| lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame] | 1 | =pod |
| 2 | |
| 3 | =head1 NAME |
| 4 | |
| 5 | bio - Basic I/O abstraction |
| 6 | |
| 7 | =head1 SYNOPSIS |
| 8 | |
| 9 | =for comment generic |
| 10 | |
| 11 | #include <openssl/bio.h> |
| 12 | |
| 13 | =head1 DESCRIPTION |
| 14 | |
| 15 | A BIO is an I/O abstraction, it hides many of the underlying I/O |
| 16 | details from an application. If an application uses a BIO for its |
| 17 | I/O it can transparently handle SSL connections, unencrypted network |
| 18 | connections and file I/O. |
| 19 | |
| 20 | There are two type of BIO, a source/sink BIO and a filter BIO. |
| 21 | |
| 22 | As its name implies a source/sink BIO is a source and/or sink of data, |
| 23 | examples include a socket BIO and a file BIO. |
| 24 | |
| 25 | A filter BIO takes data from one BIO and passes it through to |
| 26 | another, or the application. The data may be left unmodified (for |
| 27 | example a message digest BIO) or translated (for example an |
| 28 | encryption BIO). The effect of a filter BIO may change according |
| 29 | to the I/O operation it is performing: for example an encryption |
| 30 | BIO will encrypt data if it is being written to and decrypt data |
| 31 | if it is being read from. |
| 32 | |
| 33 | BIOs can be joined together to form a chain (a single BIO is a chain |
| 34 | with one component). A chain normally consist of one source/sink |
| 35 | BIO and one or more filter BIOs. Data read from or written to the |
| 36 | first BIO then traverses the chain to the end (normally a source/sink |
| 37 | BIO). |
| 38 | |
| 39 | |
| 40 | Some BIOs (such as memory BIOs) can be used immediately after calling |
| 41 | BIO_new(). Others (such as file BIOs) need some additional initialization, |
| 42 | and frequently a utility function exists to create and initialize such BIOs. |
| 43 | |
| 44 | If BIO_free() is called on a BIO chain it will only free one BIO resulting |
| 45 | in a memory leak. |
| 46 | |
| 47 | Calling BIO_free_all() on a single BIO has the same effect as calling |
| 48 | BIO_free() on it other than the discarded return value. |
| 49 | |
| 50 | Normally the B<type> argument is supplied by a function which returns a |
| 51 | pointer to a BIO_METHOD. There is a naming convention for such functions: |
| 52 | a source/sink BIO is normally called BIO_s_*() and a filter BIO |
| 53 | BIO_f_*(); |
| 54 | |
| 55 | =head1 EXAMPLES |
| 56 | |
| 57 | Create a memory BIO: |
| 58 | |
| 59 | BIO *mem = BIO_new(BIO_s_mem()); |
| 60 | |
| 61 | =head1 SEE ALSO |
| 62 | |
| 63 | L<BIO_ctrl(3)>, |
| 64 | L<BIO_f_base64(3)>, L<BIO_f_buffer(3)>, |
| 65 | L<BIO_f_cipher(3)>, L<BIO_f_md(3)>, |
| 66 | L<BIO_f_null(3)>, L<BIO_f_ssl(3)>, |
| 67 | L<BIO_find_type(3)>, L<BIO_new(3)>, |
| 68 | L<BIO_new_bio_pair(3)>, |
| 69 | L<BIO_push(3)>, L<BIO_read_ex(3)>, |
| 70 | L<BIO_s_accept(3)>, L<BIO_s_bio(3)>, |
| 71 | L<BIO_s_connect(3)>, L<BIO_s_fd(3)>, |
| 72 | L<BIO_s_file(3)>, L<BIO_s_mem(3)>, |
| 73 | L<BIO_s_null(3)>, L<BIO_s_socket(3)>, |
| 74 | L<BIO_set_callback(3)>, |
| 75 | L<BIO_should_retry(3)> |
| 76 | |
| 77 | =head1 COPYRIGHT |
| 78 | |
| 79 | Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved. |
| 80 | |
| 81 | Licensed under the OpenSSL license (the "License"). You may not use |
| 82 | this file except in compliance with the License. You can obtain a copy |
| 83 | in the file LICENSE in the source distribution or at |
| 84 | L<https://www.openssl.org/source/license.html>. |
| 85 | |
| 86 | =cut |
| 87 | |