1.\" $OpenBSD: BIO_f_buffer.3,v 1.10 2018/05/01 17:05:05 schwarze Exp $ 2.\" OpenSSL 9b86974e Mar 19 12:32:14 2016 -0400 3.\" 4.\" This file was written by Dr. Stephen Henson <steve@openssl.org>. 5.\" Copyright (c) 2000, 2010, 2015, 2016 The OpenSSL Project. 6.\" All rights reserved. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in 17.\" the documentation and/or other materials provided with the 18.\" distribution. 19.\" 20.\" 3. All advertising materials mentioning features or use of this 21.\" software must display the following acknowledgment: 22.\" "This product includes software developed by the OpenSSL Project 23.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 24.\" 25.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 26.\" endorse or promote products derived from this software without 27.\" prior written permission. For written permission, please contact 28.\" openssl-core@openssl.org. 29.\" 30.\" 5. Products derived from this software may not be called "OpenSSL" 31.\" nor may "OpenSSL" appear in their names without prior written 32.\" permission of the OpenSSL Project. 33.\" 34.\" 6. Redistributions of any form whatsoever must retain the following 35.\" acknowledgment: 36.\" "This product includes software developed by the OpenSSL Project 37.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 38.\" 39.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 40.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 41.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 42.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 43.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 44.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 45.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 46.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 47.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 48.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 49.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 50.\" OF THE POSSIBILITY OF SUCH DAMAGE. 51.\" 52.Dd $Mdocdate: May 1 2018 $ 53.Dt BIO_F_BUFFER 3 54.Os 55.Sh NAME 56.Nm BIO_f_buffer , 57.Nm BIO_get_buffer_num_lines , 58.Nm BIO_set_read_buffer_size , 59.Nm BIO_set_write_buffer_size , 60.Nm BIO_set_buffer_size , 61.Nm BIO_set_buffer_read_data 62.Nd buffering BIO 63.Sh SYNOPSIS 64.In openssl/bio.h 65.Ft const BIO_METHOD * 66.Fo BIO_f_buffer 67.Fa void 68.Fc 69.Ft long 70.Fo BIO_get_buffer_num_lines 71.Fa "BIO *b" 72.Fc 73.Ft long 74.Fo BIO_set_read_buffer_size 75.Fa "BIO *b" 76.Fa "long size" 77.Fc 78.Ft long 79.Fo BIO_set_write_buffer_size 80.Fa "BIO *b" 81.Fa "long size" 82.Fc 83.Ft long 84.Fo BIO_set_buffer_size 85.Fa "BIO *b" 86.Fa "long size" 87.Fc 88.Fo BIO_set_buffer_read_data 89.Fa "BIO *b" 90.Fa "void *buf" 91.Fa "long num" 92.Fc 93.Sh DESCRIPTION 94.Fn BIO_f_buffer 95returns the buffering BIO method. 96.Pp 97Data written to a buffering BIO is buffered and periodically written 98to the next BIO in the chain. 99Data read from a buffering BIO comes from an internal buffer 100which is filled from the next BIO in the chain. 101Both 102.Xr BIO_gets 3 103and 104.Xr BIO_puts 3 105are supported. 106.Pp 107Calling 108.Xr BIO_reset 3 109on a buffering BIO clears any buffered data. 110.Pp 111.Fn BIO_get_buffer_num_lines 112returns the number of lines currently buffered. 113.Pp 114.Fn BIO_set_read_buffer_size , 115.Fn BIO_set_write_buffer_size , 116and 117.Fn BIO_set_buffer_size 118set the read, write or both read and write buffer sizes to 119.Fa size . 120The initial buffer size is 121.Dv DEFAULT_BUFFER_SIZE , 122currently 4096. 123Any attempt to reduce the buffer size below 124.Dv DEFAULT_BUFFER_SIZE 125is ignored. 126Any buffered data is cleared when the buffer is resized. 127.Pp 128.Fn BIO_set_buffer_read_data 129clears the read buffer and fills it with 130.Fa num 131bytes of 132.Fa buf . 133If 134.Fa num 135is larger than the current buffer size the buffer is expanded. 136.Pp 137Except 138.Fn BIO_f_buffer , 139these functions are implemented as macros. 140.Pp 141Buffering BIOs implement 142.Xr BIO_gets 3 143by using 144.Xr BIO_read 3 145operations on the next BIO in the chain. 146By prepending a buffering BIO to a chain 147it is therefore possible to provide the functionality of 148.Xr BIO_gets 3 149if the following BIOs do not support it (for example SSL BIOs). 150.Pp 151Data is only written to the next BIO in the chain 152when the write buffer fills or when 153.Xr BIO_flush 3 154is called. 155It is therefore important to call 156.Xr BIO_flush 3 157whenever any pending data should be written 158such as when removing a buffering BIO using 159.Xr BIO_pop 3 . 160.Xr BIO_flush 3 161may need to be retried if the ultimate source/sink BIO is non-blocking. 162.Sh RETURN VALUES 163.Fn BIO_f_buffer 164returns the buffering BIO method. 165.Pp 166.Fn BIO_get_buffer_num_lines 167returns the number of lines buffered (may be 0). 168.Pp 169.Fn BIO_set_read_buffer_size , 170.Fn BIO_set_write_buffer_size , 171and 172.Fn BIO_set_buffer_size 173return 1 if the buffer was successfully resized or 0 for failure. 174.Pp 175.Fn BIO_set_buffer_read_data 176returns 1 if the data was set correctly or 0 if there was an error. 177.Sh SEE ALSO 178.Xr BIO_ctrl 3 , 179.Xr BIO_flush 3 , 180.Xr BIO_new 3 , 181.Xr BIO_pop 3 , 182.Xr BIO_reset 3 183.Sh HISTORY 184.Fn BIO_f_buffer 185first appeared in SSLeay 0.6.0. 186.Fn BIO_get_buffer_num_lines 187and 188.Fn BIO_set_buffer_size 189first appeared in SSLeay 0.6.5. 190.Fn BIO_set_read_buffer_size 191and 192.Fn BIO_set_write_buffer_size 193first appeared in SSLeay 0.8.0. 194.Fn BIO_set_buffer_read_data 195first appeared in SSLeay 0.9.0. 196All these functions have been available since 197.Ox 2.4 . 198