mirror of https://github.com/openssl/openssl
104 lines
3.5 KiB
Plaintext
104 lines
3.5 KiB
Plaintext
=pod
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=head1 NAME
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BIO_get_buffer_num_lines,
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BIO_set_read_buffer_size,
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BIO_set_write_buffer_size,
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BIO_set_buffer_size,
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BIO_set_buffer_read_data,
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BIO_f_buffer
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- buffering BIO
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=head1 SYNOPSIS
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#include <openssl/bio.h>
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const BIO_METHOD *BIO_f_buffer(void);
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long BIO_get_buffer_num_lines(BIO *b);
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long BIO_set_read_buffer_size(BIO *b, long size);
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long BIO_set_write_buffer_size(BIO *b, long size);
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long BIO_set_buffer_size(BIO *b, long size);
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long BIO_set_buffer_read_data(BIO *b, void *buf, long num);
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=head1 DESCRIPTION
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BIO_f_buffer() returns the buffering BIO method.
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Data written to a buffering BIO is buffered and periodically written
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to the next BIO in the chain. Data read from a buffering BIO comes from
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an internal buffer which is filled from the next BIO in the chain.
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Both BIO_gets() and BIO_puts() are supported.
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Calling BIO_reset() on a buffering BIO clears any buffered data.
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BIO_get_buffer_num_lines() returns the number of lines currently buffered.
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BIO_set_read_buffer_size(), BIO_set_write_buffer_size() and BIO_set_buffer_size()
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set the read, write or both read and write buffer sizes to B<size>. The initial
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buffer size is DEFAULT_BUFFER_SIZE, currently 4096. Any attempt to reduce the
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buffer size below DEFAULT_BUFFER_SIZE is ignored. Any buffered data is cleared
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when the buffer is resized.
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BIO_set_buffer_read_data() clears the read buffer and fills it with B<num>
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bytes of B<buf>. If B<num> is larger than the current buffer size the buffer
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is expanded.
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=head1 NOTES
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These functions, other than BIO_f_buffer(), are implemented as macros.
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Buffering BIOs implement BIO_read_ex() and BIO_gets() by using
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BIO_read_ex() operations on the next BIO in the chain and storing the
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result in an internal buffer, from which bytes are given back to the
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caller as appropriate for the call; a BIO_gets() is guaranteed to give
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the caller a whole line, and BIO_read_ex() is guaranteed to give the
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caller the number of bytes it asks for, unless there's an error or end
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of communication is reached in the next BIO. By prepending a
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buffering BIO to a chain it is therefore possible to provide
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BIO_gets() or exact size BIO_read_ex() functionality if the following
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BIOs do not support it.
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Do not add more than one BIO_f_buffer() to a BIO chain. The result of
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doing so will force a full read of the size of the internal buffer of
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the top BIO_f_buffer(), which is 4 KiB at a minimum.
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Data is only written to the next BIO in the chain when the write buffer fills
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or when BIO_flush() is called. It is therefore important to call BIO_flush()
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whenever any pending data should be written such as when removing a buffering
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BIO using BIO_pop(). BIO_flush() may need to be retried if the ultimate
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source/sink BIO is non blocking.
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=head1 RETURN VALUES
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BIO_f_buffer() returns the buffering BIO method.
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BIO_get_buffer_num_lines() returns the number of lines buffered (may be 0) or
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a negative value in case of errors.
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BIO_set_read_buffer_size(), BIO_set_write_buffer_size() and BIO_set_buffer_size()
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return 1 if the buffer was successfully resized or <=0 for failure.
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BIO_set_buffer_read_data() returns 1 if the data was set correctly or <=0 if
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there was an error.
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=head1 SEE ALSO
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L<bio(7)>,
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L<BIO_reset(3)>,
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L<BIO_flush(3)>,
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L<BIO_pop(3)>,
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L<BIO_ctrl(3)>.
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=head1 COPYRIGHT
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Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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