mirror of
https://github.com/google/comprehensive-rust.git
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Add the description of the chat-app exercise (#641)
* Adds a description of the async chat exercise * Simplifies the use of Error in chat-async * Links the solution to the async chat exercise * Removes the elevator exercise
This commit is contained in:
rbehjati
GitHub
parent
8406697449
commit
83663daaa2
16
Cargo.lock
generated
16
Cargo.lock
generated
@ -187,7 +187,6 @@ version = "0.1.0"
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dependencies = [
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"futures-util",
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"http",
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"thiserror",
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"tokio",
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"tokio-websockets",
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]
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@ -1996,6 +1995,15 @@ version = "1.1.0"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "43b2853a4d09f215c24cc5489c992ce46052d359b5109343cbafbf26bc62f8a3"
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[[package]]
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name = "signal-hook-registry"
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version = "1.4.1"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "d8229b473baa5980ac72ef434c4415e70c4b5e71b423043adb4ba059f89c99a1"
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dependencies = [
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"libc",
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]
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[[package]]
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name = "siphasher"
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version = "0.3.10"
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@ -2185,7 +2193,9 @@ dependencies = [
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"libc",
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"mio",
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"num_cpus",
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"parking_lot",
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"pin-project-lite",
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"signal-hook-registry",
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"socket2",
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"tokio-macros",
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"windows-sys 0.48.0",
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@ -2251,9 +2261,9 @@ dependencies = [
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[[package]]
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name = "tokio-websockets"
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version = "0.3.0"
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version = "0.3.2"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "d009a9a2a71bd44791363f42ba2dd7d47bf49aa61f7c43eabcd29a285e75a865"
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checksum = "8d1df20f31f428a351ec353699a82aad49360090e8f6320ac0dacf5def4f1573"
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dependencies = [
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"base64 0.21.0",
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"bytes",
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@ -52,6 +52,7 @@ editable = true
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"exercises/day-4/link-checker.html" = "../concurrency/link-checker.html"
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"exercises/day-4/morning.html" = "../concurrency/morning.html"
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"exercises/day-4/solutions-morning.html" = "../concurrency/solutions-morning.html"
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"exercises/concurrency/elevator.html" = "chat-app.html"
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"generics/closures.html" = "../traits/closures.html"
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"generics/impl-trait.html" = "../traits/impl-trait.html"
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"generics/trait-bounds.html" = "../traits/trait-bounds.html"
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@ -292,7 +292,7 @@
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- [Async Traits](async/pitfalls/async-traits.md)
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- [Exercises](exercises/concurrency/afternoon.md)
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- [Dining Philosophers](exercises/concurrency/dining-philosophers-async.md)
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- [Elevator Operations](exercises/concurrency/elevator.md)
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- [Broadcast Chat Application](exercises/concurrency/chat-app.md)
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# Final Words
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@ -5,8 +5,8 @@ To practice your Async Rust skills, we have again two exercises for you:
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* Dining philosophers: we already saw this problem in the morning. This time
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you are going to implement it with Async Rust.
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* The Elevator Problem: this is a larger project that allows you experiment
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with more advanced Async Rust features and some of its pitfalls!
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* A Broadcast Chat Application: this is a larger project that allows you
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experiment with more advanced Async Rust features.
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<details>
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109
src/exercises/concurrency/chat-app.md
Normal file
109
src/exercises/concurrency/chat-app.md
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@ -0,0 +1,109 @@
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# Broadcast Chat Application
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In this exercise, we want to use our new knowledge to implement a broadcast
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chat application. We have a chat server that the clients connect to and publish
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their messages. The client reads user messages from the standard input, and
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sends them to the server. The chat server broadcasts each message that it
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receives to all the clients.
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For this, we use [a broadcast channel][1] on the server, and
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[`tokio_websockets`][2] for the communication between the client and the
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server.
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Create a new Cargo project and add the following dependencies:
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`Cargo.toml`:
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<!-- File Cargo.toml -->
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```toml
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{{#include chat-async/Cargo.toml}}
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```
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## The required APIs
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You are going to need the following functions from `tokio` and
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[`tokio_websockets`][2]. Spend a few minutes to familiarize yourself with the
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API.
