NAME¶
BIO_f_buffer - buffering BIO
SYNOPSIS¶
#include <openssl/bio.h>
BIO_METHOD * BIO_f_buffer(void);
#define BIO_get_buffer_num_lines(b) BIO_ctrl(b,BIO_C_GET_BUFF_NUM_LINES,0,NULL)
#define BIO_set_read_buffer_size(b,size) BIO_int_ctrl(b,BIO_C_SET_BUFF_SIZE,size,0)
#define BIO_set_write_buffer_size(b,size) BIO_int_ctrl(b,BIO_C_SET_BUFF_SIZE,size,1)
#define BIO_set_buffer_size(b,size) BIO_ctrl(b,BIO_C_SET_BUFF_SIZE,size,NULL)
#define BIO_set_buffer_read_data(b,buf,num) BIO_ctrl(b,BIO_C_SET_BUFF_READ_DATA,num,buf)
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() 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¶
Buffering BIOs implement
BIO_gets() by using
BIO_read() operations
on the next BIO in the chain. By prepending a buffering BIO to a chain it is
therefore possible to provide
BIO_gets() functionality 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() 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() returns the buffering BIO method.
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(3),
BIO_reset(3),
BIO_flush(3),
BIO_pop(3),
BIO_ctrl(3),
BIO_int_ctrl(3)