Add docs for BIO_find_type() and friends.

Added function BIO_next() otherwise you can't
traverse a chain without accessing BIO internals.

crypto/bio/bio.h

@@ -524,6 +524,7 @@ BIO *	BIO_push(BIO *b,BIO *append);
 BIO *	BIO_pop(BIO *b);
 void	BIO_free_all(BIO *a);
 BIO *	BIO_find_type(BIO *b,int bio_type);
+BIO *	BIO_next(BIO *b);
 BIO *	BIO_get_retry_BIO(BIO *bio, int *reason);
 int	BIO_get_retry_reason(BIO *bio);
 BIO *	BIO_dup_chain(BIO *in);

crypto/bio/bio_lib.c

@@ -436,6 +436,12 @@ BIO *BIO_find_type(BIO *bio, int type)
 	return(NULL);
 	}
 
+BIO *BIO_next(BIO *b)
+	{
+	if(!b) return NULL;
+	return b->next_bio;
+	}
+
 void BIO_free_all(BIO *bio)
 	{
 	BIO *b;

crypto/pkcs7/pk7_doit.c

@@ -534,7 +534,7 @@ int PKCS7_dataFinal(PKCS7 *p7, BIO *bio)
 				if (EVP_MD_CTX_type(mdc) == j)
 					break;
 				else
-					btmp=btmp->next_bio;
+					btmp=BIO_next(btmp);
 				}
 			
 			/* We now have the EVP_MD_CTX, lets do the
@@ -726,7 +726,7 @@ int PKCS7_signatureVerify(BIO *bio, PKCS7 *p7, PKCS7_SIGNER_INFO *si,
 			}
 		if (EVP_MD_CTX_type(mdc) == md_type)
 			break;
-		btmp=btmp->next_bio;	
+		btmp=BIO_next(btmp);
 		}
 
 	/* mdc is the digest ctx that we want, unless there are attributes,

doc/crypto/BIO_find_type.pod

@@ -0,0 +1,93 @@
+=pod
+
+=head1 NAME
+
+	BIO_find_type, BIO_next - 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 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;
+
+=head1 EXAMPLE
+
+Traverse a chain looking for digest BIOs:
+
+ BIO *btmp;
+ btmp = in_bio;	/* in_bio is chain to search through */
+
+ for(;;) {
+ 	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);
+ } 
+
+
+=head1 SEE ALSO
+
+TBA