async1: Read input from files

Author: senekor

dev/Cargo.toml

@@ -199,7 +199,7 @@ edition = "2024"
 publish = false
 
 [dependencies]
-tokio = { version = "1", features = ["rt"] }
+tokio = { version = "1", features = ["fs", "macros", "rt", "rt-multi-thread"] }
 
 [profile.release]
 panic = "abort"

exercises/24_async/async1.rs

@@ -4,39 +4,38 @@
 // together, they can finish the job much faster.
 //
 // Let's simulate this using asynchronous programming. Each person is
-// represented as an asynchronous task, which can be executed concurrently (i.e.
-// they can be doing the calculations at the same time).
-
-fn main() {
-    // Async tasks need to be executed by a "runtime", which is not provided by
-    // Rust's standard library. Here, we use the mainstream runtime `tokio`.
-    let rt = tokio::runtime::Builder::new_current_thread()
-        .build()
-        .unwrap();
-
-    let scores_class_a = &[83, 77, 92];
-    let scores_class_b = &[84, 88, 96];
-    let scores_class_c = &[71, 83, 76];
+// represented as an asynchronous task, which can be executed concurrently.
 
+// Async tasks need to be executed by a "runtime", which is not provided by
+// Rust's standard library. Here, we use the mainstream runtime `tokio`.
+// The macro `tokio::main` wraps the entire main function in a runtime.
+#[tokio::main]
+async fn main() {
     // TODO: Fix the compiler errors by making the spawned function async.
-    let alice = rt.spawn(calculate_mean_score(scores_class_a));
-    let bob = rt.spawn(calculate_mean_score(scores_class_b));
-    let catherine = rt.spawn(calculate_mean_score(scores_class_c));
-
-    // Block the runtime on a task that awaits all three calculations.
-    let [mean_score_a, mean_score_b, mean_score_c]: [usize; _] = rt.block_on(async {
-        [
-            // TODO: "await" all three tasks to fix the compiler error.
-            alice, bob, catherine,
-        ]
-    });
+    let mean_score_a = tokio::spawn(calculate_mean_score("input_files/scores_class_a.txt"));
+    let mean_score_b = tokio::spawn(calculate_mean_score("input_files/scores_class_b.txt"));
+    let mean_score_c = tokio::spawn(calculate_mean_score("input_files/scores_class_c.txt"));
 
-    assert_eq!(mean_score_a, 84);
-    assert_eq!(mean_score_b, 89);
-    assert_eq!(mean_score_c, 76);
+    // TODO: Await the spawned tasks to check their results.
+    assert_eq!(mean_score_a, 84); // alice
+    assert_eq!(mean_score_b, 89); // bob
+    assert_eq!(mean_score_c, 76); // catherine
 }
 
-fn calculate_mean_score(score_list: &[usize]) -> usize {
-    let score_sum: usize = score_list.iter().sum();
-    score_sum / score_list.len()
+// TODO: Fix the compiler errors by making the spawned function async.
+fn calculate_mean_score(scores_file: &str) -> usize {
+    // Read the file asynchronously
+    let file = tokio::fs::read_to_string(scores_file).await.unwrap();
+
+    // Initialize the sum and the number of scores
+    let mut sum = 0;
+    let mut n = 0;
+    for line in file.lines() {
+        // Parse every line as a score
+        let score = line.parse::<usize>().unwrap();
+        sum += score;
+        n += 1;
+    }
+
+    sum / n
 }

input_files/scores_class_a.txt

@@ -0,0 +1,3 @@
+83
+77
+92

input_files/scores_class_b.txt

@@ -0,0 +1,3 @@
+84
+88
+96

input_files/scores_class_c.txt

@@ -0,0 +1,3 @@
+71
+83
+76

rustlings-macros/info.toml

@@ -1225,3 +1225,12 @@ the functions "tim", "carl" and "nick".
 
 An async task can wait for another one to complete by "awaiting" it. Add
 ".await" after the three "task_name" variables in the "block_on" call."""
+
+[[input_files]]
+name = "scores_class_a.txt"
+
+[[input_files]]
+name = "scores_class_b.txt"
+
+[[input_files]]
+name = "scores_class_c.txt"

rustlings-macros/src/lib.rs

@@ -8,10 +8,16 @@ struct ExerciseInfo<'a> {
     dir: &'a str,
 }
 
+#[derive(Deserialize)]
+struct InputFileInfo<'a> {
+    name: &'a str,
+}
+
 #[derive(Deserialize)]
 struct InfoFile<'a> {
     #[serde(borrow)]
     exercises: Vec<ExerciseInfo<'a>>,
+    input_files: Vec<InputFileInfo<'a>>,
 }
 
 #[proc_macro]
@@ -25,9 +31,8 @@ pub fn include_files(_: TokenStream) -> TokenStream {
             .collect(),
     )
     .expect("Failed to parse `info.toml` as UTF8");
-    let exercises = toml::de::from_str::<InfoFile>(&info_file)
-        .expect("Failed to parse `info.toml`")
-        .exercises;
+    let info = toml::de::from_str::<InfoFile>(&info_file).expect("Failed to parse `info.toml`");
+    let exercises = &info.exercises;
 
     let exercise_files = exercises
         .iter()
@@ -54,11 +59,18 @@ pub fn include_files(_: TokenStream) -> TokenStream {
         .iter()
         .map(|dir| format!("../exercises/{dir}/README.md"));
 
