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#include <openssl/bio.h>
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A BIO is an I/O abstraction, it hides many of the underlying I/O
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details from an application. If an application uses a BIO for its
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I/O it can transparently handle SSL connections, unencrypted network
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connections and file I/O.
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There are two type of BIO, a source/sink BIO and a filter BIO.
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As its name implies a source/sink BIO is a source and/or sink of data,
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examples include a socket BIO and a file BIO.
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A filter BIO takes data from one BIO and passes it through to
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another, or the application. The data may be left unmodified (for
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example a message digest BIO) or translated (for example an
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encryption BIO). The effect of a filter BIO may change according
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to the I/O operation it is performing: for example an encryption
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BIO will encrypt data if it is being written to and decrypt data
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if it is being read from.
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BIOs can be joined together to form a chain (a single BIO is a chain
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with one component). A chain normally consist of one source/sink
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BIO and one or more filter BIOs. Data read from or written to the
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first BIO then traverses the chain to the end (normally a source/sink
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L<BIO_ctrl(3)|BIO_ctrl(3)>,
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L<BIO_f_base64(3)|BIO_f_base64(3)>, L<BIO_f_buffer(3)|BIO_f_buffer(3)>,
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L<BIO_f_cipher(3)|BIO_f_cipher(3)>, L<BIO_f_md(3)|BIO_f_md(3)>,
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L<BIO_f_null(3)|BIO_f_null(3)>, L<BIO_f_ssl(3)|BIO_f_ssl(3)>,
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L<BIO_find_type(3)|BIO_find_type(3)>, L<BIO_new(3)|BIO_new(3)>,
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L<BIO_new_bio_pair(3)|BIO_new_bio_pair(3)>,
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L<BIO_push(3)|BIO_push(3)>, L<BIO_read(3)|BIO_read(3)>,
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L<BIO_s_accept(3)|BIO_s_accept(3)>, L<BIO_s_bio(3)|BIO_s_bio(3)>,
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L<BIO_s_connect(3)|BIO_s_connect(3)>, L<BIO_s_fd(3)|BIO_s_fd(3)>,
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L<BIO_s_file(3)|BIO_s_file(3)>, L<BIO_s_mem(3)|BIO_s_mem(3)>,
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L<BIO_s_null(3)|BIO_s_null(3)>, L<BIO_s_socket(3)|BIO_s_socket(3)>,
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L<BIO_set_callback(3)|BIO_set_callback(3)>,
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L<BIO_should_retry(3)|BIO_should_retry(3)>