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BIO_FIND_TYPE(3) Library Functions Manual BIO_FIND_TYPE(3)

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);

#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

The function BIO_find_type() searches for a BIO of a given type in a chain, starting at BIO b. If bio_type is a specific type (such as BIO_TYPE_MEM), then a search is made for a BIO of that type. If bio_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.

Note: not all the 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.

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);

BIO_new(3)

BIO_method_type() first appeared in SSLeay 0.6.0. BIO_find_type() first appeared in SSLeay 0.6.6. Both functions have been available since OpenBSD 2.4.

BIO_next() first appeared in OpenSSL 0.9.6 and has been available since OpenBSD 2.9.

BIO_find_type() in OpenSSL 0.9.5a and earlier could not be safely passed a NULL pointer for the b argument.
March 27, 2018 OpenBSD-current