex BIO_get_callback_ex(const BIO *b); | |
22 | ||
91da5e77 RS |
23 | void BIO_set_callback(BIO *b, BIO_callack_fn cb); |
24 | BIO_callack_fn BIO_get_callback(BIO *b); | |
25 | void BIO_set_callback_arg(BIO *b, char *arg); | |
26 | char *BIO_get_callback_arg(const BIO *b); | |
27 | ||
28 | long BIO_debug_callback(BIO *bio, int cmd, const char *argp, int argi, | |
29 | long argl, long ret); | |
d572cb6c DSH |
30 | |
31 | =head1 DESCRIPTION | |
32 | ||
b055fceb MC |
33 | BIO_set_callback_ex() and BIO_get_callback_ex() set and retrieve the BIO |
34 | callback. The callback is called during most high level BIO operations. It can | |
35 | be used for debugging purposes to trace operations on a BIO or to modify its | |
36 | operation. | |
37 | ||
38 | BIO_set_callback() and BIO_get_callback() set and retrieve the old format BIO | |
39 | callback. New code should not use these functions, but they are retained for | |
40 | backwards compatbility. Any callback set via BIO_set_callback_ex() will get | |
41 | called in preference to any set by BIO_set_callback(). | |
d572cb6c DSH |
42 | |
43 | BIO_set_callback_arg() and BIO_get_callback_arg() are macros which can be | |
44 | used to set and retrieve an argument for use in the callback. | |
45 | ||
46 | BIO_debug_callback() is a standard debugging callback which prints | |
47 | out information relating to each BIO operation. If the callback | |
91da5e77 | 48 | argument is set it is interpreted as a BIO to send the information |
d572cb6c DSH |
49 | to, otherwise stderr is used. |
50 | ||
b055fceb MC |
51 | BIO_callback_fn_ex() is the type of the callback function and BIO_callback_fn() |
52 | is the type of the old format callback function. The meaning of each argument | |
53 | is described below: | |
d572cb6c | 54 | |
91da5e77 | 55 | =over |
2a5f907e CS |
56 | |
57 | =item B<b> | |
58 | ||
d572cb6c DSH |
59 | The BIO the callback is attached to is passed in B<b>. |
60 | ||
2a5f907e CS |
61 | =item B<oper> |
62 | ||
d572cb6c DSH |
63 | B<oper> is set to the operation being performed. For some operations |
64 | the callback is called twice, once before and once after the actual | |
65 | operation, the latter case has B<oper> or'ed with BIO_CB_RETURN. | |
66 | ||
b055fceb MC |
67 | =item B<len> |
68 | ||
69 | The length of the data requested to be read or written. This is only useful if | |
70 | B<oper> is BIO_CB_READ, BIO_CB_WRITE or BIO_CB_GETS. | |
71 | ||
2a5f907e CS |
72 | =item B<argp> B<argi> B<argl> |
73 | ||
d572cb6c DSH |
74 | The meaning of the arguments B<argp>, B<argi> and B<argl> depends on |
75 | the value of B<oper>, that is the operation being performed. | |
76 | ||
b055fceb MC |
77 | =item B<processed> |
78 | ||
79 | B<processed> is a pointer to a location which will be updated with the amount of | |
4e3973b4 | 80 | data that was actually read or written. Only used for BIO_CB_READ, BIO_CB_WRITE, |
b055fceb MC |
81 | BIO_CB_GETS and BIO_CB_PUTS. |
82 | ||
2a5f907e CS |
83 | =item B<ret> |
84 | ||
91da5e77 | 85 | B<ret> is the return value that would be returned to the |
d572cb6c DSH |
86 | application if no callback were present. The actual value returned |
87 | is the return value of the callback itself. In the case of callbacks | |
91da5e77 | 88 | called before the actual BIO operation 1 is placed in B<ret>, if |
d572cb6c DSH |
89 | the return value is not positive it will be immediately returned to |
90 | the application and the BIO operation will not be performed. | |
91 | ||
91da5e77 RS |
92 | =back |
93 | ||
94 | The callback should normally simply return B<ret> when it has | |
95 | finished processing, unless it specifically wishes to modify the | |
d572cb6c DSH |
96 | value returned to the application. |
97 | ||
98 | =head1 CALLBACK OPERATIONS | |
99 | ||
91da5e77 RS |
100 | In the notes below, B<callback> defers to the actual callback |
101 | function that is called. | |
102 | ||
d572cb6c DSH |
