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</pre><pre class="rust"><code><span class="kw">use </span><span class="kw">super</span>::arc_wake::ArcWake;
<span class="kw">use </span><span class="kw">super</span>::waker::waker_vtable;
<span class="kw">use </span>alloc::sync::Arc;
<span class="kw">use </span>core::marker::PhantomData;
<span class="kw">use </span>core::mem::ManuallyDrop;
<span class="kw">use </span>core::ops::Deref;
<span class="kw">use </span>core::task::{RawWaker, Waker};
<span class="doccomment">/// A [`Waker`] that is only valid for a given lifetime.
///
/// Note: this type implements [`Deref&lt;Target = Waker&gt;`](std::ops::Deref),
/// so it can be used to get a `&amp;Waker`.
</span><span class="attribute">#[derive(Debug)]
</span><span class="kw">pub struct </span>WakerRef&lt;<span class="lifetime">&#39;a</span>&gt; {
waker: ManuallyDrop&lt;Waker&gt;,
_marker: PhantomData&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>()&gt;,
}
<span class="kw">impl</span>&lt;<span class="lifetime">&#39;a</span>&gt; WakerRef&lt;<span class="lifetime">&#39;a</span>&gt; {
<span class="doccomment">/// Create a new [`WakerRef`] from a [`Waker`] reference.
</span><span class="attribute">#[inline]
</span><span class="kw">pub fn </span>new(waker: <span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>Waker) -&gt; <span class="self">Self </span>{
<span class="comment">// copy the underlying (raw) waker without calling a clone,
// as we won&#39;t call Waker::drop either.
</span><span class="kw">let </span>waker = ManuallyDrop::new(<span class="kw">unsafe </span>{ core::ptr::read(waker) });
<span class="self">Self </span>{ waker, _marker: PhantomData }
}
<span class="doccomment">/// Create a new [`WakerRef`] from a [`Waker`] that must not be dropped.
///
/// Note: this if for rare cases where the caller created a [`Waker`] in
/// an unsafe way (that will be valid only for a lifetime to be determined
/// by the caller), and the [`Waker`] doesn&#39;t need to or must not be
/// destroyed.
</span><span class="attribute">#[inline]
</span><span class="kw">pub fn </span>new_unowned(waker: ManuallyDrop&lt;Waker&gt;) -&gt; <span class="self">Self </span>{
<span class="self">Self </span>{ waker, _marker: PhantomData }
}
}
<span class="kw">impl </span>Deref <span class="kw">for </span>WakerRef&lt;<span class="lifetime">&#39;_</span>&gt; {
<span class="kw">type </span>Target = Waker;
<span class="attribute">#[inline]
</span><span class="kw">fn </span>deref(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; <span class="kw-2">&amp;</span>Waker {
<span class="kw-2">&amp;</span><span class="self">self</span>.waker
}
}
<span class="doccomment">/// Creates a reference to a [`Waker`] from a reference to `Arc&lt;impl ArcWake&gt;`.
///
/// The resulting [`Waker`] will call
/// [`ArcWake.wake()`](ArcWake::wake) if awoken.
</span><span class="attribute">#[inline]
</span><span class="kw">pub fn </span>waker_ref&lt;W&gt;(wake: <span class="kw-2">&amp;</span>Arc&lt;W&gt;) -&gt; WakerRef&lt;<span class="lifetime">&#39;_</span>&gt;
<span class="kw">where
</span>W: ArcWake,
{
<span class="comment">// simply copy the pointer instead of using Arc::into_raw,
// as we don&#39;t actually keep a refcount by using ManuallyDrop.&lt;
</span><span class="kw">let </span>ptr = Arc::as_ptr(wake).cast::&lt;()&gt;();
<span class="kw">let </span>waker =
ManuallyDrop::new(<span class="kw">unsafe </span>{ Waker::from_raw(RawWaker::new(ptr, waker_vtable::&lt;W&gt;())) });
WakerRef::new_unowned(waker)
}
</code></pre></div>
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