emogrifier path issue when base_path() and DRUPAL_ROOT contain same 'sitename' folder

I found out the reason I was having problems was related to the path not being correct in the url_to_realpath() function in url_to_path.inc
realpath(DRUPAL_ROOT . base_path() . $path); for me instead returns the sitename twice

'Users/username/Sites/sitename/sitename/sites/all/themes/mytheme/css/mytheme.css'

DRUPAL_ROOT : /Users/username/Sites/sitename
basepath() : /sitename/
$path : sites/all/themes/mytheme/css/mytheme.css

Is there something that could work in this case where Drupal has defined my DRUPAL_ROOT and basepath() and both contain the same folder? I just did a basic drush drupal install of this site, no symlinks or anything, so I suspect other people may encounter this

thx
-wil
ps changing title

I'm not a php expert but this is how I solved this, let me know if its at least possible to do some error checking on this function. Here's a start.

function url_to_realpath($url) {
  $path = url_to_path($url);
  if ($path) {
	$realpath = DRUPAL_ROOT . base_path();
	if ($match = preg_replace("/\b([\w\/]+)(\\1)+/i", "$1", $realpath)) { 
		drupal_set_message(t('Your DRUPAL_ROOT and base_path() for Emogrifier module contain duplicate directories. <br /> 
		The paths to your CSS stylesheets for Emogrifier were therefore set to @match/ and not @realpath. <br />
		See: url_to_path.inc in Emogrifier module (line 128)', array('@match' => realpath($match), '@realpath' => $realpath, )), $type = 'warning', $repeat = FALSE);
		return realpath($match . $path);
		}
	else return realpath($realpath . $path);
  }
  return FALSE;
}

thanks for taking a look. above doesn't work on my localhost but does on live site
below works on both:

    return realpath($_SERVER['DOCUMENT_ROOT'] . base_path() . $path);

i never had any problem with the module not working on a live site.

just to be clear, drupal is set up like this on my localhost http://localhost/drupal

1. base_path() returns /drupal/
2. DRUPAL_ROOT returns /Users/username/Sites/drupal
3. $_SERVER['DOCUMENT_ROOT'] returns /Users/username/Sites

on live site

1. base_path() returns /
2. DRUPAL_ROOT returns /home/username/drupal
3. $_SERVER['DOCUMENT_ROOT'] returns /home/username/drupal

sidenote: nothing was done out of the norm for this drupal install on my localhost
RewriteBase not on in .htaccess and no base_url declaration in settings.php

I can confirm it works on both my localhost and a live site. Thanks a lot. It was also a helpful exercise for me. I didn't test it on a multi-site set up which would be also important to check that DRUPAL_ROOT returns something like /home/username/drupal/sites/yoursitename and not just /home/username/drupal