What is best way to convert a file URL to a BOOST filesystem path in C++?

I'm writing a library that has filenames as inputs. One feature that I'm trying to include is to allow the user to pass in file URLs or file paths, because sometimes the input is generated from parsing XML, 开发者_JS百科other time it's not. I'm using the boost filesystem to manipulate the path, and is wondering what is the best way to convert a file URL to a boost filesystem path object.