[Feature Request]: nice api for ArchiveExtractCallback/ISequentialOutStream

[RScherzer]

Feature description

Would be great if there would be an easy, clean interface in 4.x for adding a callback which is able to work on the currently decompressed block of data, so you can e.g. calculate the sha1 hash value of a file while it is being decompressed blockwise to memory.
In 7z sdk theory this is an archive Extract call in test mode with ArchiveExtractCallback + ISequentialOutStream specified which inits the hash calculation, doing the hash update during the streams write calls and finalizing the hash when the extractcallback does its SetOperationResult.

Additional context

No response

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[rikyoz]

Hi!
Sorry for the late reply!

Would be great if there would be an easy, clean interface in 4.x for adding a callback which is able to work on the currently decompressed block of data, so you can e.g. calculate the sha1 hash value of a file while it is being decompressed blockwise to memory.

I think it would be a great feature indeed, I will definitely add it to the library.
Thanks for the suggestion!

In 7z sdk theory this is an archive Extract call in test mode with ArchiveExtractCallback + ISequentialOutStream specified which inits the hash calculation, doing the hash update during the streams write calls and finalizing the hash when the extractcallback does its SetOperationResult.

Yeah, I need to find out the best API for providing the feature.
I have some ideas which I need to test out.

I consider the v4.0 feature complete, so I'll probably add this feature to the next v4.1.

[RScherzer]

I've implemented it myself already (not worth or already nice enough for a pull request).

Generally I've added 2 callbacks to bitAbstractArchiveHandler

• one which hooks into ExtractCallback::GetStream and allows the callback to set its own outStream instead of using the default implementation
• one which is called in SetOperationResult
• additionally I've added the single test feature from my other feature request (which is pretty straight forward adding another testArc and test in bitinputarchive.cpp)

So when I want to calculate a sha1 from a single compressed file, I set up the 2 callbacks.
The GetStream one setups a new ISequentialOutStream which calls the sha1 update in its write method and the sha1 finalize is called in the SetOperationResult callback.
To trigger the callbacks I do a single entry test operation after setting up the callbacks.

As I said...not yet in an api-nice way, but functional ;-)

Having the stream-replace callback I will be able to solve my "give the decompressed files different names", too.

Thanks for your support!