BIO_FIND_TYPE(3)

NAME
BIO_find_type, BIO_next, BIO_method_type - BIO chain traversal

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

DESCRIPTION
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.

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.

NOTES
BIO_next() was added to OpenSSL 0.9.6 to provide a 'clean' way to traverse a BIO chain or find multiple matches using BIO_find_type(). Previous versions had to use:

    next = bio->next_bio;

BUGS
BIO_find_type() in OpenSSL 0.9.5a and earlier could not be safely passed a NULL pointer for the b argument.

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);