.\" $OpenBSD: BIO_f_buffer.3,v 1.11 2022/03/31 17:27:16 naddy Exp $ .\" OpenSSL 9b86974e Mar 19 12:32:14 2016 -0400 .\" .\" This file was written by Dr. Stephen Henson . .\" Copyright (c) 2000, 2010, 2015, 2016 The OpenSSL Project. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. All advertising materials mentioning features or use of this .\" software must display the following acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" .\" .\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to .\" endorse or promote products derived from this software without .\" prior written permission. For written permission, please contact .\" openssl-core@openssl.org. .\" .\" 5. Products derived from this software may not be called "OpenSSL" .\" nor may "OpenSSL" appear in their names without prior written .\" permission of the OpenSSL Project. .\" .\" 6. Redistributions of any form whatsoever must retain the following .\" acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" .\" .\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY .\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: March 31 2022 $ .Dt BIO_F_BUFFER 3 .Os .Sh NAME .Nm BIO_f_buffer , .Nm BIO_get_buffer_num_lines , .Nm BIO_set_read_buffer_size , .Nm BIO_set_write_buffer_size , .Nm BIO_set_buffer_size , .Nm BIO_set_buffer_read_data .Nd buffering BIO .Sh SYNOPSIS .In openssl/bio.h .Ft const BIO_METHOD * .Fo BIO_f_buffer .Fa void .Fc .Ft long .Fo BIO_get_buffer_num_lines .Fa "BIO *b" .Fc .Ft long .Fo BIO_set_read_buffer_size .Fa "BIO *b" .Fa "long size" .Fc .Ft long .Fo BIO_set_write_buffer_size .Fa "BIO *b" .Fa "long size" .Fc .Ft long .Fo BIO_set_buffer_size .Fa "BIO *b" .Fa "long size" .Fc .Fo BIO_set_buffer_read_data .Fa "BIO *b" .Fa "void *buf" .Fa "long num" .Fc .Sh DESCRIPTION .Fn BIO_f_buffer returns the buffering BIO method. .Pp 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 .Xr BIO_gets 3 and .Xr BIO_puts 3 are supported. .Pp Calling .Xr BIO_reset 3 on a buffering BIO clears any buffered data. .Pp .Fn BIO_get_buffer_num_lines returns the number of lines currently buffered. .Pp .Fn BIO_set_read_buffer_size , .Fn BIO_set_write_buffer_size , and .Fn BIO_set_buffer_size set the read, write or both read and write buffer sizes to .Fa size . The initial buffer size is .Dv DEFAULT_BUFFER_SIZE , currently 4096. Any attempt to reduce the buffer size below .Dv DEFAULT_BUFFER_SIZE is ignored. Any buffered data is cleared when the buffer is resized. .Pp .Fn BIO_set_buffer_read_data clears the read buffer and fills it with .Fa num bytes of .Fa buf . If .Fa num is larger than the current buffer size, the buffer is expanded. .Pp Except .Fn BIO_f_buffer , these functions are implemented as macros. .Pp Buffering BIOs implement .Xr BIO_gets 3 by using .Xr 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 .Xr BIO_gets 3 if the following BIOs do not support it (for example SSL BIOs). .Pp Data is only written to the next BIO in the chain when the write buffer fills or when .Xr BIO_flush 3 is called. It is therefore important to call .Xr BIO_flush 3 whenever any pending data should be written such as when removing a buffering BIO using .Xr BIO_pop 3 . .Xr BIO_flush 3 may need to be retried if the ultimate source/sink BIO is non-blocking. .Sh RETURN VALUES .Fn BIO_f_buffer returns the buffering BIO method. .Pp .Fn BIO_get_buffer_num_lines returns the number of lines buffered (may be 0). .Pp .Fn BIO_set_read_buffer_size , .Fn BIO_set_write_buffer_size , and .Fn BIO_set_buffer_size return 1 if the buffer was successfully resized or 0 for failure. .Pp .Fn BIO_set_buffer_read_data returns 1 if the data was set correctly or 0 if there was an error. .Sh SEE ALSO .Xr BIO_ctrl 3 , .Xr BIO_flush 3 , .Xr BIO_new 3 , .Xr BIO_pop 3 , .Xr BIO_reset 3 .Sh HISTORY .Fn BIO_f_buffer first appeared in SSLeay 0.6.0. .Fn BIO_get_buffer_num_lines and .Fn BIO_set_buffer_size first appeared in SSLeay 0.6.5. .Fn BIO_set_read_buffer_size and .Fn BIO_set_write_buffer_size first appeared in SSLeay 0.8.0. .Fn BIO_set_buffer_read_data first appeared in SSLeay 0.9.0. All these functions have been available since .Ox 2.4 .