Add as_raw() methods for queues, groups and semaphores.

src/group.rs

@@ -10,6 +10,7 @@ use crate::queue::Queue;
 /// allows for aggregate synchronization, so you can track when all the
 /// closures complete, even if they are running on different queues.
 #[derive(Debug)]
+#[repr(transparent)]
 pub struct Group {
     ptr: dispatch_group_t,
 }
@@ -80,6 +81,11 @@ impl Group {
         };
         result == 0
     }
+
+    /// Returns the raw underlying `dispatch_group_t` value.
+    pub fn as_raw(&self) -> dispatch_group_t {
+        self.ptr
+    }
 }
 
 unsafe impl Sync for Group { }

src/queue.rs

@@ -72,6 +72,7 @@ impl QueuePriority {
 /// For more information, see Apple's [Grand Central Dispatch reference](
 /// https://developer.apple.com/library/mac/documentation/Performance/Reference/GCD_libdispatch_Ref/index.html).
 #[derive(Debug)]
+#[repr(transparent)]
 pub struct Queue {
     pub(crate) ptr: dispatch_queue_t,
 }
@@ -281,6 +282,11 @@ impl Queue {
     pub fn suspend(&self) -> SuspendGuard {
         SuspendGuard::new(self)
     }
+
+    /// Returns the raw underlying `dispatch_queue_t` value.
+    pub fn as_raw(&self) -> dispatch_queue_t {
+        self.ptr
+    }
 }
 
 unsafe impl Sync for Queue { }

src/sem.rs

@@ -6,6 +6,7 @@ use crate::{time_after_delay, WaitTimeout};
 
 /// A counting semaphore.
 #[derive(Debug)]
+#[repr(transparent)]
 pub struct Semaphore {
     ptr: dispatch_semaphore_t,
 }
@@ -69,6 +70,11 @@ impl Semaphore {
         self.wait_timeout(timeout)?;
         Ok(SemaphoreGuard::new(self.clone()))
     }
+
+    /// Returns the raw underlying `dispatch_semaphore_t` value.
+    pub fn as_raw(&self) -> dispatch_semaphore_t {
+        self.ptr
+    }
 }
 
 unsafe impl Sync for Semaphore {}