diff --git a/CMakeLists.txt b/CMakeLists.txt
index 65050f8..e4a3585 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -102,6 +102,7 @@ set(BUILDAT_CORE_SRCS
 	src/impl/noise.cpp
 	src/impl/voxel_volume.cpp
 	src/impl/compress.cpp
+	src/impl/worker_thread.cpp
 )
 if(WIN32)
 	set(BUILDAT_CORE_SRCS ${BUILDAT_CORE_SRCS} src/impl/windows/file_watch.cpp)
diff --git a/src/interface/semaphore.h b/src/interface/semaphore.h
new file mode 100644
index 0000000..8a6df54
--- /dev/null
+++ b/src/interface/semaphore.h
@@ -0,0 +1,32 @@
+// http://www.apache.org/licenses/LICENSE-2.0
+// Copyright 2014 Perttu Ahola <celeron55@gmail.com>
+#pragma once
+#include "core/types.h"
+#ifdef _WIN32
+	#include "ports/windows_compat.h"
+#else
+	#include <semaphore.h>
+#endif
+
+namespace interface
+{
+	struct Semaphore
+	{
+		sem_t sem;
+
+		Semaphore(unsigned int value = 0){
+			sem_init(&sem, 0, value);
+		}
+		~Semaphore(){
+			sem_destroy(&sem);
+		}
+		void wait(){
+			sem_wait(&sem);
+		}
+		void post(){
+			sem_post(&sem);
+		}
+	};
+}
+
+// vim: set noet ts=4 sw=4: