Add fields for total compressed and uncompressed sizes of archive

[gerchicov-bp]

It enough complex code but you made it private. It is even not separated into the method

[abbeycode]

I don't understand exactly what you're asking for. You can use the following code (copied from -extractFilesTo:overwrite:progress:error:) to get an archive's total uncompressed size:

NSError *listError = nil;
NSArray *fileInfo = [self listFileInfo:&listError];
NSNumber *totalSize = [fileInfo valueForKeyPath:@"@sum.uncompressedSize"];

Are you suggesting I make a property of URKArchive with that code?

[gerchicov-bp]

Yes, it is better to make this code as a property.
I was confused a little when you get total size and in the same time you get uncompressedSize via 2 different ways. Now I understand that the first way is to get the whole size at once and the second one is to calculate the common size of the unpacked files

[abbeycode]

How are you currently getting the total (compressed) size? I don't remember there being a call for that, either.

[gerchicov-bp]

I created a derived class and use it. So now my code looks almost exactly as your one above + some checks from your file

[abbeycode]

This has been merged into master and will be included in the next release. Let me know if it works for you!