103 | =over 4 |
104 | ||
105 | =item B<BIO_free(b)> | |
106 | ||
b055fceb MC |
107 | callback_ex(b, BIO_CB_FREE, NULL, 0, 0, 0L, 1L, NULL) |
108 | ||
109 | or | |
110 | ||
111 | callback(b, BIO_CB_FREE, NULL, 0L, 0L, 1L) | |
112 | ||
113 | is called before the free operation. | |
114 | ||
4e3973b4 | 115 | =item B<BIO_read_ex(b, data, dlen, readbytes)> |
d572cb6c | 116 | |
4e3973b4 | 117 | callback_ex(b, BIO_CB_READ, data, dlen, 0, 0L, 1L, readbytes) |
b055fceb MC |
118 | |
119 | or | |
120 | ||
4e3973b4 BK |
121 | callback(b, BIO_CB_READ, data, dlen, 0L, 1L) |
122 | ||
b055fceb MC |
123 | is called before the read and |
124 | ||
4e3973b4 | 125 | callback_ex(b, BIO_CB_READ | BIO_CB_RETURN, data, dlen, 0, 0L, retvalue, readbytes) |
b055fceb MC |
126 | |
127 | or | |
128 | ||
4e3973b4 | 129 | callback(b, BIO_CB_READ|BIO_CB_RETURN, data, dlen, 0L, retvalue) |
d572cb6c | 130 | |
d572cb6c DSH |
131 | after. |
132 | ||
4e3973b4 | 133 | =item B<BIO_write(b, data, dlen, written)> |
b055fceb | 134 | |
4e3973b4 | 135 | callback_ex(b, BIO_CB_WRITE, data, dlen, 0, 0L, 1L, written) |
b055fceb MC |
136 | |
137 | or | |
138 | ||
4e3973b4 | 139 | callback(b, BIO_CB_WRITE, datat, dlen, 0L, 1L) |
b055fceb MC |
140 | |
141 | is called before the write and | |
142 | ||
4e3973b4 | 143 | callback_ex(b, BIO_CB_WRITE | BIO_CB_RETURN, data, dlen, 0, 0L, retvalue, written) |
b055fceb MC |
144 | |
145 | or | |
146 | ||
4e3973b4 | 147 | callback(b, BIO_CB_WRITE|BIO_CB_RETURN, data, dlen, 0L, retvalue) |
d572cb6c | 148 | |
d572cb6c DSH |
149 | after. |
150 | ||
4e3973b4 | 151 | =item B<BIO_gets(b, buf, size)> |
d572cb6c | 152 | |
4e3973b4 | 153 | callback_ex(b, BIO_CB_GETS, buf, size, 0, 0L, 1, NULL, NULL) |
b055fceb MC |
154 | |
155 | or | |
156 | ||
4e3973b4 | 157 | callback(b, BIO_CB_GETS, buf, size, 0L, 1L) |
b055fceb MC |
158 | |
159 | is called before the operation and | |
160 | ||
4e3973b4 | 161 | callback_ex(b, BIO_CB_GETS | BIO_CB_RETURN, buf, size, 0, 0L, retvalue, readbytes) |
b055fceb MC |
162 | |
163 | or | |
164 | ||
4e3973b4 | 165 | callback(b, BIO_CB_GETS|BIO_CB_RETURN, buf, size, 0L, retvalue) |
b055fceb | 166 | |
d572cb6c DSH |
167 | after. |
168 | ||
4e3973b4 | 169 | =item B<BIO_puts(b, buf)> |
d572cb6c | 170 | |
4e3973b4 | 171 | callback_ex(b, BIO_CB_PUTS, buf, 0, 0, 0L, 1L, NULL); |
b055fceb MC |
172 | |
173 | or | |
174 | ||
4e3973b4 | 175 | callback(b, BIO_CB_PUTS, buf, 0, 0L, 1L) |
b055fceb MC |
176 | |
177 | is called before the operation and | |
178 | ||
4e3973b4 | 179 | callback_ex(b, BIO_CB_PUTS | BIO_CB_RETURN, buf, 0, 0, 0L, retvalue, written) |
b055fceb MC |
180 | |
181 | or | |
182 | ||
4e3973b4 | 183 | callback(b, BIO_CB_WRITE|BIO_CB_RETURN, buf, 0, 0L, retvalue) |
b055fceb | 184 | |
d572cb6c DSH |
185 | after. |
186 | ||
187 | =item B<BIO_ctrl(BIO *b, int cmd, long larg, void *parg)> | |
188 | ||
b055fceb MC |
189 | callback_ex(b, BIO_CB_CTRL, parg, 0, cmd, larg, 1L, NULL) |
190 | ||
191 | or | |
192 | ||
193 | callback(b, BIO_CB_CTRL, parg, cmd, larg, 1L) | |
194 | ||
195 | is called before the call and | |
196 | ||
197 | callback_ex(b, BIO_CB_CTRL | BIO_CB_RETURN, parg, 0, cmd, larg, ret, NULL) | |
198 | ||
199 | or | |
200 | ||
201 | callback(b, BIO_CB_CTRL|BIO_CB_RETURN, parg, cmd, larg, ret) | |
4e3973b4 | 202 | |
b055fceb | 203 | after. |
d572cb6c DSH |
204 | |
205 | =back | |
206 | ||
207 | =head1 EXAMPLE | |
208 | ||
209 | The BIO_debug_callback() function is a good example, its source is | |
210 | in crypto/bio/bio_cb.c | |
211 | ||
e2f92610 RS |
212 | =head1 COPYRIGHT |
213 | ||
214 | Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved. | |
215 | ||
216 | Licensed under the OpenSSL license (the "License"). You may not use | |
217 | this file except in compliance with the License. You can obtain a copy | |
218 | in the file LICENSE in the source distribution or at | |
219 | L<https://www.openssl.org/source/license.html>. | |
220 | ||
221 | =cut |