=pod

=head1 NAME

BIO_find_type, BIO_next, BIO_method_type - BIO chain traversal

=head1 SYNOPSIS

 #include <openssl/bio.h>

 BIO *BIO_find_type(BIO *b, int bio_type);
 BIO *BIO_next(BIO *b);
 int BIO_method_type(const BIO *b);

=head1 DESCRIPTION

The BIO_find_type() searches for a BIO of a given type in a chain, starting
at BIO B<b>. If B<type> is a specific type (such as B<BIO_TYPE_MEM>) then a search
is made for a BIO of that type. If B<type> is a general type (such as
B<BIO_TYPE_SOURCE_SINK>) then the next matching BIO of the given general type is
searched for. BIO_find_type() returns the next matching BIO or NULL if none is
found.

The following general types are defined:
B<BIO_TYPE_DESCRIPTOR>, B<BIO_TYPE_FILTER>, and B<BIO_TYPE_SOURCE_SINK>.

For a list of the specific types, see the B<openssl/bio.h> header file.

BIO_next() returns the next BIO in a chain. It can be used to traverse all BIOs
in a chain or used in conjunction with BIO_find_type() to find all BIOs of a
certain type.

BIO_method_type() returns the type of a BIO.

=head1 RETURN VALUES

BIO_find_type() returns a matching BIO or NULL for no match.

BIO_next() returns the next BIO in a chain.

BIO_method_type() returns the type of the BIO B<b>.

=head1 EXAMPLES

Traverse a chain looking for digest BIOs:

 BIO *btmp;

 btmp = in_bio; /* in_bio is chain to search through */
 do {
     btmp = BIO_find_type(btmp, BIO_TYPE_MD);
     if (btmp == NULL)
         break; /* Not found */
     /* btmp is a digest BIO, do something with it ...*/
     ...

     btmp = BIO_next(btmp);
 } while (btmp);


=head1 COPYRIGHT

Copyright 2000-2019 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>.

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