1=pod 2 3=head1 NAME 4 5BIO_get_buffer_num_lines, 6BIO_set_read_buffer_size, 7BIO_set_write_buffer_size, 8BIO_set_buffer_size, 9BIO_set_buffer_read_data, 10BIO_f_buffer 11- buffering BIO 12 13=head1 SYNOPSIS 14 15 #include <openssl/bio.h> 16 17 const BIO_METHOD *BIO_f_buffer(void); 18 19 long BIO_get_buffer_num_lines(BIO *b); 20 long BIO_set_read_buffer_size(BIO *b, long size); 21 long BIO_set_write_buffer_size(BIO *b, long size); 22 long BIO_set_buffer_size(BIO *b, long size); 23 long BIO_set_buffer_read_data(BIO *b, void *buf, long num); 24 25=head1 DESCRIPTION 26 27BIO_f_buffer() returns the buffering BIO method. 28 29Data written to a buffering BIO is buffered and periodically written 30to the next BIO in the chain. Data read from a buffering BIO comes from 31an internal buffer which is filled from the next BIO in the chain. 32Both BIO_gets() and BIO_puts() are supported. 33 34Calling BIO_reset() on a buffering BIO clears any buffered data. 35 36BIO_get_buffer_num_lines() returns the number of lines currently buffered. 37 38BIO_set_read_buffer_size(), BIO_set_write_buffer_size() and BIO_set_buffer_size() 39set the read, write or both read and write buffer sizes to B<size>. The initial 40buffer size is DEFAULT_BUFFER_SIZE, currently 4096. Any attempt to reduce the 41buffer size below DEFAULT_BUFFER_SIZE is ignored. Any buffered data is cleared 42when the buffer is resized. 43 44BIO_set_buffer_read_data() clears the read buffer and fills it with B<num> 45bytes of B<buf>. If B<num> is larger than the current buffer size the buffer 46is expanded. 47 48=head1 NOTES 49 50These functions, other than BIO_f_buffer(), are implemented as macros. 51 52Buffering BIOs implement BIO_read_ex() and BIO_gets() by using 53BIO_read_ex() operations on the next BIO in the chain and storing the 54result in an internal buffer, from which bytes are given back to the 55caller as appropriate for the call; a BIO_gets() is guaranteed to give 56the caller a whole line, and BIO_read_ex() is guaranteed to give the 57caller the number of bytes it asks for, unless there's an error or end 58of communication is reached in the next BIO. By prepending a 59buffering BIO to a chain it is therefore possible to provide 60BIO_gets() or exact size BIO_read_ex() functionality if the following 61BIOs do not support it. 62 63Do not add more than one BIO_f_buffer() to a BIO chain. The result of 64doing so will force a full read of the size of the internal buffer of 65the top BIO_f_buffer(), which is 4 KiB at a minimum. 66 67Data is only written to the next BIO in the chain when the write buffer fills 68or when BIO_flush() is called. It is therefore important to call BIO_flush() 69whenever any pending data should be written such as when removing a buffering 70BIO using BIO_pop(). BIO_flush() may need to be retried if the ultimate 71source/sink BIO is non blocking. 72 73=head1 RETURN VALUES 74 75BIO_f_buffer() returns the buffering BIO method. 76 77BIO_get_buffer_num_lines() returns the number of lines buffered (may be 0) or 78a negative value in case of errors. 79 80BIO_set_read_buffer_size(), BIO_set_write_buffer_size() and BIO_set_buffer_size() 81return 1 if the buffer was successfully resized or <=0 for failure. 82 83BIO_set_buffer_read_data() returns 1 if the data was set correctly or <=0 if 84there was an error. 85 86=head1 SEE ALSO 87 88L<bio(7)>, 89L<BIO_reset(3)>, 90L<BIO_flush(3)>, 91L<BIO_pop(3)>, 92L<BIO_ctrl(3)>. 93 94=head1 COPYRIGHT 95 96Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved. 97 98Licensed under the Apache License 2.0 (the "License"). You may not use 99this file except in compliance with the License. You can obtain a copy 100in the file LICENSE in the source distribution or at 101L<https://www.openssl.org/source/license.html>. 102 103=cut 104