+    let input_file_names = info.input_files.iter().map(|f| f.name);
+    let input_file_paths = info
+        .input_files
+        .iter()
+        .map(|f| format!("../input_files/{}", f.name));
+
     quote! {
         EmbeddedFiles {
             info_file: #info_file,
             exercise_files: &[#(ExerciseFiles { exercise: include_bytes!(#exercise_files), solution: include_bytes!(#solution_files), dir_ind: #dir_inds }),*],
-            exercise_dirs: &[#(ExerciseDir { name: #dirs, readme: include_bytes!(#readmes) }),*]
+            exercise_dirs: &[#(ExerciseDir { name: #dirs, readme: include_bytes!(#readmes) }),*],
+            input_files: &[#(InputFile { name: #input_file_names, content: include_str!(#input_file_paths) }),*],
         }
     }
     .into()

solutions/24_async/async1.rs

@@ -4,39 +4,35 @@
 // together, they can finish the job much faster.
 //
 // Let's simulate this using asynchronous programming. Each person is
-// represented as an asynchronous task, which can be executed concurrently (i.e.
-// they can be doing the calculations at the same time).
+// represented as an asynchronous task, which can be executed concurrently.
 
-fn main() {
-    // Async tasks need to be executed by a "runtime", which is not provided by
-    // Rust's standard library. Here, we use the mainstream runtime `tokio`.
-    let rt = tokio::runtime::Builder::new_current_thread()
-        .build()
-        .unwrap();
+// Async tasks need to be executed by a "runtime", which is not provided by
+// Rust's standard library. Here, we use the mainstream runtime `tokio`.
+// The macro `tokio::main` wraps the entire main function in a runtime.
+#[tokio::main]
+async fn main() {
+    let mean_score_a = tokio::spawn(calculate_mean_score("input_files/scores_class_a.txt"));
+    let mean_score_b = tokio::spawn(calculate_mean_score("input_files/scores_class_b.txt"));
+    let mean_score_c = tokio::spawn(calculate_mean_score("input_files/scores_class_c.txt"));
 
-    let scores_class_a = &[83, 77, 92];
-    let scores_class_b = &[84, 88, 96];
-    let scores_class_c = &[71, 83, 76];
-
-    let alice = rt.spawn(calculate_mean_score(scores_class_a));
-    let bob = rt.spawn(calculate_mean_score(scores_class_b));
-    let catherine = rt.spawn(calculate_mean_score(scores_class_c));
+    assert_eq!(mean_score_a.await.unwrap(), 84); // alice
+    assert_eq!(mean_score_b.await.unwrap(), 89); // bob
+    assert_eq!(mean_score_c.await.unwrap(), 76); // catherine
+}
 
-    // Block the runtime on a task that awaits all three calculations.
-    let [mean_score_a, mean_score_b, mean_score_c]: [usize; _] = rt.block_on(async {
-        [
-            alice.await.unwrap(),
-            bob.await.unwrap(),
-            catherine.await.unwrap(),
-        ]
-    });
+async fn calculate_mean_score(scores_file: &str) -> usize {
+    // Read the file asynchronously
+    let file = tokio::fs::read_to_string(scores_file).await.unwrap();
 
-    assert_eq!(mean_score_a, 84);
-    assert_eq!(mean_score_b, 89);
-    assert_eq!(mean_score_c, 76);
-}
+    // Initialize the sum and the number of scores
+    let mut sum = 0;
+    let mut n = 0;
+    for line in file.lines() {
+        // Parse every line as a score
+        let score = line.parse::<usize>().unwrap();
+        sum += score;
+        n += 1;
+    }
 
-async fn calculate_mean_score(score_list: &[usize]) -> usize {
-    let score_sum: usize = score_list.iter().sum();
-    score_sum / score_list.len()
+    sum / n
 }

src/embedded.rs

@@ -19,6 +19,12 @@ struct ExerciseFiles {
     dir_ind: usize,
 }
 
+// Input files that may be read by exercises.
+pub struct InputFile {
+    pub name: &'static str,
+    pub content: &'static str,
+}
+
 fn create_dir_if_not_exists(path: &str) -> Result<()> {
     if let Err(e) = create_dir(path)
         && e.kind() != io::ErrorKind::AlreadyExists
@@ -58,6 +64,7 @@ pub struct EmbeddedFiles {
     pub info_file: &'static str,
     exercise_files: &'static [ExerciseFiles],
     pub exercise_dirs: &'static [ExerciseDir],
+    pub input_files: &'static [InputFile],
 }
 
 impl EmbeddedFiles {

src/init.rs

@@ -144,6 +144,15 @@ pub fn init() -> Result<()> {
             .with_context(|| format!("Failed to create the file {solution_path}"))?;
     }
 
+    // init input files
+    create_dir("input_files").context("Failed to create the directory `input_files`")?;
+    for input_file in EMBEDDED_FILES.input_files {
+        fs::write(
+            format!("input_files/{}", input_file.name),
+            input_file.content,
+        )?;
+    }
+
     let current_cargo_toml = include_str!("../dev-Cargo.toml");
     // Skip the first line (comment).
     let newline_ind = current_cargo_toml