| =pod |
| |
| =head1 NAME |
| |
| BIO_push, BIO_pop, BIO_set_next - add and remove BIOs from a chain |
| |
| =head1 SYNOPSIS |
| |
| #include <openssl/bio.h> |
| |
| BIO *BIO_push(BIO *b, BIO *append); |
| BIO *BIO_pop(BIO *b); |
| void BIO_set_next(BIO *b, BIO *next); |
| |
| =head1 DESCRIPTION |
| |
| The BIO_push() function appends the BIO B<append> to B<b>, it returns |
| B<b>. |
| |
| BIO_pop() removes the BIO B<b> from a chain and returns the next BIO |
| in the chain, or NULL if there is no next BIO. The removed BIO then |
| becomes a single BIO with no association with the original chain, |
| it can thus be freed or attached to a different chain. |
| |
| BIO_set_next() replaces the existing next BIO in a chain with the BIO pointed to |
| by B<next>. The new chain may include some of the same BIOs from the old chain |
| or it may be completely different. |
| |
| =head1 NOTES |
| |
| The names of these functions are perhaps a little misleading. BIO_push() |
| joins two BIO chains whereas BIO_pop() deletes a single BIO from a chain, |
| the deleted BIO does not need to be at the end of a chain. |
| |
| The process of calling BIO_push() and BIO_pop() on a BIO may have additional |
| consequences (a control call is made to the affected BIOs) any effects will |
| be noted in the descriptions of individual BIOs. |
| |
| =head1 EXAMPLES |
| |
| For these examples suppose B<md1> and B<md2> are digest BIOs, B<b64> is |
| a base64 BIO and B<f> is a file BIO. |
| |
| If the call: |
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| BIO_push(b64, f); |
| |
| is made then the new chain will be B<b64-f>. After making the calls |
| |
| BIO_push(md2, b64); |
| BIO_push(md1, md2); |
| |
| the new chain is B<md1-md2-b64-f>. Data written to B<md1> will be digested |
| by B<md1> and B<md2>, B<base64> encoded and written to B<f>. |
| |
| It should be noted that reading causes data to pass in the reverse |
| direction, that is data is read from B<f>, base64 B<decoded> and digested |
| by B<md1> and B<md2>. If the call: |
| |
| BIO_pop(md2); |
| |
| The call will return B<b64> and the new chain will be B<md1-b64-f> data can |
| be written to B<md1> as before. |
| |
| =head1 RETURN VALUES |
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| BIO_push() returns the end of the chain, B<b>. |
| |
| BIO_pop() returns the next BIO in the chain, or NULL if there is no next |
| BIO. |
| |
| =head1 SEE ALSO |
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| L<bio> |
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| =head1 HISTORY |
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| The BIO_set_next() function was added in OpenSSL 1.1.0. |
| |
| =head1 COPYRIGHT |
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| Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved. |
| |
| Licensed under the Apache License 2.0 (the "License"). You may not use |
| this file except in compliance with the License. You can obtain a copy |
| in the file LICENSE in the source distribution or at |
| L<https://www.openssl.org/source/license.html>. |
| |
| =cut |
