From 3980638612f0ae781b890bc4614e65c3660c34f2 Mon Sep 17 00:00:00 2001
From: PoroCYon <porocyon@titandemo.org>
Date: Wed, 9 Sep 2020 17:01:42 +0200
Subject: [PATCH] Use std::atomic instead of the windows-only primitives for
 atomic operations in the song renderer

---
 WaveSabreCore/CMakeLists.txt                  | 12 +++++-
 WaveSabrePlayerLib/CMakeLists.txt             |  4 ++
 .../WaveSabrePlayerLib/AtomicHelpers.h        | 40 +++++++++++++++++++
 WaveSabrePlayerLib/src/SongRenderer.cpp       |  5 ++-
 4 files changed, 58 insertions(+), 3 deletions(-)
 create mode 100644 WaveSabrePlayerLib/include/WaveSabrePlayerLib/AtomicHelpers.h

diff --git a/WaveSabreCore/CMakeLists.txt b/WaveSabreCore/CMakeLists.txt
index 31ca1e2e..d5b12291 100644
--- a/WaveSabreCore/CMakeLists.txt
+++ b/WaveSabreCore/CMakeLists.txt
@@ -54,7 +54,8 @@ add_library(WaveSabreCore
 	src/Thunder.cpp
 	src/Twister.cpp)
 
-target_link_libraries(WaveSabreCore Msacm32.lib)
+target_link_libraries(WaveSabreCore PUBLIC Msacm32.lib)
+
 target_include_directories(WaveSabreCore PUBLIC include)
 
 if(MSVC)
@@ -69,4 +70,13 @@ if(MSVC)
 		target_compile_options(WaveSabreCore PUBLIC
 			$<$<CONFIG:MinSizeRel>:/Zc:sizedDealloc->)
 	endif()
+else()
+	# assuming GCC or clang for now
+
+	if(CMAKE_BUILD_TYPE NOTEQUAL Debug)
+		set_property(TARGET WaveSabreCore PROPERTY INTERPROCEDURAL_OPTIMIZATION ON)
+		target_compile_options(WaveSabreCore
+			PUBLIC $<$<CONFIG:MinSizeRel>:-Os -fno-exceptions -fno-rtti -fno-stack-protector -fno-stack-check -fno-unwind-tables -fno-asynchronous-unwind-tables -fomit-frame-pointer -fno-threadsafe-statics>
+			PRIVATE $<$<CONFIG:MinSizeRel>:-fno-math-errno -march=nocona -ffunction-sections -fdata-sections -Wl,--gc-sections)
+	endif()
 endif()
diff --git a/WaveSabrePlayerLib/CMakeLists.txt b/WaveSabrePlayerLib/CMakeLists.txt
index 6a0149d4..75a5b2fe 100644
--- a/WaveSabrePlayerLib/CMakeLists.txt
+++ b/WaveSabrePlayerLib/CMakeLists.txt
@@ -1,4 +1,5 @@
 add_library(WaveSabrePlayerLib
+	include/WaveSabrePlayerLib/AtomicHelpers.h
 	include/WaveSabrePlayerLib/CriticalSection.h
 	include/WaveSabrePlayerLib/PreRenderPlayer.h
 	include/WaveSabrePlayerLib/WavWriter.h
@@ -28,4 +29,7 @@ if(MSVC)
 		$<$<CONFIG:MinSizeRel>:/EHs-c->)
 	set_property(TARGET WaveSabrePlayerLib APPEND_STRING PROPERTY STATIC_LIBRARY_FLAGS_MINSIZEREL
 		" /LTCG")
+else()
+	# we need C++11 for std::atomic
+	set_property(TARGET WaveSabrePlayerLib PROPERTY CXX_STANDARD 11)
 endif()
diff --git a/WaveSabrePlayerLib/include/WaveSabrePlayerLib/AtomicHelpers.h b/WaveSabrePlayerLib/include/WaveSabrePlayerLib/AtomicHelpers.h
new file mode 100644
index 00000000..f3d20ab0
--- /dev/null
+++ b/WaveSabrePlayerLib/include/WaveSabrePlayerLib/AtomicHelpers.h
@@ -0,0 +1,40 @@
+#ifndef __WAVESABREPLAYERLIB_ATOMIC_HELPERS_H__
+#define __WAVESABREPLAYERLIB_ATOMIC_HELPERS_H__
+
+#ifdef _WIN32
+#include <Windows.h>
+#else
+#include <atomic>
+#endif
+
+namespace WaveSabreCore
+{
+	namespace AtomicHelpers
+	{
+		template<typename T>
+		inline bool CmpXchg(T* value, T newval, T expect)
+		{
+#ifdef _WIN32
+			return InterlockedCompareExchange((unsigned int*)value,
+					(unsigned int)newval, (unsigned int)expect)
+				== (unsigned int)expect;
+#else
+			return std::atomic_compare_exchange_strong((std::atomic_int*)value,
+					(int*)&expect, newval);
+#endif
+		}
+
+		template<typename T>
+		inline T XDec(T* value)
+		{
+#ifdef _WIN32
+			return (T)InterlockedDecrement((unsigned int*)value);
+#else
+			// returns the value *before* the call
+			return (T)(std::atomic_fetch_sub((std::atomic_int*)value, 1) - 1);
+#endif
+		}
+	}
+}
+
+#endif
diff --git a/WaveSabrePlayerLib/src/SongRenderer.cpp b/WaveSabrePlayerLib/src/SongRenderer.cpp
index 4923ac72..4c50f4ba 100644
--- a/WaveSabrePlayerLib/src/SongRenderer.cpp
+++ b/WaveSabrePlayerLib/src/SongRenderer.cpp
@@ -1,3 +1,4 @@
+#include <WaveSabrePlayerLib/AtomicHelpers.h>
 #include <WaveSabrePlayerLib/SongRenderer.h>
 
 using namespace WaveSabreCore;
@@ -195,7 +196,7 @@ namespace WaveSabrePlayerLib
 
 				// We have a free track that we can work on, yay!
 				//  Let's try to mark it so that no other thread takes it
-				if ((TrackRenderState)InterlockedCompareExchange((unsigned int *)&trackRenderStates[i], (unsigned int)TrackRenderState::Rendering, (unsigned int)TrackRenderState::Idle) == TrackRenderState::Idle)
+				if (AtomicHelpers::CmpXchg(&trackRenderStates[i], TrackRenderState::Rendering, TrackRenderState::Idle))
 				{
 					// We marked it successfully, so now we'll do the work
 					tracks[i]->Run(renderThreadNumFloatSamples);
@@ -206,7 +207,7 @@ namespace WaveSabrePlayerLib
 			}
 		}
 
-		if (!InterlockedDecrement(&renderThreadsRunning))
+		if (AtomicHelpers::XDec(&renderThreadsRunning) == 0)
 			SetEvent(renderDoneEvent);
 
 		return true;