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- [WebsocketStream::next()][3]: for asynchronously reading messages from a
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Websocket Stream.
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- [SinkExt::send()][4] implemented by `WebsocketStream`: for asynchronously
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sending messages on a Websocket Stream.
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- [BufReader::read_line()][5]: for asynchronously reading user messages
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from the standard input.
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- [Sender::subscribe()][6]: for subscribing to a broadcast channel.
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## Two binaries
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Normally in a Cargo project, you can have only one binary, and one
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`src/main.rs` file. In this project, we need two binaries. One for the client,
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and one for the server. You could potentially make them two separate Cargo
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projects, but we are going to put them in a single Cargo project with two
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binaries. For this to work, the client and the server code should go under
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`src/bin` (see the [documentation][7]).
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Copy the following server and client code into `src/bin/server.rs` and
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`src/bin/client.rs`, respectively. Your task is to complete these files as
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described below.
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`src/bin/server.rs`:
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<!-- File src/bin/server.rs -->
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```rust,compile_fail
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{{#include chat-async/src/bin/server.rs:setup}}
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{{#include chat-async/src/bin/server.rs:handle_connection}}
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// TODO: For a hint, see the description of the task below.
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{{#include chat-async/src/bin/server.rs:main}}
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```
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`src/bin/client.rs`:
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<!-- File src/bin/client.rs -->
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```rust,compile_fail
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{{#include chat-async/src/bin/client.rs:setup}}
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// TODO: For a hint, see the description of the task below.
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}
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```
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## Running the binaries
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Run the server with:
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```shell
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$ cargo run --bin server
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```
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and the client with:
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```shell
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$ cargo run --bin client
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```
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## Tasks
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* Implement the `handle_connection` function in `src/bin/server.rs`.
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* Hint: Use `tokio::select!` for concurrently performing two tasks in a
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continuous loop. One task receives messages from the client and broadcasts
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them. The other sends messages received by the server to the client.
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* Complete the main function in `src/bin/client.rs`.
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* Hint: As before, use `tokio::select!` in a continuous loop for concurrently
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performing two tasks: (1) reading user messages from standard input and
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sending them to the server, and (2) receiving messages from the server, and
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displaying them for the user.
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* Optional: Once you are done, change the code to broadcast messages to all
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clients, but the sender of the message.
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[1]: https://docs.rs/tokio/latest/tokio/sync/broadcast/fn.channel.html
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[2]: https://docs.rs/tokio-websockets/0.3.2/tokio_websockets/
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[3]: https://docs.rs/tokio-websockets/0.3.2/tokio_websockets/proto/struct.WebsocketStream.html#method.next
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[4]: https://docs.rs/futures-util/0.3.28/futures_util/sink/trait.SinkExt.html#method.send
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[5]: https://docs.rs/tokio/latest/tokio/io/trait.AsyncBufReadExt.html#method.read_line
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[6]: https://docs.rs/tokio/latest/tokio/sync/broadcast/struct.Sender.html#method.subscribe
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[7]: https://doc.rust-lang.org/cargo/reference/cargo-targets.html#binaries
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@ -6,6 +6,5 @@ edition = "2021"
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[dependencies]
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futures-util = "0.3.28"
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http = "0.2.9"
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thiserror = "1.0.40"
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tokio = { version = "1.28.1", features = ["net", "macros", "time", "rt", "rt-multi-thread", "io-std", "io-util"] }
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tokio-websockets = "0.3.0"
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tokio = { version = "1.28.1", features = ["full"] }
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tokio-websockets = "0.3.2"
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@ -1,3 +1,18 @@
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// Copyright 2023 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// ANCHOR: setup
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use futures_util::SinkExt;
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use http::Uri;
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use tokio::io::{AsyncBufReadExt, BufReader};
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@ -12,6 +27,8 @@ async fn main() -> Result<(), tokio_websockets::Error> {
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let stdin = tokio::io::stdin();
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let mut stdin = BufReader::new(stdin);
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// ANCHOR_END: setup
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// Continuous loop for concurrently sending and receiving messages.
