BIO_F_BUFFER(3SSL)

💖 BIO_F_BUFFER — the buffering BIO, bestie edition 💖

okay so this is BIO_F_BUFFER(3SSL) from the OpenSSL crew, and it's literally the glow-up your BIO chain has been waiting for ✨

🌸 NAME 🌸

BIO_get_buffer_num_lines, BIO_set_read_buffer_size, BIO_set_write_buffer_size, BIO_set_buffer_size, BIO_set_buffer_read_data, BIO_f_buffer — the buffering BIO, periodt 💅

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🎀 SYNOPSIS 🎀

#include <openssl/bio.h>

const BIO_METHOD *BIO_f_buffer(void);

long BIO_get_buffer_num_lines(BIO *b);
long BIO_set_read_buffer_size(BIO *b, long size);
long BIO_set_write_buffer_size(BIO *b, long size);
long BIO_set_buffer_size(BIO *b, long size);
long BIO_set_buffer_read_data(BIO *b, void *buf, long num);

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🦋 DESCRIPTION 🦋

So like, BIO_f_buffer() hands you the buffering BIO method. That's the whole vibe. 🫶

Data you write to a buffering BIO gets buffered and then periodically written to the next BIO in the chain. Data you read from a buffering BIO comes from an internal buffer, and that buffer gets filled from the next BIO in the chain. Both BIO_gets() and BIO_puts() are supported, no cap.

Calling BIO_reset() on a buffering BIO clears out any buffered data. bye felicia 👋

BIO_get_buffer_num_lines() tells you how many lines are currently buffered.

BIO_set_read_buffer_size(), BIO_set_write_buffer_size() and BIO_set_buffer_size() set the read, write, or both read and write buffer sizes to size. The initial buffer size is DEFAULT_BUFFER_SIZE, currently 4096. Here's the tea tho — any attempt to reduce the buffer size below DEFAULT_BUFFER_SIZE is just ignored, like it simply does not hear you. And any buffered data is cleared when the buffer is resized, so don't be surprised ok.

BIO_set_buffer_read_data() clears the read buffer and fills it with num bytes of buf. If num is larger than the current buffer size, the buffer gets expanded. it's giving growth mindset 💅

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✨ NOTES ✨

These functions — all of them except BIO_f_buffer() — are implemented as macros. iykyk.

Buffering BIOs implement BIO_read_ex() and BIO_gets() by using BIO_read_ex() operations on the next BIO in the chain and storing the result in an internal buffer, from which bytes are given back to the caller as appropriate for the call. A BIO_gets() is guaranteed to give the caller a whole line, and BIO_read_ex() is guaranteed to give the caller the number of bytes it asks for — unless there's an error or end of communication is reached in the next BIO. So by prepending a buffering BIO to a chain, you can literally provide BIO_gets() or exact-size BIO_read_ex() functionality even if the following BIOs don't support it. main character energy fr fr 👑

🚨 bestie listen — do NOT add more than one BIO_f_buffer() to a BIO chain. The result of doing so will force a full read of the size of the internal buffer of the top BIO_f_buffer(), which is 4 KiB at a minimum. that's the drama we're avoiding 🙈

Data is only written to the next BIO in the chain when the write buffer fills or when BIO_flush() is called. So it is important to call BIO_flush() whenever any pending data should be written — like when you're removing a buffering BIO using BIO_pop(). And heads up: BIO_flush() may need to be retried if the ultimate source/sink BIO is non blocking. annoying but true 💀

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🌈 RETURN VALUES 🌈

• BIO_f_buffer() returns the buffering BIO method. iconic, as always.
• BIO_get_buffer_num_lines() returns the number of lines buffered (may be 0) or a negative value in case of errors.
• BIO_set_read_buffer_size(), BIO_set_write_buffer_size() and BIO_set_buffer_size() return 1 if the buffer was successfully resized, or <=0 for failure. 😭
• BIO_set_buffer_read_data() returns 1 if the data was set correctly, or <=0 if there was an error.

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💜 SEE ALSO 💜

bio(7), BIO_reset(3), BIO_flush(3), BIO_pop(3), BIO_ctrl(3). go read them, they're all part of the lore 📚

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👑 COPYRIGHT 👑

Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

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and that's the whole page babe 🎀 this was version 4.0.3, dated 2026-09-29, straight from the OpenSSL girlies — slay, stay buffered, and always flush before you pop 💖✨🌸