SYNOPSIS
        #include <openssl/bio.h>

       TBA

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).

SEE ALSO
       bio_ctrl(3), bio_f_base64(3), bio_f_buffer(3), bio_f_cipher(3),
       bio_f_md(3), bio_f_null(3), bio_f_ssl(3), bio_find_type(3), bio_new(3),
       bio_new_bio_pair(3), bio_push(3), bio_read(3), bio_s_accept(3),
       bio_s_bio(3), bio_s_connect(3), bio_s_fd(3), bio_s_file(3),
       bio_s_mem(3), bio_s_null(3), bio_s_socket(3), bio_set_callback(3),
       bio_should_retry(3)