| =pod |
| |
| =head1 NAME |
| |
| bio - Basic I/O abstraction |
| |
| =head1 SYNOPSIS |
| |
| =for comment generic |
| |
| #include <openssl/bio.h> |
| |
| =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). |
| |
| |
| Some BIOs (such as memory BIOs) can be used immediately after calling |
| BIO_new(). Others (such as file BIOs) need some additional initialization, |
| 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() on 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 EXAMPLES |
| |
| Create a memory BIO: |
| |
| BIO *mem = BIO_new(BIO_s_mem()); |
| |
| =head1 SEE ALSO |
| |
| L<BIO_ctrl(3)>, |
| L<BIO_f_base64(3)>, L<BIO_f_buffer(3)>, |
| L<BIO_f_cipher(3)>, L<BIO_f_md(3)>, |
| L<BIO_f_null(3)>, L<BIO_f_ssl(3)>, |
| L<BIO_find_type(3)>, L<BIO_new(3)>, |
| L<BIO_new_bio_pair(3)>, |
| L<BIO_push(3)>, L<BIO_read_ex(3)>, |
| L<BIO_s_accept(3)>, L<BIO_s_bio(3)>, |
| L<BIO_s_connect(3)>, L<BIO_s_fd(3)>, |
| L<BIO_s_file(3)>, L<BIO_s_mem(3)>, |
| L<BIO_s_null(3)>, L<BIO_s_socket(3)>, |
| L<BIO_set_callback(3)>, |
| L<BIO_should_retry(3)> |
| |
| =head1 COPYRIGHT |
| |
| Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved. |
| |
| Licensed under the OpenSSL license (the "License"). You may not use |
| this file except in compliance with the License. You can obtain a copy |
| in the file LICENSE in the source distribution or at |
| L<https://www.openssl.org/source/license.html>. |
| |
| =cut |
| |