BIO_F_BUFFER(3ossl) OpenSSL BIO_F_BUFFER(3ossl)
NAME
BIO_get_buffer_num_lines, BIO_set_read_buffer_size,
BIO_set_write_buffer_size, BIO_set_buffer_size,
BIO_set_buffer_read_data, BIO_f_buffer - buffering BIO
SYNOPSIS
#include <openssl/bio.h>
const BIO_METHOD *BIO_f_buffer(void);
long BIO_get_buffer_num_lines(BIO *b);
long BIO_set_read_buffer_size(BIO *b, long size);
long BIO_set_write_buffer_size(BIO *b, long size);
long BIO_set_buffer_size(BIO *b, long size);
long BIO_set_buffer_read_data(BIO *b, void *buf, long num);
DESCRIPTION
BIO_f_buffer(3) returns the buffering BIO method.
Data written to a buffering BIO is buffered and periodically written to
the next BIO in the chain. Data read from a buffering BIO comes from an
internal buffer which is filled from the next BIO in the chain. Both
BIO_gets() and BIO_puts() are supported.
Calling BIO_reset() on a buffering BIO clears any buffered data.
BIO_get_buffer_num_lines() returns the number of lines currently
buffered.
BIO_set_read_buffer_size(), BIO_set_write_buffer_size() and
BIO_set_buffer_size() set the read, write or both read and write buffer
sizes to size. The initial buffer size is DEFAULT_BUFFER_SIZE,
currently 4096. Any attempt to reduce the buffer size below
DEFAULT_BUFFER_SIZE is ignored. Any buffered data is cleared when the
buffer is resized.
BIO_set_buffer_read_data() clears the read buffer and fills it with num
bytes of buf. If num is larger than the current buffer size the buffer
is expanded.
NOTES
These functions, other than BIO_f_buffer(3), are implemented as macros.
Buffering BIOs implement BIO_read_ex() and BIO_gets() by using
BIO_read_ex() operations on the next BIO in the chain and storing the
result in an internal buffer, from which bytes are given back to the
caller as appropriate for the call; a BIO_gets() is guaranteed to give
the caller a whole line, and BIO_read_ex() is guaranteed to give the
caller the number of bytes it asks for, unless there's an error or end
of communication is reached in the next BIO. By prepending a buffering
BIO to a chain it is therefore possible to provide BIO_gets() or exact
size BIO_read_ex() functionality if the following BIOs do not support
it.
Do not add more than one BIO_f_buffer(3) to a BIO chain. The result of
doing so will force a full read of the size of the internal buffer of
the top BIO_f_buffer(3), which is 4 KiB at a minimum.
Data is only written to the next BIO in the chain when the write buffer
fills or when BIO_flush() is called. It is therefore important to call
BIO_flush() whenever any pending data should be written such as when
removing a buffering BIO using BIO_pop(). BIO_flush() may need to be
retried if the ultimate source/sink BIO is non blocking.
RETURN VALUES
BIO_f_buffer(3) returns the buffering BIO method.
BIO_get_buffer_num_lines() returns the number of lines buffered (may be
0) or a negative value in case of errors.
BIO_set_read_buffer_size(), BIO_set_write_buffer_size() and
BIO_set_buffer_size() return 1 if the buffer was successfully resized
or <=0 for failure.
BIO_set_buffer_read_data() returns 1 if the data was set correctly or
<=0 if there was an error.
SEE ALSO
bio(7), BIO_reset(3), BIO_flush(3), BIO_pop(3), BIO_ctrl(3).
COPYRIGHT
Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (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
<https://www.openssl.org/source/license.html>.
3.3.2 2024-09-04 BIO_F_BUFFER(3ossl)
openssl 3.3.2 - Generated Thu Sep 5 18:38:55 CDT 2024