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<ol class="chapter"><li class="affix"><a href="introduction.html">Introduction</a></li><li><a href="0_background_information.html"><strong aria-hidden="true">1.</strong> Background information</a></li><li><a href="1_futures_in_rust.html"><strong aria-hidden="true">2.</strong> Futures in Rust</a></li><li><a href="2_waker_context.html"><strong aria-hidden="true">3.</strong> Waker and Context</a></li><li><a href="3_generators_async_await.html"><strong aria-hidden="true">4.</strong> Generators and async/await</a></li><li><a href="4_pin.html"><strong aria-hidden="true">5.</strong> Pin</a></li><li><a href="6_future_example.html"><strong aria-hidden="true">6.</strong> Implementing Futures</a></li><li><a href="8_finished_example.html"><strong aria-hidden="true">7.</strong> Finished example (editable)</a></li><li class="affix"><a href="conclusion.html" class="active">Conclusion and exercises</a></li></ol>
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<h1 class="menu-title">Futures Explained in 200 Lines of Rust</h1>
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<h1><a class="header" href="#conclusion-and-exercises" id="conclusion-and-exercises">Conclusion and exercises</a></h1>
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<p>Congratulations. Good job! If you got this far you must have stayed with me
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all the way. I hope you enjoyed the ride!</p>
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<p>Remember that you call always leave feedback, suggest improvements or ask questions
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in the <a href="https://github.com/cfsamson/books-futures-explained/issues">issue_tracker</a> for this book.
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I'll try my best to respond to each one of them.</p>
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<p>I'll leave you with some suggestions for exercises if you want to explore a little further below.</p>
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<p>Until next time!</p>
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<h2><a class="header" href="#reader-exercises" id="reader-exercises">Reader exercises</a></h2>
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<p>So our implementation has taken some obvious shortcuts and could use some improvement.
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Actually digging into the code and try things yourself is a good way to learn. Here are
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some good exercises if you want to explore more:</p>
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<h3><a class="header" href="#avoid-threadpark" id="avoid-threadpark">Avoid <code>thread::park</code></a></h3>
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<p>The big problem using <code>Thread::park</code> and <code>Thread::unpark</code> is that the user can access these
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same methods from their own code. Try to use another method to suspend our thread and wake
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it up again on our command. Some hints:</p>
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<ul>
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<li>Check out <code>CondVars</code>, here are two sources <a href="https://en.wikipedia.org/wiki/Monitor_(synchronization)#Condition_variables">Wikipedia</a> and the
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docs for <a href="https://doc.rust-lang.org/stable/std/sync/struct.Condvar.html"><code>CondVar</code></a></li>
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<li>Take a look at crates that help you with this exact problem like <a href="https://github.com/crossbeam-rs/crossbeam">Crossbeam </a>(specifically the <a href="https://docs.rs/crossbeam/0.7.3/crossbeam/sync/struct.Parker.html"><code>Parker</code></a>)</li>
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</ul>
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<h3><a class="header" href="#avoid-wrapping-the-whole-reactor-in-a-mutex-and-pass-it-around" id="avoid-wrapping-the-whole-reactor-in-a-mutex-and-pass-it-around">Avoid wrapping the whole <code>Reactor</code> in a mutex and pass it around</a></h3>
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<p>First of all, protecting the whole <code>Reactor</code> and passing it around is overkill. We're only
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interested in synchronizing some parts of the information it contains. Try to refactor that
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out and only synchronize access to what's really needed.</p>
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<p>I'd encourage you to have a look at how <a href="https://github.com/async-rs/async-std/blob/master/src/net/driver/mod.rs">the async_std driver is implemented</a>
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and <a href="https://github.com/tokio-rs/tokio/blob/master/tokio/src/runtime/basic_scheduler.rs">how tokios scheduler is implemented</a> to get some inspiration.</p>
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<ul>
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<li>Do you want to pass around a reference to this information using an <code>Arc</code>?</li>
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<li>Do you want to make a global <code>Reactor</code> so it can be accessed from anywhere?</li>
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</ul>
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<h3><a class="header" href="#building-a-better-exectuor" id="building-a-better-exectuor">Building a better exectuor</a></h3>
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<p>Right now, we can only run one and one future. Most runtimes has a <code>spawn</code>
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function which let's you start off a future and <code>await</code> it later so you
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can run multiple futures concurrently.</p>
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<p>As I suggested in the start of this book, visiting <a href="https://stjepang.github.io/2020/01/31/build-your-own-executor.html">@stjepan'sblog series about implementing your own executors</a>
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is the place I would start and take it from there.</p>
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<h2><a class="header" href="#further-reading" id="further-reading">Further reading</a></h2>
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<p>There are many great resources. In addition to the RFCs and articles I've already
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linked to in the book, here are some of my suggestions:</p>
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<p><a href="https://rust-lang.github.io/async-book/01_getting_started/01_chapter.html">The official Asyc book</a></p>
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<p><a href="https://book.async.rs/">The async_std book</a></p>
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<p><a href="https://aturon.github.io/blog/2016/09/07/futures-design/">Aron Turon: Designing futures for Rust</a></p>
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<p><a href="https://www.infoq.com/presentations/rust-2019/">Steve Klabnik's presentation: Rust's journey to Async/Await</a></p>
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<p><a href="https://tokio.rs/blog/2019-10-scheduler/">The Tokio Blog</a></p>
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<p><a href="https://stjepang.github.io/">Stjepan's blog with a series where he implements an Executor</a></p>
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<p><a href="https://youtu.be/DkMwYxfSYNQ">Jon Gjengset's video on The Why, What and How of Pinning in Rust</a></p>
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<p><a href="https://boats.gitlab.io/blog/post/2018-01-25-async-i-self-referential-structs/">Withoutboats blog series about async/await</a></p>
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