1.Dd July 17, 2014 2.Dt BIO_F_BUFFER 3 3.Os 4.Sh NAME 5.Nm BIO_f_buffer 6.Nd buffering BIO 7.Sh SYNOPSIS 8.In openssl/bio.h 9.Ft BIO_METHOD * 10.Fo BIO_f_buffer 11.Fa void 12.Fc 13.Bd -literal 14#define BIO_get_buffer_num_lines(b) \e 15 BIO_ctrl(b,BIO_C_GET_BUFF_NUM_LINES,0,NULL) 16#define BIO_set_read_buffer_size(b,size) \e 17 BIO_int_ctrl(b,BIO_C_SET_BUFF_SIZE,size,0) 18#define BIO_set_write_buffer_size(b,size) \e 19 BIO_int_ctrl(b,BIO_C_SET_BUFF_SIZE,size,1) 20#define BIO_set_buffer_size(b,size) \e 21 BIO_ctrl(b,BIO_C_SET_BUFF_SIZE,size,NULL) 22#define BIO_set_buffer_read_data(b,buf,num) \e 23 BIO_ctrl(b,BIO_C_SET_BUFF_READ_DATA,num,buf) 24.Ed 25.Sh DESCRIPTION 26.Fn BIO_f_buffer 27returns the buffering BIO method. 28.Pp 29Data written to a buffering BIO is buffered and periodically written 30to the next BIO in the chain. 31Data read from a buffering BIO comes from an internal buffer 32which is filled from the next BIO in the chain. 33Both 34.Xr BIO_gets 3 35and 36.Xr BIO_puts 3 37are supported. 38.Pp 39Calling 40.Xr BIO_reset 3 41on a buffering BIO clears any buffered data. 42.Pp 43.Fn BIO_get_buffer_num_lines 44returns the number of lines currently buffered. 45.Pp 46.Fn BIO_set_read_buffer_size , 47.Fn BIO_set_write_buffer_size , 48and 49.Fn BIO_set_buffer_size 50set the read, write or both read and write buffer sizes to 51.Fa size . 52The initial buffer size is 53.Dv DEFAULT_BUFFER_SIZE , 54currently 4096. 55Any attempt to reduce the buffer size below 56.Dv DEFAULT_BUFFER_SIZE 57is ignored. 58Any buffered data is cleared when the buffer is resized. 59.Pp 60.Fn BIO_set_buffer_read_data 61clears the read buffer and fills it with 62.Fa num 63bytes of 64.Fa buf . 65If 66.Fa num 67is larger than the current buffer size the buffer is expanded. 68.Sh NOTES 69Buffering BIOs implement 70.Xr BIO_gets 3 71by using 72.Xr BIO_read 3 73operations on the next BIO in the chain. 74By prepending a buffering BIO to a chain 75it is therefore possible to provide 76.Xr BIO_gets 3 77functionality if the following BIOs do not support it (for example SSL BIOs). 78.Pp 79Data is only written to the next BIO in the chain 80when the write buffer fills or when 81.Xr BIO_flush 3 82is called. 83It is therefore important to call 84.Xr BIO_flush 3 85whenever any pending data should be written 86such as when removing a buffering BIO using 87.Xr BIO_pop 3 . 88.Xr BIO_flush 3 89may need to be retried if the ultimate source/sink BIO is non blocking. 90.Sh RETURN VALUES 91.Fn BIO_f_buffer 92returns the buffering BIO method. 93.Pp 94.Fn BIO_get_buffer_num_lines 95returns the number of lines buffered (may be 0). 96.Pp 97.Fn BIO_set_read_buffer_size , 98.Fn BIO_set_write_buffer_size , 99and 100.Fn BIO_set_buffer_size 101return 1 if the buffer was successfully resized or 0 for failure. 102.Pp 103.Fn BIO_set_buffer_read_data 104returns 1 if the data was set correctly or 0 if there was an error. 105.Sh SEE ALSO 106.Xr BIO 3 , 107.Xr BIO_ctrl 3 , 108.Xr BIO_flush 3 , 109.Xr BIO_pop 3 , 110.Xr BIO_reset 3 111