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loop {
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let mut line = String::new();
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tokio::select! {
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@ -1,46 +1,42 @@
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// Copyright 2023 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// ANCHOR: setup
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use futures_util::sink::SinkExt;
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use std::error::Error;
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use std::net::SocketAddr;
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use thiserror::Error;
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use tokio::net::{TcpListener, TcpStream};
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use tokio::sync::broadcast::error::{RecvError, SendError};
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use tokio::sync::broadcast::{channel, Sender};
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use tokio_websockets::{Message, ServerBuilder, WebsocketStream};
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// ANCHOR_END: setup
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#[derive(Error, Debug)]
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enum ServerError {
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#[error("websocket error: {0}")]
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Websocket(String),
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#[error("io error: {0}")]
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IO(#[from] std::io::Error),
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#[error("broadcast channel SendError: {0}")]
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SendError(#[from] SendError<String>),
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#[error("broadcast channel RecvError: {0}")]
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RecvError(#[from] RecvError),
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}
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// tokio_websockets Error types do not implement std::error::Error, so we make do by just capturing
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// the debug format for the error.
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impl From<tokio_websockets::Error> for ServerError {
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fn from(err: tokio_websockets::Error) -> Self {
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ServerError::Websocket(format!("{:?}", err))
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}
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}
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impl From<tokio_websockets::proto::ProtocolError> for ServerError {
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fn from(err: tokio_websockets::proto::ProtocolError) -> Self {
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ServerError::Websocket(format!("{:?}", err))
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}
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}
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// ANCHOR: handle_connection
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async fn handle_connection(
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addr: SocketAddr,
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mut ws_stream: WebsocketStream<TcpStream>,
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bcast_tx: Sender<String>,
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) -> Result<(), ServerError> {
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) -> Result<(), Box<dyn Error + Send + Sync>> {
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// ANCHOR_END: handle_connection
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ws_stream
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.send(Message::text("Welcome to chat! Type a message".into()))
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.await?;
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let mut bcast_rx = bcast_tx.subscribe();
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// A continuous loop for concurrently performing two tasks: (1) receiving
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// messages from `ws_stream` and broadcasting them, and (2) receiving
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// messages on `bcast_rx` and sending them to the client.
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loop {
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tokio::select! {
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incoming = ws_stream.next() => {
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@ -59,10 +55,11 @@ async fn handle_connection(
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}
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}
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}
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// ANCHOR: main
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}
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#[tokio::main]
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async fn main() -> Result<(), ServerError> {
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async fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
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let (bcast_tx, _) = channel(16);
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let listener = TcpListener::bind("127.0.0.1:2000").await?;
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@ -80,3 +77,4 @@ async fn main() -> Result<(), ServerError> {
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});
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}
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}
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// ANCHOR_END: main
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@ -1,91 +0,0 @@
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# Elevator Operation
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Elevators seem simple. You press a button, doors open, you wait, and you're at
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the floor you requested. But implementing an elevator controller is surprisingly
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difficult! This exercise involves building a simple elevator control that
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operates in a simple simulator.
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The overall design of this elevator uses the actor pattern: you will implement a
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controller task that communicates with other components of the elevator system
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by sending and receiving messages.
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## Getting Started
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Download the [exercise template](../../comprehensive-rust-exercises.zip) and look in the `elevator`
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directory for the following files.
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`src/main.rs`:
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<!-- File src/main.rs -->
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```rust,compile_fail
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{{#include elevator/src/main.rs}}
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```
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`src/building.rs`:
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<!-- File src/building.rs -->
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```rust,compile_fail
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{{#include elevator/src/building.rs}}
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```
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`src/driver.rs`:
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<!-- File src/driver.rs -->
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```rust,compile_fail
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{{#include elevator/src/driver.rs}}
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```
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`src/controller.rs`:
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<!-- File src/controller.rs -->
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```rust,compile_fail
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{{#include elevator/src/controller.rs}}
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```
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`Cargo.toml` (you shouldn't need to change this):
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<!-- File Cargo.toml -->
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```toml
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{{#include elevator/Cargo.toml}}
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```
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Use `cargo run` to run the elevator simulation.
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## Exercises
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Begin by implementing a controller that can transport the passengers provided by
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the simple driver. There is only one elevator, and passengers always go from
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floor 0 to floor 2, one-by-one.
