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
#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);
BIO_f_buffer() 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.
These functions, other than
BIO_f_buffer(), 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() 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(), 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.
BIO_f_buffer() 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.
bio(7),
BIO_reset(3),
BIO_flush(3),
BIO_pop(3),
BIO_ctrl(3).
Copyright 2000-2021 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>.