feat: add methods to get the current used parallelism (#24)

Author: dsherret

src/parallelism.rs

@@ -64,9 +64,25 @@ impl Parallelism {
   ///
   /// Note that increasing the parallelism beyond the max
   /// parallelism won't do anything.
-  pub fn set_parallelism(&self, parallelism: NonZeroUsize) {
+  pub fn set_max(&self, parallelism: NonZeroUsize) {
     self.sempahore.set_max(parallelism);
   }
+
+  #[deprecated = "use set_max instead"]
+  pub fn set_parallelism(&self, parallelism: NonZeroUsize) {
+    self.set_max(parallelism);
+  }
+
+  /// Current set parallelism.
+  pub fn current_max(&self) -> usize {
+    self.sempahore.current_max()
+  }
+
+  /// Current amount of active parallelism which may be greater
+  /// or less than the max parallelism.
+  pub fn current_used(&self) -> usize {
+    self.sempahore.current_used()
+  }
 }
 
 impl ParallelismProvider for Parallelism {

src/utils/semaphore.rs

@@ -42,6 +42,14 @@ impl Semaphore {
     }
   }
 
+  pub fn current_used(&self) -> usize {
+    self.permits.lock().used
+  }
+
+  pub fn current_max(&self) -> usize {
+    self.permits.lock().max
+  }
+
   pub fn set_max(&self, n: NonZeroUsize) {
     let mut permits = self.permits.lock();
     let is_greater = n.get() > permits.max;