Replace interior Reader without resetting decompress data

[jnbooth]

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If I'm parsing a continuous encoded stream that is (unfortunately) divided up across several successive inputs, my only option appears to be using the Decompress object directly, which is a huge hassle without access to the zio:: functions.

It seems like it would be easy to create a "replace" method identical to the various "reset" methods, but with the reset_decoder_data(self); call removed. That way, I could switch out one Read object for the next while preserving the stream state.

[Gelbpunkt]

I would love this exact same feature but for ZlibEncoder - right now I can't reuse a ZlibEncoder object, but using Compress directly (https://gist.github.com/Gelbpunkt/44a6fb4cfe15f15e4c3757416b7021b1) doesn't work when I reuse the object. It does work fine when using reset on the Compress object before decompressing, but that seems to not preserve encoding parameters. Zlib gives invalid stored block lengths when using the same decoder (in python) to decode multiple payloads that were created by encoding and then resetting the Compress object.

[Byron]

I am probably not following on some intricacies of the problem, but wonder if it's possible to create a custom Write/Read that is Clone and uses shared ownership internally. That way it would be possible to keep a handle to it after passing it to types in this crate, and use interior mutability to swap out any state as you see fit.

I'd find that, in theory, more suitable as first step towards solving this particular problem as it's much less involved. Of course, it also delegates the hard parts of managing the internal decompressor state correctly which certainly wouldn't be trivial, but should be possible.