ConvertVAtoFileOffsetEx 
ConvertVAtoFileOffsetEx 

* now returns 0 on error (and not INVALID_VALUE  => -1)
* implementation for ReturnType 

In short I just copied that from:
https://github.com/x64dbg/GleeBug/blob/c5aed9fcccb9f2161af86cfefe0ef5006e913fc9/StaticEngine/Emulator.h#L507
x64dbg/GleeBug,x64dbg/GleeBug