zte's code,first commit
Change-Id: I9a04da59e459a9bc0d67f101f700d9d7dc8d681b
diff --git a/ap/lib/libssl/openssl-1.1.1o/doc/man3/BIO_push.pod b/ap/lib/libssl/openssl-1.1.1o/doc/man3/BIO_push.pod
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+=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 *next);
+ BIO *BIO_pop(BIO *b);
+ void BIO_set_next(BIO *b, BIO *next);
+
+=head1 DESCRIPTION
+
+BIO_push() pushes I<b> on I<next>.
+If I<b> is NULL the function does nothing and returns I<next>.
+Otherwise it prepends I<b>, which may be a single BIO or a chain of BIOs,
+to I<next> (unless I<next> is NULL).
+It then makes a control call on I<b> and returns I<b>.
+
+BIO_pop() removes the BIO I<b> from any chain is is part of.
+If I<b> is NULL the function does nothing and returns NULL.
+Otherwise it makes a control call on I<b> and
+returns the next BIO in the chain, or NULL if there is no next BIO.
+The removed BIO becomes a single BIO with no association with
+the original chain, it can thus be freed or be made part of a different chain.
+
+BIO_set_next() replaces the existing next BIO in a chain with the BIO pointed to
+by I<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 RETURN VALUES
+
+BIO_push() returns the head of the chain,
+which usually is I<b>, or I<next> if I<b> is NULL.
+
+BIO_pop() returns the next BIO in the chain,
+or NULL if there is no next BIO.
+
+=head1 EXAMPLES
+
+For these examples suppose I<md1> and I<md2> are digest BIOs,
+I<b64> is a base64 BIO and I<f> is a file BIO.
+
+If the call:
+
+ BIO_push(b64, f);
+
+is made then the new chain will be I<b64-f>. After making the calls
+
+ BIO_push(md2, b64);
+ BIO_push(md1, md2);
+
+the new chain is I<md1-md2-b64-f>. Data written to I<md1> will be digested
+by I<md1> and I<md2>, base64 encoded, and finally written to I<f>.
+
+It should be noted that reading causes data to pass in the reverse
+direction, that is data is read from I<f>, base64 decoded,
+and digested by I<md2> and then I<md1>.
+
+The call:
+
+ BIO_pop(md2);
+
+will return I<b64> and the new chain will be I<md1-b64-f>.
+Data can be written to and read from I<md1> as before,
+except that I<md2> will no more be applied.
+
+=head1 SEE ALSO
+
+L<bio>
+
+=head1 HISTORY
+
+The BIO_set_next() function was added in OpenSSL 1.1.0.
+
+=head1 COPYRIGHT
+
+Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
+
+Licensed under the OpenSSL license (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