Common: Add a Semaphore wrapper class

Source/Core/Common/Common.vcxproj

@@ -125,6 +125,7 @@
     <ClInclude Include="Profiler.h" />
     <ClInclude Include="ScopeGuard.h" />
     <ClInclude Include="SDCardUtil.h" />
+    <ClInclude Include="Semaphore.h" />
     <ClInclude Include="SettingsHandler.h" />
     <ClInclude Include="StringUtil.h" />
     <ClInclude Include="SymbolDB.h" />

Source/Core/Common/Common.vcxproj.filters

@@ -225,6 +225,7 @@
     <ClInclude Include="Assert.h" />
     <ClInclude Include="NonCopyable.h" />
     <ClInclude Include="Analytics.h" />
+    <ClInclude Include="Semaphore.h" />
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="BreakPoints.cpp" />

Source/Core/Common/Semaphore.h

@@ -0,0 +1,50 @@
+// Copyright 2016 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#ifdef _WIN32
+
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+#include <Windows.h>
+
+namespace Common
+{
+class Semaphore
+{
+public:
+  Semaphore(int initial_count, int maximum_count)
+  {
+    m_handle = CreateSemaphoreA(nullptr, initial_count, maximum_count, nullptr);
+  }
+
+  ~Semaphore() { CloseHandle(m_handle); }
+  void Wait() { WaitForSingleObject(m_handle, INFINITE); }
+  void Post() { ReleaseSemaphore(m_handle, 1, nullptr); }
+private:
+  HANDLE m_handle;
+};
+}  // namespace Common
+
+#else  // _WIN32
+
+#include <semaphore.h>
+
+namespace Common
+{
+class Semaphore
+{
+public:
+  Semaphore(int initial_count, int maximum_count) { sem_init(&m_handle, 0, initial_count); }
+  ~Semaphore() { sem_destroy(&m_handle); }
+  void Wait() { sem_wait(&m_handle); }
+  void Post() { sem_post(&m_handle); }
+private:
+  sem_t m_handle;
+};
+}  // namespace Common
+
+#endif  // _WIN32