core foundation file manager

It's fun to reduce one problem to an already-solved problem.
I was working to remove all uses of the NSFileManager and replace them with faster CF file manager calls. I have one last function to fix, and even that is done (sans debugging) except that it relies on being able to determine if a file exists at a path held in a CFStringRef. I have a function

bool MyClass::fileExistsAtPath(NSString *filePath)
{
  return [[NSFileManager defaultManager] fileExistsAtPath:filePath];
}

but I want it to be

bool MyClass::fileExistsAtPath(CFStringRef path)
{
  return ???;
}

I have been searching the documentation, and I thought I could use a CFURL for this, but so far, I don't see any API that will tell me whether the url is valid.