'Common code for GET and HEAD commands.
This sends the response code and MIME headers.
Return value is either a file object (which has to be copied
to the outputfile by the caller unless the command was HEAD,
and must be closed by the caller under all circumstances), or
None, in which case the caller has nothing further to do.'

def send_head(self):

    path = self.translate_path(self.path)
    f = None
    if os.path.isdir(path):
        if (not self.path.endswith('/')):
            self.send_response(301)
            self.send_header('Location', (self.path + '/'))
            self.end_headers()
            return None
        for index in ('index.html', 'index.htm'):
            index = os.path.join(path, index)
            if os.path.exists(index):
                path = index
                break
        else:
            return self.list_directory(path)
    ctype = self.guess_type(path)
    try:
        f = open(path, 'rb')
    except IOError:
        self.send_error(404, 'File    not    found')
        return None
    try:
        self.send_response(200)
        self.send_header('Content-type', ctype)
        fs = os.fstat(f.fileno())
        self.send_header('Content-Length', str(fs[6]))
        self.send_header('Last-Modified', self.date_time_string(fs.st_mtime))
        self.end_headers()
        return f
    except:
        f.close()
        raise