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Once you have this done, make the problem more complex. Suggested tasks:
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* Make the driver more complex, with passengers arriving at random floors with
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random destinations at random times.
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* Create a building with more than one elevator, and adjust the controller to
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handle this efficiently.
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* Add additional events and metadata to analyze your controller's efficiency.
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What is the distribution of wait time for passengers? Is the result fair?
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* Modify the building to support a maximum passenger capacity for each
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elevator, and modify the controller to take this information into account.
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* Update the driver to simulate business traffic, with lots of passengers going
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up from the ground floor at the same time, and those passengers returning to
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the ground floor some time later. Can your controller adjust to these
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circumstances?
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* Modify the building to support "destination dispatch", where passengers
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signal their destination floor in the elevator lobby, before boarding the
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elevator.
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* If you are taking the course with other students, trade controllers or
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drivers with another student to see how robust your design is.
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* Build a textual or graphical display of the elevators as they run.
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318
src/exercises/concurrency/elevator/Cargo.lock
generated
318
src/exercises/concurrency/elevator/Cargo.lock
generated
@ -1,318 +0,0 @@
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# This file is automatically @generated by Cargo.
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# It is not intended for manual editing.
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version = 3
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[[package]]
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name = "autocfg"
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[[package]]
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[[package]]
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name = "bytes"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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[[package]]
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name = "cfg-if"
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checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
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[[package]]
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name = "elevator"
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version = "0.1.0"
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dependencies = [
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"tokio",
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]
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[[package]]
|
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"libc",
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||||
]
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|
||||
[[package]]
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||||
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|
||||
"autocfg",
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"scopeguard",
|
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]
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|
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[[package]]
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|
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"cfg-if",
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|
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"libc",
|
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"log",
|
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"wasi",
|
||||
"windows-sys",
|
||||
]
|
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|
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[[package]]
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|
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"hermit-abi",
|
||||
"libc",
|
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]
|
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|
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[[package]]
|
||||
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||||
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|
||||
"lock_api",
|
||||
"parking_lot_core",
|
||||
]
|
||||
|
||||
[[package]]
|
||||
name = "parking_lot_core"
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||||
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|
||||
"cfg-if",
|
||||
"libc",
|
||||
"redox_syscall",
|
||||
"smallvec",
|
||||
"windows-sys",
|
||||
]
|
||||
|
||||
[[package]]
|
||||
name = "pin-project-lite"
|
||||
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||||
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||||
|
||||
[[package]]
|
||||
name = "proc-macro2"
|
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||||
dependencies = [
|
||||
"unicode-ident",
|
||||
]
|
||||
|
||||
[[package]]
|
||||
name = "quote"
|
||||
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|
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"proc-macro2",
|
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]
|
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|
||||
[[package]]
|
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name = "redox_syscall"
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||||
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|
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"bitflags",
|
||||
]
|
||||
|
||||
[[package]]
