5 BIO_push, BIO_pop, BIO_set_next - add and remove BIOs from a chain
9 #include <openssl/bio.h>
11 BIO *BIO_push(BIO *b, BIO *append);
13 void BIO_set_next(BIO *b, BIO *next);
17 The BIO_push() function appends the BIO B<append> to B<b>, it returns
20 BIO_pop() removes the BIO B<b> from a chain and returns the next BIO
21 in the chain, or NULL if there is no next BIO. The removed BIO then
22 becomes a single BIO with no association with the original chain,
23 it can thus be freed or attached to a different chain.
25 BIO_set_next() replaces the existing next BIO in a chain with the BIO pointed to
26 by B<next>. The new chain may include some of the same BIOs from the old chain
27 or it may be completely different.
31 The names of these functions are perhaps a little misleading. BIO_push()
32 joins two BIO chains whereas BIO_pop() deletes a single BIO from a chain,
33 the deleted BIO does not need to be at the end of a chain.
35 The process of calling BIO_push() and BIO_pop() on a BIO may have additional
36 consequences (a control call is made to the affected BIOs) any effects will
37 be noted in the descriptions of individual BIOs.
41 For these examples suppose B<md1> and B<md2> are digest BIOs, B<b64> is
42 a base64 BIO and B<f> is a file BIO.
48 is made then the new chain will be B<b64-f>. After making the calls
53 the new chain is B<md1-md2-b64-f>. Data written to B<md1> will be digested
54 by B<md1> and B<md2>, B<base64> encoded and written to B<f>.
56 It should be noted that reading causes data to pass in the reverse
57 direction, that is data is read from B<f>, base64 B<decoded> and digested
58 by B<md1> and B<md2>. If the call:
62 The call will return B<b64> and the new chain will be B<md1-b64-f> data can
63 be written to B<md1> as before.
67 BIO_push() returns the end of the chain, B<b>.
69 BIO_pop() returns the next BIO in the chain, or NULL if there is no next
78 The BIO_set_next() function was added in OpenSSL 1.1.0.
82 Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
84 Licensed under the Apache License 2.0 (the "License"). You may not use
85 this file except in compliance with the License. You can obtain a copy
86 in the file LICENSE in the source distribution or at
87 L<https://www.openssl.org/source/license.html>.