fopen a file that resides in flash

Using the Nios IDE, I flashed a bitmap into memory.

The problem I am having is that I want to use Altera file functions, like fopen, fclose on the file that resides in flash.

Is there a way to force fopen to look at a memory address rather than a const char*? fopen seems to lookup an index of names based on the passed in filename.. but I don't see where the list it's comparing against resides. How can I fake it out so that it just uses a fixed flash address as the source?