|
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name = "scopeguard"
|
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|
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[[package]]
|
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name = "signal-hook-registry"
|
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"libc",
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[[package]]
|
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name = "smallvec"
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[[package]]
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"libc",
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[[package]]
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name = "syn"
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"quote",
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]
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[[package]]
|
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name = "tokio"
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"autocfg",
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"bytes",
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"libc",
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"mio",
|
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"num_cpus",
|
||||
"parking_lot",
|
||||
"pin-project-lite",
|
||||
"signal-hook-registry",
|
||||
"socket2",
|
||||
"tokio-macros",
|
||||
"windows-sys",
|
||||
]
|
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|
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[[package]]
|
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name = "tokio-macros"
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"quote",
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"syn",
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]
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|
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[[package]]
|
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name = "unicode-ident"
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[[package]]
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"winapi-i686-pc-windows-gnu",
|
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"winapi-x86_64-pc-windows-gnu",
|
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]
|
||||
|
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[[package]]
|
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name = "winapi-i686-pc-windows-gnu"
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[[package]]
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dependencies = [
|
||||
"windows-targets",
|
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]
|
||||
|
||||
[[package]]
|
||||
name = "windows-targets"
|
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dependencies = [
|
||||
"windows_aarch64_gnullvm",
|
||||
"windows_aarch64_msvc",
|
||||
"windows_i686_gnu",
|
||||
"windows_i686_msvc",
|
||||
"windows_x86_64_gnu",
|
||||
"windows_x86_64_gnullvm",
|
||||
"windows_x86_64_msvc",
|
||||
]
|
||||
|
||||
[[package]]
|
||||
name = "windows_aarch64_gnullvm"
|
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||||
|
||||
[[package]]
|
||||
name = "windows_aarch64_msvc"
|
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|
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source = "registry+https://github.com/rust-lang/crates.io-index"
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||||
checksum = "e08e8864a60f06ef0d0ff4ba04124db8b0fb3be5776a5cd47641e942e58c4d43"
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||||
|
||||
[[package]]
|
||||
name = "windows_i686_gnu"
|
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|
||||
source = "registry+https://github.com/rust-lang/crates.io-index"
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||||
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|
||||
|
||||
[[package]]
|
||||
name = "windows_i686_msvc"
|
||||
version = "0.42.2"
|
||||
source = "registry+https://github.com/rust-lang/crates.io-index"
|
||||
checksum = "44d840b6ec649f480a41c8d80f9c65108b92d89345dd94027bfe06ac444d1060"
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||||
|
||||
[[package]]
|
||||
name = "windows_x86_64_gnu"
|
||||
version = "0.42.2"
|
||||
source = "registry+https://github.com/rust-lang/crates.io-index"
|
||||
checksum = "8de912b8b8feb55c064867cf047dda097f92d51efad5b491dfb98f6bbb70cb36"
|
||||
|
||||
[[package]]
|
||||
name = "windows_x86_64_gnullvm"
|
||||
version = "0.42.2"
|
||||
source = "registry+https://github.com/rust-lang/crates.io-index"
|
||||
checksum = "26d41b46a36d453748aedef1486d5c7a85db22e56aff34643984ea85514e94a3"
|
||||
|
||||
[[package]]
|
||||
name = "windows_x86_64_msvc"
|
||||
version = "0.42.2"
|
||||
source = "registry+https://github.com/rust-lang/crates.io-index"
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||||
checksum = "9aec5da331524158c6d1a4ac0ab1541149c0b9505fde06423b02f5ef0106b9f0"
|
||||
@ -1,9 +0,0 @@
|
||||
[workspace]
|
||||
|
||||
[package]
|
||||
name = "elevator"
|
||||
version = "0.1.0"
|
||||
edition = "2021"
|
||||
|
||||
[dependencies]
|
||||
tokio = { version = "1.26.0", features = ["full"] }
|
||||
@ -1,234 +0,0 @@
|
||||
//! The building simulates floors and elevators.
|
||||
|
||||
use tokio::sync::{broadcast, mpsc};
|
||||
use tokio::task;
|
||||
use tokio::time;
|
||||
|
||||
#[derive(Debug, Clone)]
|
||||
pub enum Direction {
|
||||
Up,
|
||||
Down,
|
||||
}
|
||||
|
||||
/// A passenger is a person with a destination floor in mind.
|
||||
#[derive(Debug)]
|
||||
struct Passenger {
|
||||
destination: FloorId,
|
||||
}
|
||||
|
||||
/// FloorId identifies a floor. These are zero-based integers.
|
||||
pub type FloorId = usize;
|
||||
|
||||
/// Floor represents the current status of a floor in the building.
|
||||
#[derive(Default, Debug)]
|
||||
struct Floor {
|
||||
passengers: Vec<Passenger>,
|
||||
}
|
||||
|
||||
/// ElevatorId identifies an elevator in the building. These are zero-based integers.
|
||||
pub type ElevatorId = usize;
|
||||
|
||||
/// Elevator represents the current status of an elevator in the building.
|
||||
#[derive(Default, Debug)]
|
||||
struct Elevator {
|
||||
/// Floor the elevator is currently on. In the simulation the elevator
|
||||
/// transports instantaneously from one floor to the next in a single
|
||||
/// simulation tick.
|
||||
position: FloorId,
|
||||
/// Destination floor for the elevator, if any. This can change at any time.
