pub-sub 2.0.0

// Copyright (c) 2016 creato
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#![warn(missing_docs)]

//! A basic publish/subscribe channel.
//!
//! # Usage
//!
//! Add to crate dependencies:
//!
//! ```toml
//! [dependencies]
//! pub-sub = "*"
//! ```
//! Import in crate root:
//!
//! ```
//! extern crate pub_sub;
//! ```
//!
//! # Example
//!
//! ```
//! extern crate pub_sub;
//! extern crate uuid;
//!
//! use std::thread;
//! use uuid::Uuid;
//!
//! fn main() {
//!    let channel = pub_sub::PubSub::new();
//!
//!    let mut handles = vec![];
//!
//!    for _ in 0..16 {
//!        let recv = channel.subscribe();
//!
//!         handles.push(thread::spawn(move || {
//!             for _ in 0..16 {
//!                 println!("recevied {}", recv.recv().unwrap());
//!             }
//!         }));
//!     }
//!
//!     for _ in 0..16 {
//!         let channel = channel.clone();
//!
//!         handles.push(thread::spawn(move || {
//!             let msg_id = Uuid::new_v4();
//!             println!("    sent {}", msg_id);
//!             channel.send(msg_id).unwrap();
//!         }));
//!     }
//!
//!     while let Some(handle) = handles.pop() {
//!         handle.join().unwrap();
//!     }
//! }
//! ```


extern crate uuid;

use std::sync::{mpsc, Arc, Mutex};
use std::collections::HashMap;


/// Pub/sub channel.
#[derive(Clone)]
pub struct PubSub<T: Clone> {
    senders: Arc<Mutex<HashMap<uuid::Uuid, mpsc::Sender<T>>>>,
}

/// Subscription to a pub/sub channel
pub struct Subscription<T: Clone> {
    receiver: mpsc::Receiver<T>,
    senders: Arc<Mutex<HashMap<uuid::Uuid, mpsc::Sender<T>>>>,
    id: uuid::Uuid,
}

impl<T: Clone> PubSub<T> {
    /// Create a pub/sub channel
    pub fn new() -> PubSub<T> {
        PubSub { senders: Arc::new(Mutex::new(HashMap::new())) }
    }

    /// Attempts to broadcast
    pub fn send(&self, it: T) -> Result<(), mpsc::SendError<T>> {
        let senders = self.senders.lock().unwrap();

        for (_, sender) in senders.iter() {
            match sender.send(it.clone()) {
                Ok(_) => {}
                Err(err) => return Err(err),
            }
        }

        Ok(())
    }

    /// Create a new subscription to the channel.
    pub fn subscribe(&self) -> Subscription<T> {
        let id = uuid::Uuid::new_v4();
        let (send, recv) = mpsc::channel();

        {
            let mut senders = self.senders.lock().unwrap();
            senders.insert(id, send);
        }

        Subscription {
            receiver: recv,
            senders: self.senders.clone(),
            id: id,
        }
    }
}

impl<T: Clone> Subscription<T> {
    /// Receives a single message. Blocks until a message is available.
    pub fn recv(&self) -> Result<T, mpsc::RecvError> {
        self.receiver.recv()
    }

    /// Tries to receive a single message, not blocking if one is not available.
    pub fn try_recv(&self) -> Result<T, mpsc::TryRecvError> {
        self.receiver.try_recv()
    }

    /// Creates an iterator that will block waiting for messages.
    pub fn iter(&self) -> mpsc::Iter<T> {
        self.receiver.iter()
    }
}

impl<T: Clone> Drop for Subscription<T> {
    /// Remove our sender ID from the sender list.
    fn drop(&mut self) {
        let mut senders = self.senders.lock().unwrap();
        senders.remove(&self.id);
    }
}

impl<T: Clone> Clone for Subscription<T> {
    fn clone(&self) -> Self {
        PubSub { senders: self.senders.clone() }.subscribe()
    }
}


#[cfg(test)]
mod tests {
    use std;

    use super::*;

    #[test]
    fn many_senders() {
        use std::sync::atomic::{AtomicUsize, Ordering};

        let send = PubSub::new();
        let recv = send.subscribe();

        let threads = 5;
        let pulses = 50;

        let received = std::sync::Arc::new(AtomicUsize::new(0));

        for _ in 0..threads {
            let recv = recv.clone();
            let received = received.clone();
            std::thread::spawn(move || {
                while let Ok(_) = recv.recv() {
                    received.fetch_add(1, Ordering::AcqRel);
                }
            });
        }

        let mut accum = 0;

        for _ in 0..pulses {
            accum += 1;
            send.send(accum).unwrap();
        }

        std::thread::sleep(std::time::Duration::from_millis(75));
        assert_eq!(received.load(Ordering::Acquire), threads * pulses);
    }
}