[BlockLiteral] Add convenience method for simple scenarios to reduce boilerplate

src/ObjCRuntime/Blocks.cs

@@ -295,6 +295,43 @@ namespace ObjCRuntime {
 
 		[DllImport (Messaging.LIBOBJC_DYLIB)]
 		static extern IntPtr _Block_copy (ref BlockLiteral block);
+
+		delegate void dispatch_block_t (IntPtr block);
+		static dispatch_block_t static_dispatch_block_t = TrampolineDispatchBlock;
+
+		[MonoPInvokeCallback (typeof (dispatch_block_t))]
+		static unsafe void TrampolineDispatchBlock (IntPtr block)
+		{
+			var descriptor = (BlockLiteral *) block;
+			var del = (Action) (descriptor->Target);
+			if (del != null){
+			        del ();
+			}
+		}
+
+		//
+		// Simple method that we can use to wrap methods that need to call a block
+		//
+		// usage:
+		// void MyCallBack () {} 
+		// BlockLiteral.SimpleCall (MyCallBack, (x) => my_PINvokeThatTakesaBlock (x));
+		//  The above will call the unmanaged my_PINvokeThatTakesaBlock method with a block
+		// that when invoked will call MyCallback
+		//
+		internal unsafe static void SimpleCall  (Action callbackToInvoke, Action <IntPtr> pinvoke)
+		{
+			unsafe {
+			        BlockLiteral *block_ptr_handler;
+			        BlockLiteral block_handler;
+			        block_handler = new BlockLiteral ();
+			        block_ptr_handler = &block_handler;
+			        block_handler.SetupBlockUnsafe (static_dispatch_block_t, callbackToInvoke);
+
+				pinvoke ((IntPtr) block_ptr_handler);
+			        block_ptr_handler->CleanupBlock ();
+			}
+		}
+		
 #endif
 	}