|
||||
destination: Option<FloorId>,
|
||||
/// Passengers currently on the elevator.
|
||||
passengers: Vec<Passenger>,
|
||||
/// True if the elevator is stopped with the doors open. The elevator
|
||||
/// will not move with the doors open, but they will close at the next
|
||||
/// tick of the simulation.
|
||||
doors_open: bool,
|
||||
}
|
||||
|
||||
/// A BuildingEvent is an event that occurs in the building.
|
||||
#[derive(Debug, Clone)]
|
||||
pub enum BuildingEvent {
|
||||
/// A passenger has pressed a floor button in the elevator.
|
||||
FloorButtonPressed(ElevatorId, FloorId),
|
||||
/// A passenger on the given floor has pressed the call button.
|
||||
CallButtonPressed(FloorId, Direction),
|
||||
/// The elevator has arrived at the given floor. If this is the
|
||||
/// elevator's destination, then it will stop open its doors.
|
||||
AtFloor(ElevatorId, FloorId),
|
||||
/// A passenger has been delivered to their desired floor.
|
||||
PassengerDelivered(FloorId),
|
||||
}
|
||||
|
||||
/// A BuildingCommand tells the building what to do.
|
||||
#[derive(Debug)]
|
||||
pub enum BuildingCommand {
|
||||
/// Set the elevator's destination. The elevator will close its doors
|
||||
/// if necessary and then begin moving toward this floor.
|
||||
GoToFloor(ElevatorId, FloorId),
|
||||
}
|
||||
|
||||
/// A DriverCommand is a message from the driver to change the state of
|
||||
/// the building.
|
||||
#[derive(Debug)]
|
||||
pub enum DriverCommand {
|
||||
/// A passenger has arrived and is waiting for an elevator. The passenger will automatically
|
||||
/// press the relevant call button, board the elevator when it arrives, press their floor
|
||||
/// button, and depart when the doors open on their destination floor.
|
||||
PassengerArrived { at: FloorId, destination: FloorId },
|
||||
|
||||
/// Halt all activity in the building and end the building task.
|
||||
Halt,
|
||||
}
|
||||
|
||||
/// Building manages the current status of the building.
|
||||
#[derive(Debug)]
|
||||
pub struct Building {
|
||||
floors: Vec<Floor>,
|
||||
elevators: Vec<Elevator>,
|
||||
}
|
||||
|
||||
impl Building {
|
||||
pub fn new(num_floors: usize, num_elevators: usize) -> Self {
|
||||
let mut floors = vec![];
|
||||
for _ in 0..num_floors {
|
||||
floors.push(Floor::default());
|
||||
}
|
||||
let mut elevators = vec![];
|
||||
for _ in 0..num_elevators {
|
||||
elevators.push(Elevator::default());
|
||||
}
|
||||
Self { floors, elevators }
|
||||
}
|
||||
|
||||
/// Start the building. The resulting channels are used to communicate
|
||||
/// with the building
|
||||
pub fn start(
|
||||
self,
|
||||
) -> (
|
||||
task::JoinHandle<()>,
|
||||
broadcast::Receiver<BuildingEvent>,
|
||||
mpsc::Sender<BuildingCommand>,
|
||||
mpsc::Sender<DriverCommand>,
|
||||
) {
|
||||
let (events_tx, events_rx) = broadcast::channel(10);
|
||||
let (building_cmd_tx, building_cmd_rx) = mpsc::channel(10);
|
||||
let (driver_cmd_tx, driver_cmd_rx) = mpsc::channel(10);
|
||||
let task = tokio::spawn(self.run(events_tx, building_cmd_rx, driver_cmd_rx));
|
||||
(task, events_rx, building_cmd_tx, driver_cmd_tx)
|
||||
}
|
||||
|
||||
async fn run(
|
||||
mut self,
|
||||
events_tx: broadcast::Sender<BuildingEvent>,
|
||||
mut building_cmd_rx: mpsc::Receiver<BuildingCommand>,
|
||||
mut driver_cmd_rx: mpsc::Receiver<DriverCommand>,
|
||||
) {
|
||||
let mut ticker = time::interval(time::Duration::from_millis(100));
|
||||
loop {
|
||||
tokio::select! {
|
||||
Some(BuildingCommand::GoToFloor(el, fl)) = building_cmd_rx.recv() => {
|
||||
self.elevators[el].destination = Some(fl);
|
||||
}
|
||||
Some(cmd) = driver_cmd_rx.recv() => {
|
||||
match cmd {
|
||||
DriverCommand::PassengerArrived{at, destination} => {
|
||||
self.new_passenger(&events_tx, at, destination).await;
|
||||
}
|
||||
DriverCommand::Halt => return,
|
||||
}
|
||||
}
|
||||
_ = ticker.tick() => self.move_elevators(&events_tx).await
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/// Move the elevators toward their destinations.
