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audit pass on waker + generators

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cfsamson
2020-04-06 15:20:02 +02:00
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book/2_waker_context.html
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@@ -153,9 +153,9 @@
<blockquote>
<p><strong>Overview:</strong></p>
<ul>
<li>Understanding how the Waker object is constructed</li>
<li>Learning how the runtime know when a leaf-future can resume</li>
<li>Learning the basics of dynamic dispatch and trait objects</li>
<li>Understand how the Waker object is constructed</li>
<li>Learn how the runtime know when a leaf-future can resume</li>
<li>Learn the basics of dynamic dispatch and trait objects</li>
</ul>
<p>The <code>Waker</code> type is described as part of <a href="https://github.com/rust-lang/rfcs/blob/master/text/2592-futures.md#waking-up">RFC#2592</a>.</p>
</blockquote>
@@ -174,7 +174,7 @@ recommend <a href="https://boats.gitlab.io/blog/post/wakers-i/">Withoutboats art
</blockquote>
<h2><a class="header" href="#the-context-type" id="the-context-type">The Context type</a></h2>
<p>As the docs state as of now this type only wrapps a <code>Waker</code>, but it gives some
flexibility for future evolutions of the API in Rust. The context can hold
flexibility for future evolutions of the API in Rust. The context can for example hold
task-local storage and provide space for debugging hooks in later iterations.</p>
<h2><a class="header" href="#understanding-the-waker" id="understanding-the-waker">Understanding the <code>Waker</code></a></h2>
<p>One of the most confusing things we encounter when implementing our own <code>Futures</code>
@@ -230,11 +230,6 @@ except that it implements the methods defined by our trait. To accomplish this
we use <em>dynamic dispatch</em>.</p>
<p>Let's explain this in code instead of words by implementing our own trait
object from these parts:</p>
<blockquote>
<p>This is an example of <em>editable</em> code. You can change everything in the example
and try to run it. If you want to go back, press the undo symbol. Keep an eye
out for these as we go forward. Many examples will be editable.</p>
</blockquote>
<pre><pre class="playpen"><code class="language-rust">// A reference to a trait object is a fat pointer: (data_ptr, vtable_ptr)
trait Test {
fn add(&amp;self) -&gt; i32;
@@ -294,11 +289,10 @@ fn main() {
println!(&quot;Mul: 3 * 2 = {}&quot;, test.mul());
}
</code></pre></pre>
<p>Now that you know this you also know why how we implement the <code>Waker</code> type
in Rust.</p>
<p>Later on, when we implement our own <code>Waker</code> we'll actually set up a <code>vtable</code>
like we do here to and knowing why we do that and how it works will make this
much less mysterious.</p>
like we do here. The way we create it is slightly different, but now that you know
how regular trait objects work you will probably recognize what we're doing which
makes it much less mysterious.</p>
<h2><a class="header" href="#bonus-section" id="bonus-section">Bonus section</a></h2>
<p>You might wonder why the <code>Waker</code> was implemented like this and not just as a
normal trait?</p>