## BufferedReader.peek() ##
See <https://bugs.python.org/issue5811#msg233750>, but basically my concern is that the documentation says “the number of bytes returned may be less or more than requested”, without any mention of EOF or other conditions.

## Buffer sizing ##
In the code review, Nikolaus raised the idea of allowing a custom “buffer_size” parameter for the BufferedReader. I think this would need a bit of consideration about how it should work:

1. Should it be a direct wrapper around BufferedReader(buffer_size=...)?
2. Should it also support an unbuffered reader mode like open(buffering=0), socket.makefile(buffering=0), and subprocess.Popen(bufsize=0)?
3. Should there be any consideration for buffering in write mode (mirroring the equivalent open(), etc parameters)?

## Common raw decompression stream class ##
Having a common base class mapping the generic decompressor object API to the RawIOBase API is a good thing. I will try to make one in my next patch iteration. In the mean time, here are a couple of issues to consider:

* What module should it reside in? Perhaps “gzip”, because it is the most commonly-used of the three decompressors? Perhaps “io”, being the most relevant common dependency? Or a brand new internal module?!
* The zlib.decompressobj() API is slightly different, since it has the “unconsumed_tail” attribute and flush() methods, and decompress(max_length=0) does not mean return zero bytes (Issue 23200).

In Issue 23528, Nikolaus also pointed out that “GzipFile would need to additionally overwrite read() and write() in order to handle the CRC and gzip header.”