I am working on a proof of concept of a simple key value store service
using lmdb as the back end.
I am using sendfile to avoid an extra copy.
I accomplished this by creating function to extract get the mmap ptr from
the env so I can calculate the offset of data.
I figured that function might be useful to the bigger community.
If it does not fit in the bigger vision of lmdb it is fine not to include
You will find the diff attached.