Implement sync module

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "rpools"
-version = "0.2.4"
+version = "0.3.0"
 authors = ["jcbritobr <jcbritobr@gmail.com>"]
 edition = "2018"
 repository = "https://github.com/jgardona/rpools"

README.md

@@ -19,8 +19,15 @@
 
 A minimalist rust workerpool implementation that uses channels to synchronize the jobs. It can spawn a fixed number of worker threads, that waits for a job queue.
 
+## Install
 
-* Use
+```
+$ cargo add rpools
+``` 
+
+## Usage
+
+* **A simple workerpool**
 ```rust
  use rpools::pool::WorkerPool;
  use std::sync::mpsc::channel;
@@ -47,8 +54,26 @@ A minimalist rust workerpool implementation that uses channels to synchronize th
  assert_eq!(rx.iter().take(n_jobs).fold(0, |a, b| a + b), 8);
 ```
 
-* Test
+* **Use sync module to synchronize your pool**
+
+```rust
+let njobs = 20;
+let nworkers = 3;
+let pool = pool::WorkerPool::new(nworkers);
+let atomic = Arc::new(AtomicUsize::new(0));
+let wg = WaitGroup::default();
+
+// send the jobs to the pool
+for _ in 0..njobs {
+    let wg = wg.clone();
+    let atomic = atomic.clone();
+    pool.execute(move || {
+        atomic.fetch_add(1, Ordering::Relaxed);
+        drop(wg);
+    });
+}
 
-```shell
-$ cargo test
+// wait for the pool finnishes
+wg.wait();
+assert_eq!(njobs, atomic.load(Ordering::Relaxed));
 ```

src/lib.rs

@@ -31,3 +31,4 @@
 
 // Imports and makes pool public.
 pub mod pool;
+pub mod sync;

src/pool.rs

@@ -18,6 +18,27 @@ type Handle = thread::JoinHandle<()>;
 /// Implements a continuous pool of rust threads thats doesn't stops
 /// unless it gets out of scope.
 ///
+/// ### Examples
+/// 
+/// let njobs = 20;
+/// let nworkers = 3;
+/// let pool = pool::WorkerPool::new(nworkers);
+/// let atomic = Arc::new(AtomicUsize::new(0));
+/// let wg = WaitGroup::default();
+/// 
+/// // send the jobs to the pool
+/// for _ in 0..njobs {
+///     let wg = wg.clone();
+///     let atomic = atomic.clone();
+///     pool.execute(move || {
+///         atomic.fetch_add(1, Ordering::Relaxed);
+///         drop(wg);
+///     });
+/// }
+/// 
+/// // wait for the pool finnishes
+/// wg.wait();
+/// assert_eq!(njobs, atomic.load(Ordering::Relaxed));
 pub struct WorkerPool {
     workers: Vec<Worker>,
     sender: mpsc::Sender<Job>,

src/sync.rs

@@ -0,0 +1,91 @@
+//! ## Sync
+//! 
+//! This module has data structures used to synchronize
+//! threads. WaitGroup is used to make a thread to wait
+//! others.
+//! 
+//! ### Examples
+//! ```
+//! use rpools::pool::WorkerPool;
+//! use std::sync::{atomic::AtomicUsize, atomic::Ordering, Arc, Mutex};
+//! use rpools::sync::WaitGroup;
+//! 
+//! let njobs = 20;
+//! let nworkers = 3;
+//! let pool = WorkerPool::new(nworkers);
+//! let atomic = Arc::new(AtomicUsize::new(0));
+//! let wg = WaitGroup::default();
+//! 
+//! // send the jobs to the pool
+//! for _ in 0..njobs {
+//!     let wg = wg.clone();
+//!     let atomic = atomic.clone();
+//!     pool.execute(move || {
+//!         atomic.fetch_add(1, Ordering::Relaxed);
+//!         drop(wg);
+//!     });
+//! }
+//! 
+//! // wait for the pool finnishes
+//! wg.wait();
+//! assert_eq!(njobs, atomic.load(Ordering::Relaxed));
+//! ```
+
+use std::sync::{
+    atomic::{AtomicUsize, Ordering},
+    Arc, Condvar, Mutex,
+};
+
+
+/// A data struct to store a counter, a mutex and a condvar.
+/// It is responsible and serves as semaphore to synchronize threads.
+#[derive(Default)]
+struct Wg {
+    counter: AtomicUsize,
+    mu: Mutex<bool>,
+    condvar: Condvar,
+}
+
+/// A public wrapper above Wg. This data structure is responsible
+/// to do the logics of the semaphore, block the target thread and
+/// wait for signals to continue processing.
+#[derive(Default)]
+pub struct WaitGroup(Arc<Wg>);
+
+impl WaitGroup {
+    /// Blocks the current thread and waits until counter becomes 0. If
+    /// counter is 0, start processing again.
+    pub fn wait(&self) {
+        let mut started = self.0.mu.lock().expect("Cant get the lock");
+        while !*started {
+            started = self
+                .0
+                .condvar
+                .wait(started)
+                .expect("Cant block the current thread");
+            if self.0.counter.load(Ordering::Relaxed) == 0 {
+                *started = true;
+            }
+        }
+    }
+}
+
+/// Implements Clone for WaitGroup
+impl Clone for WaitGroup {
+    /// For each clone of this struct, increments the
+    /// counter in one.
+    fn clone(&self) -> Self {
+        self.0.counter.fetch_add(1, Ordering::Relaxed);
+        Self(self.0.clone())
+    }
+}
+
+/// Implements Drop for WaitGroup
+impl Drop for WaitGroup {
+    /// When a shared reference goes out of scope,
+    /// decrement the counter in one.
+    fn drop(&mut self) {
+        self.0.counter.fetch_sub(1, Ordering::Relaxed);
+        self.0.condvar.notify_one();
+    }
+}

tests/integration.rs

@@ -1,6 +1,33 @@
-use std::{sync::mpsc, sync::Arc, sync::Mutex};
+use std::{
+    sync::mpsc,
+    sync::{atomic::AtomicUsize, Mutex},
+    sync::{atomic::Ordering, Arc},
+};
 
-use rpools::pool;
+use rpools::{pool, sync::WaitGroup};
+
+#[test]
+fn test_waitgroup() {
+    let njobs = 20;
+    let nworkers = 3;
+    let pool = pool::WorkerPool::new(nworkers);
+    let atomic = Arc::new(AtomicUsize::new(0));
+    let wg = WaitGroup::default();
+
+    // send the jobs to the pool
+    for _ in 0..njobs {
+        let wg = wg.clone();
+        let atomic = atomic.clone();
+        pool.execute(move || {
+            atomic.fetch_add(1, Ordering::Relaxed);
+            drop(wg);
+        });
+    }
+
+    // wait for the pool finnishes
+    wg.wait();
+    assert_eq!(njobs, atomic.load(Ordering::Relaxed));
+}
 
 #[test]
 fn pool_should_synchronize_sender_and_receiver_and_fold_results() {