const PRUnichar* chunk_end = c + chunk_size;
const PRUnichar* fragmentEnd = c + fragmentLength;
IsASCII( const nsAReadableString& aString )  {    static const PRUnichar NOT_ASCII = PRUnichar(~0x007F);    // Don't want to use |copy_string| for this task, since we can stop at the first non-ASCII character    typedef nsAReadableString::const_iterator iterator;    iterator iter = aString.BeginReading();    iterator done_reading = aString.EndReading();      // for each chunk of |aString|...    while ( iter != done_reading )      {        iterator::difference_type chunk_size = iter.size_forward();        const PRUnichar* c = iter.get();        const PRUnichar* chunk_end = c + chunk_size;          // for each character in this chunk...        while ( c < chunk_end )          if ( *c++ & NOT_ASCII )            return PR_FALSE;        iter += chunk_size;      }    return PR_TRUE;  }