I may have had my terminology wrong so sorry if that caused any confusion. But my example of the output files was correct in what I wanted to unzip/extract.
I was wanting to extract "Split" files, not "Spanned".
In my case I have 1 very large file that I is split into multiple volumes. Each volume being the same number of bytes. This can be done in 7zip by choosing "split to volumes, bytes:" when using "Add to Archive".
So if myfile is 22MB file and I split by 10MB then you get the following files all in the same directory.
myfile.zip.001 - 10MB
myfile.zip.002 - 10MB
myfile.zip.003 - 2MB
These are "Split".
The reason I thought this might be the same as Spanning is because I thought that it actually was the same, expect that spanning is used when the files are on different archive devices. IE split is in the same folder, spanned is across multiple DVDs.
In any case it looks like the C++ SDKs can't handle extracting these, which is what I was wanting to find out. So I will just do this myself.
Note that I haven't used the C++ SDK to create a spanned file either. Since I have no need to. I want to extract them, not create them. So I have no idea what setting the "SetSpanning" flag actually does. But if it did indeed split them into different volumes of a fixed byte size, and put then into the same output folder, then I assumed there would be a feature also in the SDK to read these back and extract them. Otherwise what is the point of C4D being able to create them in the first place?
@zipit You mentioned that splitting would create a dedicated *.zip file. This is definitely NOT the case with 7zip. The files all start as *.zip.001, *.zip.002, *.zip.003 etc... there is no single *.zip file. So this is probably a non standard feature of 7zip itself.