|
||||
async fn move_elevators(&mut self, events_tx: &broadcast::Sender<BuildingEvent>) {
|
||||
for el in 0..self.elevators.len() {
|
||||
let elevator = &mut self.elevators[el];
|
||||
|
||||
// If the elevator's doors are open, close them and wait for the next tick.
|
||||
if elevator.doors_open {
|
||||
elevator.doors_open = false;
|
||||
continue;
|
||||
}
|
||||
|
||||
// If the elevator has somewhere to go, move toward it.
|
||||
if let Some(dest) = elevator.destination {
|
||||
if dest > elevator.position {
|
||||
elevator.position += 1;
|
||||
}
|
||||
if dest < elevator.position {
|
||||
elevator.position -= 1;
|
||||
}
|
||||
events_tx
|
||||
.send(BuildingEvent::AtFloor(el, elevator.position))
|
||||
.unwrap();
|
||||
|
||||
// If the elevator has reached its destination, open
|
||||
// the doors and let passengers get on and off.
|
||||
if elevator.position == dest {
|
||||
elevator.destination = None;
|
||||
elevator.doors_open = true;
|
||||
self.exchange_passengers(&events_tx, el).await;
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/// Handle a new passenger arriving at the given floor.
|
||||
async fn new_passenger(
|
||||
&mut self,
|
||||
events_tx: &broadcast::Sender<BuildingEvent>,
|
||||
at: FloorId,
|
||||
destination: FloorId,
|
||||
) {
|
||||
println!("Passenger arrived at {} going to {}", at, destination);
|
||||
if at == destination {
|
||||
events_tx
|
||||
.send(BuildingEvent::PassengerDelivered(destination))
|
||||
.unwrap();
|
||||
return;
|
||||
}
|
||||
|
||||
self.floors[at].passengers.push(Passenger { destination });
|
||||
let dir = if at < destination {
|
||||
Direction::Up
|
||||
} else {
|
||||
Direction::Down
|
||||
};
|
||||
events_tx
|
||||
.send(BuildingEvent::CallButtonPressed(at, dir))
|
||||
.unwrap();
|
||||
}
|
||||
|
||||
/// The doors for the given elevator are open, so take on and discharge passengers.
|
||||
async fn exchange_passengers(
|
||||
&mut self,
|
||||
events_tx: &broadcast::Sender<BuildingEvent>,
|
||||
el: ElevatorId,
|
||||
) {
|
||||
let elevator = &mut self.elevators[el];
|
||||
let fl = elevator.position;
|
||||
|
||||
// Handle passengers leaving the elevator at their floor.
|
||||
let (this_floor, other_floors): (Vec<Passenger>, Vec<Passenger>) = elevator
|
||||
.passengers
|
||||
.drain(..)
|
||||
.partition(|px| px.destination == fl);
|
||||
for px in this_floor {
|
||||
events_tx
|
||||
.send(BuildingEvent::PassengerDelivered(px.destination))
|
||||
.unwrap();
|
||||
}
|
||||
elevator.passengers = other_floors;
|
||||
|
||||
// Handle passengers entering the elevator.
|
||||
for px in self.floors[fl].passengers.drain(..) {
|
||||
events_tx
|
||||
.send(BuildingEvent::FloorButtonPressed(el, px.destination))
|
||||
.unwrap();
|
||||
elevator.passengers.push(px);
|
||||
}
|
||||
}
|
||||
}
|
||||
@ -1,28 +0,0 @@
|
||||
//! The controller directs the elevators to operate so that passengers
|
||||
//! get to their destinations.
