Some BIO docs, incomplete, more to follow.

Hmmm I didn't realise BIO_pop() did that:
isn't source wonderful?

doc/crypto/BIO_new.pod

@@ -0,0 +1,65 @@
+=pod
+
+=head1 NAME
+
+	BIO_new, BIO_set, BIO_free, BIO_vfree, BIO_free_all - BIO allocation and freeing functions
+
+=head1 SYNOPSIS
+
+ #include <openssl/bio.h>
+
+ BIO *	BIO_new(BIO_METHOD *type);
+ int	BIO_set(BIO *a,BIO_METHOD *type);
+ int	BIO_free(BIO *a);
+ void	BIO_vfree(BIO *a);
+ void	BIO_free_all(BIO *a);
+
+=head1 DESCRIPTION
+
+The BIO_new() function returns a new BIO using method B<type>.
+
+BIO_set() sets the method of an already existing BIO.
+
+BIO_free() frees up a single BIO, BIO_vfree() also frees up a single BIO
+but it does not return a value. Calling BIO_free() may also have some effect
+on the underlying I/O structure, for example it may close the file being
+referred to under certain circumstances. For more details see the individual
+BIO_METHOD descriptions.
+
+BIO_free_all() frees up an entire BIO chain, it does not halt if an error
+occurs freeing up an individual BIO in the chain.
+
+=head1 RETURN VALUES
+
+BIO_new() returns a newly created BIO or NULL if the call fails.
+
+BIO_set(), BIO_free() return 1 for success and 0 for failure.
+
+BIO_free_all() and BIO_vfree() do not return values.
+
+=head1 NOTES
+
+Some BIOs (such as memory BIOs) can be used immediately after calling
+BIO_new(). Others (such as file BIOs) need some additional initialisation,
+and frequently a utility function exists to create and initialize such BIOs.
+
+If BIO_free() is called on a BIO chain it will only free one BIO resulting
+in a memory leak.
+
+Calling BIO_free_all() a single BIO has the same effect as calling BIO_free()
+on it other than the discarded return value.
+
+Normally the B<type> argument is supplied by a function which returns a
+pointer to a BIO_METHOD. There is a naming convention for such functions:
+a source/sink BIO is normally called BIO_s_*() and a filter BIO
+BIO_f_*();
+
+=head1 EXAMPLE
+
+Create a memory BIO:
+
+ BIO *mem = BIO_new(BIO_s_mem());
+
+=head1 SEE ALSO
+
+TBA

doc/crypto/BIO_push.pod

@@ -0,0 +1,69 @@
+=pod
+
+=head1 NAME
+
+	BIO_push, BIO_pop - add and remove BIOs from a chain.
+
+=head1 SYNOPSIS
+
+ #include <openssl/bio.h>
+
+ BIO *	BIO_push(BIO *b,BIO *append);
+ BIO *	BIO_pop(BIO *b);
+
+=head1 DESCRIPTION
+
+The BIO_push() function appends the BIO B<append> to B<b>, it returns
+B<b>.
+
+BIO_pop() removes the BIO B<b> from a chain and returns the next BIO
+in the chain, or NULL if there is no next BIO. The removed BIO then
+becomes a single BIO with no association with the original chain,
+it can thus be freed or attached to a different chain.
+
+=head1 NOTES
+
+The names of these functions are perhaps a little misleading. BIO_push()
+joins two BIO chains whereas BIO_pop() deletes a single BIO from a chain,
+the deleted BIO does not need to be at the end of a chain.
+
+The process of calling BIO_push() and BIO_pop() on a BIO may have additional
+consequences (a control call is made to the affected BIOs) any effects will
+be noted in the descriptions of individual BIOs.
+
+=head1 EXAMPLES
+
+For these examples suppose B<md1> and B<md2> are digest BIOs, B<b64> is
+a base64 BIO and B<f> is a file BIO.
+
+If the call:
+
+ BIO_push(b64, f);
+
+is made then the new chain will be B<b64-chain>. After making the calls
+
+ BIO_push(md2, b64);
+ BIO_push(md1, md2);
+
+the new chain is B<md1-md2-b64-f>. Data written to B<md1> will be digested
+by B<md1> and B<md2>, B<base64> encoded and written to B<f>.
+
+It should be noted that reading causes data to pass in the reverse
+direction, that is data is read from B<f>, base64 B<decoded> and digested
+by B<md1> and B<md2>. If the call:
+
+ BIO_pop(md2);
+
+The call will return B<b64> and the new chain will be B<md1-b64-f> data can
+be written to B<md1> as before.
+
+=head1 RETURN VALUES
+
+BIO_push() returns the end of the chain, B<b>.
+
+BIO_pop() returns the next BIO in the chain, or NULL if there is no next
+BIO.
+
+=head1 SEE ALSO
+
+TBA

doc/crypto/bio.pod

@@ -0,0 +1,42 @@
+=pod
+
+=head1 NAME
+
+bio - I/O abstraction
+
+=head1 SYNOPSIS
+
+ #include <openssl/bio.h>
+
+TBA
+
+
+=head1 DESCRIPTION
+
+A BIO is an I/O abstraction, it hides many of the underlying I/O
+details from an application. If an application uses a BIO for its
+I/O it can transparently handle SSL connections, unencrypted network
+connections and file I/O.
+
+There are two type of BIO, a source/sink BIO and a filter BIO.
+
+As its name implies a source/sink BIO is a source or sink of data,
+examples include a socket BIO and a file BIO.
+
+A filter BIO takes data from one BIO and passes it through to
+another, or the application. The data may be left unmodified (for
+example a message digest BIO) or translated (for example an
+encryption BIO). The effect of a filter BIO may change according
+to the I/O operation it is performing: for example an encryption
+BIO will encrypt data if it is being written to and decrypt data
+if it is being read from.
+
+BIOs can be joined together to form a chain (a single BIO is a chain
+with one component). A chain normally consist of one source/sink
+BIO and one or more filter BIOs. Data read from or written to the
+end BIO then traverses the chain to the end (normally a source/sink
+BIO).
+
+=head1 SEE ALSO
+
+TBA