BIO_F_READBUFFER(3ossl)

📦
version 3.5.9 · 8 versions
, in fedora 43, fedora 44

💖 BIO_F_READBUFFER 💖

okay bestie, gather round — this is the BIO_F_READBUFFER page from the OpenSSL manuals, and it's giving "buffering but make it seekable". Let's get into it 🦋

✨ NAME ✨

BIO_f_readbuffer — a read only buffering BIO that supports BIO_tell() and BIO_seek() 🎀

✨ SYNOPSIS ✨

#include <openssl/bio.h>

const BIO_METHOD *BIO_f_readbuffer(void);

✨ DESCRIPTION ✨

BIO_f_readbuffer() returns the read buffering BIO method. That's the whole vibe 💅

This BIO filter can be inserted on top of BIO's that do not support BIO_tell() or BIO_seek() — like, for example, a file BIO that uses stdin. iykyk 🫶

Data read from a read buffering BIO comes from an internal buffer, and that buffer gets filled from the next BIO in the chain. Chain energy, literally ✨

BIO_gets() is supported for read buffering BIOs. Slay. But writing data to a read buffering BIO is not supported — it's read only, bestie, respect the boundary 😭

Also lowkey important: calling BIO_reset() on a read buffering BIO does not clear any buffered data. The buffer stays. It's committed 💀

✨ NOTES ✨

Read buffering BIOs implement BIO_read_ex() by using BIO_read_ex() operations on the next BIO (e.g. a file 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. Efficient? Yes. Iconic? Also yes. 🧚

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 basically: you get what you asked for, or something went sideways 🙈

The internal buffer can grow to cache the entire contents of the next BIO in the chain. Main character buffer energy. 👑

BIO_seek() uses the internal buffer, so it can only seek into data that is already read. No time travel, no seeking into the future, periodt 💅

✨ RETURN VALUES ✨

BIO_f_readbuffer() returns the read buffering BIO method. Same as above, fr fr 🌸

✨ SEE ALSO ✨

Copyright 2021 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. 🌈

Friendly reminder bestie: read the license, it's not a vibe-killer, it's just the rules 🎀

And that's the whole page!! This was version 3.5.9, dated 2026-09-29, from the BIO_F_READBUFFER(3ossl) manual. Go forth and buffer, you absolute icon 🦋✨💖

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