bio(3) OpenSSL bio(3)
bio - I/O abstraction
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
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),
1.0.1e 2013-02-11 bio(3)