Convert hexadecimal to decimal

[confused via Digitalmars-d]

hi team!

I'm using this swift piece of code to seek out the Option 26 DHCP 
is deploying and output to the screen: 
https://github.com/CyberShadow/dhcptest/blob/master/dhcptest.d
(props for code CyberShadow).

When I get the value it says 0578. I've used an online converter 
to establish this is 1400 (which is what MTU value my dhcp server 
issues).

ideally what I want to do is have that converted from hexadecimal 
to decimal in the code, but as quite the noob, I cant figure it 
out.

any tips?