Cryptography and SSL/TLS Toolkit



BIO_find_type, BIO_next, BIO_method_type - BIO chain traversal


 #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);


The BIO_find_type() searches for a BIO of a given type in a chain, starting at BIO b. If type is a specific type (such as BIO_TYPE_MEM) then a search is made for a BIO of that type. If type is a general type (such as 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: BIO_TYPE_DESCRIPTOR, BIO_TYPE_FILTER, and BIO_TYPE_SOURCE_SINK.

For a list of the specific types, see the 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.


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.


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);

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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