NAME
BIO_f_buffer,
BIO_get_buffer_num_lines,
BIO_set_read_buffer_size,
BIO_set_write_buffer_size,
BIO_set_buffer_size,
BIO_set_buffer_read_data —
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()
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(3) and BIO_puts(3) are supported.
Calling BIO_reset(3) 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.
Buffering BIOs implement BIO_gets(3) by using BIO_read(3) operations on the next BIO in the chain. By prepending a buffering BIO to a chain it is therefore possible to provide the functionality of BIO_gets(3) if the following BIOs do not support it (for example SSL BIOs).
Data is only written to the next BIO in the chain when the write buffer fills or when BIO_flush(3) is called. It is therefore important to call BIO_flush(3) whenever any pending data should be written such as when removing a buffering BIO using BIO_pop(3). BIO_flush(3) may need to be retried if the ultimate source/sink BIO is non-blocking.
When a chain containing a
buffering BIO is copied with
BIO_dup_chain(3),
BIO_set_read_buffer_size()
and
BIO_set_write_buffer_size()
are called internally to automatically copy both buffer sizes from the
original BIO object to the new one.
BIO_ctrl(3) cmd arguments correspond to macros as follows:
| cmd constant | corresponding macro |
BIO_C_GET_BUFF_NUM_LINES |
BIO_get_buffer_num_lines() |
BIO_C_SET_BUFF_READ_DATA |
BIO_set_buffer_read_data() |
BIO_C_SET_BUFF_SIZE |
BIO_set_buffer_size() |
BIO_CTRL_FLUSH |
BIO_flush(3) |
BIO_CTRL_PENDING |
BIO_pending(3) |
BIO_CTRL_RESET |
BIO_reset(3) |
BIO_CTRL_WPENDING |
BIO_wpending(3) |
The cmd constant
BIO_C_SET_BUFF_SIZE is special. It is also used for
BIO_int_ctrl(3) with the following iarg
arguments:
| cmd constant | iarg | corresponding macro |
BIO_C_SET_BUFF_SIZE |
0 | BIO_set_read_buffer_size() |
| 1 | BIO_set_write_buffer_size() |
RETURN VALUES
BIO_f_buffer() returns the buffering BIO
method.
When called on a buffering BIO object,
BIO_method_type(3) returns the constant
BIO_TYPE_BUFFER and
BIO_method_name(3) returns a pointer to the static string
"buffer".
BIO_get_buffer_num_lines() returns the
number of lines buffered (may be 0).
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_ctrl(3), BIO_flush(3), BIO_new(3), BIO_pop(3), BIO_reset(3)
HISTORY
BIO_f_buffer() first appeared in SSLeay
0.6.0. BIO_get_buffer_num_lines() and
BIO_set_buffer_size() first appeared in SSLeay
0.6.5. BIO_set_read_buffer_size() and
BIO_set_write_buffer_size() first appeared in SSLeay
0.8.0. BIO_set_buffer_read_data() first appeared in
SSLeay 0.9.0. All these functions have been available since
OpenBSD 2.4.