Some BIO docs, incomplete, more to follow.

=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

=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

=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