Get Currently Logged In User's Id

How can I retrieve the currently logged in user's ID from within a Module?

Code:

---


class SomeModule extends Module
{
    protected $strTemplate = 'mod_someTemplate';

    public function generate()
    {
        return parent::generate();
    }

    protected function compile()
    {
        $user_id = /* Get the currently logged in user's ID here! */;
    }
}

---

[code=php:2irft68s]<span class="syntaxdefault">
$this</span><span class="syntaxkeyword">-></span><span class="syntaxdefault">import</span><span class="syntaxkeyword">(</span><span class="syntaxstring">'FrontendUser'</span><span class="syntaxkeyword">,*</span><span class="syntaxstring">'User'</span><span class="syntaxkeyword">);

</span><span class="syntaxdefault">$user_id*</span><span class="syntaxkeyword">=*</span><span class="syntaxdefault">$this</span><span class="syntaxkeyword">-></span><span class="syntaxdefault">User</span><span class="syntaxkeyword">-></span><span class="syntaxdefault">id</span><span class="syntaxkeyword">;
*</span><span class="syntaxdefault"></span>[/code:2irft68s]