adding save/load functionality

[lemire]

Alternative to #49

[Giulio2002]

wait but this actually won't work with mmap anyways - mmap is also part of our usecase. is there any interest in that or should I just make a fork?

[lemire]

@Giulio2002 Supporting memory file mapping on big endian platforms based on files created on a little endian system seems quite niche.

Can you elaborate on your application?

Is this a real issue you are encountering? If so, please elaborate on your business needs so that I understand.

[Giulio2002]

We handle a distributed database for the Ethereum blockchain. we have some data which we generate and users can use our OSS tool to sync this data. we sync the data through bittorent (files we distribute and seed) and currently we use bloom filters for our existence filters (and looking to switch). However, if a user is using a BE CPU and we generate with a LE CPU and use Fuse filters, we have an issue. We use MMAP because some of these filters are huge (as in > 2.2B entries). and bloom filters already take >30GB in total so cannot stay in RAM (We are mandated for 64GB Ram requirement in total).

If it's too niche which talking out loud, it probably is, I will make my own fork no issue.

[lemire]

You can do this without changing the xorfilter library.

[Giulio2002]

well not really, I suppose you could by changing exposed FingerPrints but still it is far from optimal. changing the lib is more self-contained. if its not in the lib interest, I completely understand.

[lemire]

I think that the proper way is to flip the bytes when transmitting the binary data to a big endian system. If you have enough sophistication to do memory file mapping on mainframe computers using data generated from regular computers, then that’s easy.