shared/src/shared.rs

use std::sync::Arc;
use tokio::sync::{Mutex, MutexGuard};
use tokio::time::{timeout, Duration};

// #[derive(Clone)] See issue #2
pub struct Shared<T> {
    pub data: Arc<Mutex<T>>,
    /// Number of seconds to consider a dead lock
    pub lock_timeout: u64,
}

impl<T> Clone for Shared<T> {
    fn clone(&self) -> Self {
        Self {
            data: self.data.clone(),
            lock_timeout: self.lock_timeout,
        }
    }
}

impl<T> Shared<T> {
    /// Creates a new Shared of data T
    ///
    /// A lock timeout of 30 seconds is assigned by default (Use Shared::with_timeout to set the timeout yourself, or just edit the field as it is public)
    ///
    /// > Want to see a complete example, look at doc_example in the examples directory
    ///
    /// Example:
    /// ```
    /// use shared::Shared;
    ///
    /// // #[derive(Clone)]
    /// // Clone is no longer needed as of v0.2.0
    /// #[derive(Debug)]
    /// struct Person {
    ///     pub name: String,
    ///     pub age: u16
    /// }
    ///
    /// #[tokio::main]
    /// async fn main() {
    ///     let shared_data = Shared::new(Person{
    ///         name: "Test Dummy".to_string(),
    ///         age: 30
    ///     });
    /// }
    /// ```
    pub fn new(data: T) -> Self {
        Shared {
            data: Arc::new(Mutex::new(data)),
            lock_timeout: 30_u64,
        }
    }

    /// Creates a new Shared of data T with a given timeout in seconds
    pub fn with_timeout(data: T, timeout: u64) -> Self {
        Shared { data: Arc::new(Mutex::new(data)), lock_timeout: timeout }
    }

    /// Acquire lock
    ///
    /// Will wait so many seconds as defined by lock_timeout (This will panic once the timeout is reached)
    ///
    /// > Want to see a complete example, look at doc_example in the examples directory
    ///
    /// Using:
    /// ```
    /// // See Shared::new for creating a Shared<Person>
    ///
    /// { // Direct access
    ///     let person = shared_data.lock().await;
    ///     println!("{:?}", person);
    /// }
    ///
    /// // Using it as a parameter
    /// async fn get_older(shared: Shared<Person>) {
    ///     let mut person = shared.lock().await;
    ///     person.age += 1;
    /// }
    ///
    /// // Calling
    /// get_older(shared_data.clone()).await;
    /// ```
    pub async fn lock(&self) -> MutexGuard<'_, T> {
        let result = timeout(Duration::from_secs(self.lock_timeout), self.data.lock()).await;
        if let Ok(guard) = result {
            return guard;
        }
        panic!(
            "Failed to acquire lock in {} seconds.  Deadlock?",
            self.lock_timeout
        );
        // self.data.lock().await
    }
}