|
||||
|
||||
use crate::building::{BuildingCommand, BuildingEvent};
|
||||
use tokio::sync::{broadcast, mpsc};
|
||||
|
||||
pub async fn controller(
|
||||
mut events_rx: broadcast::Receiver<BuildingEvent>,
|
||||
building_cmd_tx: mpsc::Sender<BuildingCommand>,
|
||||
) {
|
||||
while let Ok(evt) = events_rx.recv().await {
|
||||
match evt {
|
||||
BuildingEvent::CallButtonPressed(at, _) => {
|
||||
building_cmd_tx
|
||||
.send(BuildingCommand::GoToFloor(0, at))
|
||||
.await
|
||||
.unwrap();
|
||||
}
|
||||
BuildingEvent::FloorButtonPressed(_, destination) => {
|
||||
building_cmd_tx
|
||||
.send(BuildingCommand::GoToFloor(0, destination))
|
||||
.await
|
||||
.unwrap();
|
||||
}
|
||||
_ => {}
|
||||
}
|
||||
}
|
||||
}
|
||||
@ -1,35 +0,0 @@
|
||||
//! The driver controls when and where passengers arrive.
|
||||
|
||||
use crate::building::{Building, BuildingEvent, DriverCommand};
|
||||
use tokio::sync::{broadcast, mpsc};
|
||||
|
||||
/// Create a new building to be driven by this driver.
|
||||
pub fn make_building() -> Building {
|
||||
Building::new(3, 1)
|
||||
}
|
||||
|
||||
/// Simulate people arriving at the ground floor and going to the first floor, one by one.
|
||||
pub async fn driver(
|
||||
mut events_rx: broadcast::Receiver<BuildingEvent>,
|
||||
driver_cmd_tx: mpsc::Sender<DriverCommand>,
|
||||
) {
|
||||
for _ in 0..3 {
|
||||
// A passenger has arrived..
|
||||
driver_cmd_tx
|
||||
.send(DriverCommand::PassengerArrived {
|
||||
at: 0,
|
||||
destination: 2,
|
||||
})
|
||||
.await
|
||||
.unwrap();
|
||||
|
||||
// Wait until they are delivered..
|
||||
while let Ok(evt) = events_rx.recv().await {
|
||||
if let BuildingEvent::PassengerDelivered(_) = evt {
|
||||
break;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
driver_cmd_tx.send(DriverCommand::Halt).await.unwrap();
|
||||
}
|
||||
@ -1,23 +0,0 @@
|
||||
use building::BuildingEvent;
|
||||
use tokio::sync::broadcast;
|
||||
|
||||
mod building;
|
||||
mod controller;
|
||||
mod driver;
|
||||
|
||||
#[tokio::main]
|
||||
async fn main() {
|
||||
let building = driver::make_building();
|
||||
let (building_task, events_rx, building_cmd_tx, driver_cmd_tx) = building.start();
|
||||
|
||||
tokio::spawn(print_events(events_rx.resubscribe()));
|
||||
tokio::spawn(driver::driver(events_rx.resubscribe(), driver_cmd_tx));
|
||||
tokio::spawn(controller::controller(events_rx, building_cmd_tx));
|
||||
building_task.await.unwrap();
|
||||
}
|
||||
|
||||
async fn print_events(mut events_rx: broadcast::Receiver<BuildingEvent>) {
|
||||
while let Ok(evt) = events_rx.recv().await {
|
||||
println!("BuildingEvent::{:?}", evt);
|
||||
}
|
||||
}
|
||||
@ -8,3 +8,19 @@
|
||||
{{#include dining-philosophers-async.rs}}
|
||||
```
|
||||
|
||||
## Broadcast Chat Application
|
||||
|
||||
([back to exercise](chat-app.md))
|
||||
|
||||
`src/bin/server.rs`:
|
||||
|
||||
```rust,compile_fail
|
||||
{{#include chat-async/src/bin/server.rs}}
|
||||
```
|
||||
|
||||
`src/bin/client.rs`:
|
||||
|
||||
```rust,compile_fail
|
||||
{{#include chat-async/src/bin/client.rs}}
|
||||
```
|
||||
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user