[issue5804] Add an 'offset' argument to zlib.decompress

[Kristján Valur Jónsson]

Kristján Valur Jónsson <kristjan at ccpgames.com> added the comment:

decompressobj is indeed "enough".  But if you are doing a lot of this (decompressing chunks), then using the unused_data, as it is, involves a lot of copying.
If there were a "unused_data_pos" or some equivalent, then it would be possible to continue decommpressing with buffer(olddata, unused_data_pos), without copying the source data.

The point of the "offset" keyword argument was to have a way to get this end position also without having an explicit decompressobj.

I agree that having the result type change to a tuple is not good.

So, a suggestion:
1) Add the unused_data_pos to the decompressobj.
2) (opotional) Add the automatic retrieval of this with a decompress_ex method, for convenience, making it usable without creating a decompressobj
3) (optional) Add the "offset" kw argument to decompress and (decompress_ex) making the creation of a temporary buffer() object unnecessary.

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue5804>
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