IP to world region

Is there an easy way to detect user region using IP address? I'd assume that each region will have a specific IPv4 range assigned.

• I don't want to rely on any 3rd party service (except initial data import)
• Precision does not need to be 100%, but should be reasonably high (at least ~80%)
• I only want to guess users region (Europe, Asia, Africa, ...). No need for city/country.