=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 and/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
first BIO then traverses the chain to the end (normally a source/sink
BIO).

=head1 SEE ALSO

TBA
