I don't know to make an Engine to use within OpenSSL application

[Nacho Álvarez]

Hello

I know how to do an engine implementation that overwrite OpenSLL
functionality (like RSA sign and verify, ...) but I want to do an
implementation (dll) can be called from OpenSSL (through OpenSSl config
file).
How do I build this dll for OpenSSL? I don't know the structure of these
DLLs.

Thanks.