I agree that being able to limit output size is useful and desirable, but
I'm not keen on copying the max_length/unconsumed_tail approach used by
zlib's decompressor class. It feels awkward to use, and it complicates
the implementation of the existing decompress() method, which is already
unwieldy enough.
As an alternative, I propose a thin wrapper around the underlying C API:
def decompress_into(self, src, dst, src_start=0, dst_start=0): ...
This would store decompressed data in a caller-provided bytearray, and
return a pair of integers indicating the end points of the consumed and
produced data in the respective buffers.
The implementation should be extremely simple - it does not need to do
any memory allocation or reference management.
I think it could also be useful for optimizing the implementation of
BZ2File and LZMAFile. I plan to write a prototype and run some benchmarks
some time in the next few weeks.
(Aside: if implemented for zlib, this could also be a nicer (I think)
solution for the problem raised in issue 5804.)