1BIO(7ossl)                          OpenSSL                         BIO(7ossl)
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NAME

6       bio - Basic I/O abstraction
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SYNOPSIS

9        #include <openssl/bio.h>
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DESCRIPTION

12       A BIO is an I/O abstraction, it hides many of the underlying I/O
13       details from an application. If an application uses a BIO for its I/O
14       it can transparently handle SSL connections, unencrypted network
15       connections and file I/O.
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17       There are two types of BIO, a source/sink BIO and a filter BIO.
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19       As its name implies a source/sink BIO is a source and/or sink of data,
20       examples include a socket BIO and a file BIO.
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22       A filter BIO takes data from one BIO and passes it through to another,
23       or the application. The data may be left unmodified (for example a
24       message digest BIO) or translated (for example an encryption BIO). The
25       effect of a filter BIO may change according to the I/O operation it is
26       performing: for example an encryption BIO will encrypt data if it is
27       being written to and decrypt data if it is being read from.
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29       BIOs can be joined together to form a chain (a single BIO is a chain
30       with one component). A chain normally consists of one source/sink BIO
31       and one or more filter BIOs. Data read from or written to the first BIO
32       then traverses the chain to the end (normally a source/sink BIO).
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34       Some BIOs (such as memory BIOs) can be used immediately after calling
35       BIO_new(). Others (such as file BIOs) need some additional
36       initialization, and frequently a utility function exists to create and
37       initialize such BIOs.
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39       If BIO_free() is called on a BIO chain it will only free one BIO
40       resulting in a memory leak.
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42       Calling BIO_free_all() on a single BIO has the same effect as calling
43       BIO_free() on it other than the discarded return value.
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45       Normally the type argument is supplied by a function which returns a
46       pointer to a BIO_METHOD. There is a naming convention for such
47       functions: a source/sink BIO typically starts with BIO_s_ and a filter
48       BIO with BIO_f_.
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EXAMPLES

51       Create a memory BIO:
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53        BIO *mem = BIO_new(BIO_s_mem());
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SEE ALSO

56       BIO_ctrl(3), BIO_f_base64(3), BIO_f_buffer(3), BIO_f_cipher(3),
57       BIO_f_md(3), BIO_f_null(3), BIO_f_ssl(3), BIO_f_readbuffer(3),
58       BIO_find_type(3), BIO_new(3), BIO_new_bio_pair(3), BIO_push(3),
59       BIO_read_ex(3), BIO_s_accept(3), BIO_s_bio(3), BIO_s_connect(3),
60       BIO_s_fd(3), BIO_s_file(3), BIO_s_mem(3), BIO_s_null(3),
61       BIO_s_socket(3), BIO_set_callback(3), BIO_should_retry(3)
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64       Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
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66       Licensed under the Apache License 2.0 (the "License").  You may not use
67       this file except in compliance with the License.  You can obtain a copy
68       in the file LICENSE in the source distribution or at
69       <https://www.openssl.org/source/license.html>.
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733.0.9                             2023-07-27                        BIO(7ossl)
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