Getting my Database name in a C Extension

Hi,

I'm writing an extention (FDW), and I need, in my C code, the name of
my database ("contrib_regression_test" for example), and I've two
questions:

1) What is the easiest way to get that directly in C?

2) Is there a way to get this information in the SQL extension
installation/update scripts (like the @/extschema/@ substitution)?

Thanks,

Cedric