1.\" $OpenBSD: BIO_f_buffer.3,v 1.3 2015/11/11 22:14:39 jmc Exp $ 2.\" 3.Dd $Mdocdate: November 11 2015 $ 4.Dt BIO_F_BUFFER 3 5.Os 6.Sh NAME 7.Nm BIO_f_buffer , 8.Nm BIO_get_buffer_num_lines , 9.Nm BIO_set_read_buffer_size , 10.Nm BIO_set_write_buffer_size , 11.Nm BIO_set_buffer_size , 12.Nm BIO_set_buffer_read_data 13.Nd buffering BIO 14.Sh SYNOPSIS 15.In openssl/bio.h 16.Ft BIO_METHOD * 17.Fo BIO_f_buffer 18.Fa void 19.Fc 20.Bd -literal 21#define BIO_get_buffer_num_lines(b) \e 22 BIO_ctrl(b,BIO_C_GET_BUFF_NUM_LINES,0,NULL) 23#define BIO_set_read_buffer_size(b,size) \e 24 BIO_int_ctrl(b,BIO_C_SET_BUFF_SIZE,size,0) 25#define BIO_set_write_buffer_size(b,size) \e 26 BIO_int_ctrl(b,BIO_C_SET_BUFF_SIZE,size,1) 27#define BIO_set_buffer_size(b,size) \e 28 BIO_ctrl(b,BIO_C_SET_BUFF_SIZE,size,NULL) 29#define BIO_set_buffer_read_data(b,buf,num) \e 30 BIO_ctrl(b,BIO_C_SET_BUFF_READ_DATA,num,buf) 31.Ed 32.Sh DESCRIPTION 33.Fn BIO_f_buffer 34returns the buffering BIO method. 35.Pp 36Data written to a buffering BIO is buffered and periodically written 37to the next BIO in the chain. 38Data read from a buffering BIO comes from an internal buffer 39which is filled from the next BIO in the chain. 40Both 41.Xr BIO_gets 3 42and 43.Xr BIO_puts 3 44are supported. 45.Pp 46Calling 47.Xr BIO_reset 3 48on a buffering BIO clears any buffered data. 49.Pp 50.Fn BIO_get_buffer_num_lines 51returns the number of lines currently buffered. 52.Pp 53.Fn BIO_set_read_buffer_size , 54.Fn BIO_set_write_buffer_size , 55and 56.Fn BIO_set_buffer_size 57set the read, write or both read and write buffer sizes to 58.Fa size . 59The initial buffer size is 60.Dv DEFAULT_BUFFER_SIZE , 61currently 4096. 62Any attempt to reduce the buffer size below 63.Dv DEFAULT_BUFFER_SIZE 64is ignored. 65Any buffered data is cleared when the buffer is resized. 66.Pp 67.Fn BIO_set_buffer_read_data 68clears the read buffer and fills it with 69.Fa num 70bytes of 71.Fa buf . 72If 73.Fa num 74is larger than the current buffer size the buffer is expanded. 75.Sh NOTES 76Buffering BIOs implement 77.Xr BIO_gets 3 78by using 79.Xr BIO_read 3 80operations on the next BIO in the chain. 81By prepending a buffering BIO to a chain 82it is therefore possible to provide 83.Xr BIO_gets 3 84functionality if the following BIOs do not support it (for example SSL BIOs). 85.Pp 86Data is only written to the next BIO in the chain 87when the write buffer fills or when 88.Xr BIO_flush 3 89is called. 90It is therefore important to call 91.Xr BIO_flush 3 92whenever any pending data should be written 93such as when removing a buffering BIO using 94.Xr BIO_pop 3 . 95.Xr BIO_flush 3 96may need to be retried if the ultimate source/sink BIO is non blocking. 97.Sh RETURN VALUES 98.Fn BIO_f_buffer 99returns the buffering BIO method. 100.Pp 101.Fn BIO_get_buffer_num_lines 102returns the number of lines buffered (may be 0). 103.Pp 104.Fn BIO_set_read_buffer_size , 105.Fn BIO_set_write_buffer_size , 106and 107.Fn BIO_set_buffer_size 108return 1 if the buffer was successfully resized or 0 for failure. 109.Pp 110.Fn BIO_set_buffer_read_data 111returns 1 if the data was set correctly or 0 if there was an error. 112.Sh SEE ALSO 113.Xr BIO 3 , 114.Xr BIO_ctrl 3 , 115.Xr BIO_flush 3 , 116.Xr BIO_pop 3 , 117.Xr BIO_reset 3 118