=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);

 #define BIO_method_type(b)             ((b)->method->type)

 #define BIO_TYPE_NONE          0
 #define BIO_TYPE_MEM           (1|0x0400)
 #define BIO_TYPE_FILE          (2|0x0400)

 #define BIO_TYPE_FD            (4|0x0400|0x0100)
 #define BIO_TYPE_SOCKET                (5|0x0400|0x0100)
 #define BIO_TYPE_NULL          (6|0x0400)
 #define BIO_TYPE_SSL           (7|0x0200)
 #define BIO_TYPE_MD            (8|0x0200)
 #define BIO_TYPE_BUFFER                (9|0x0200)
 #define BIO_TYPE_CIPHER                (10|0x0200)
 #define BIO_TYPE_BASE64                (11|0x0200)
 #define BIO_TYPE_CONNECT       (12|0x0400|0x0100)
 #define BIO_TYPE_ACCEPT                (13|0x0400|0x0100)
 #define BIO_TYPE_PROXY_CLIENT  (14|0x0200)
 #define BIO_TYPE_PROXY_SERVER  (15|0x0200)
 #define BIO_TYPE_NBIO_TEST     (16|0x0200)
 #define BIO_TYPE_NULL_FILTER   (17|0x0200)
 #define BIO_TYPE_BER           (18|0x0200)
 #define BIO_TYPE_BIO           (19|0x0400)

 #define BIO_TYPE_DESCRIPTOR    0x0100
 #define BIO_TYPE_FILTER                0x0200
 #define BIO_TYPE_SOURCE_SINK   0x0400

=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 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.

Note: not all the B<BIO_TYPE_*> types above have corresponding BIO implementations.

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 EXAMPLE

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 2000-2016 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
