♻️ Implement std's Lockable for SDL mutex wrapper

Rather than rolling our own lock guard, implement the requirements for
using `std::lock_guard` et al and use that.

Source/sound.cpp

@@ -8,6 +8,7 @@
 #include <cstdint>
 #include <list>
 #include <memory>
+#include <mutex>
 
 #include <aulib.h>
 #include <Aulib/DecoderDrwav.h>
@@ -69,7 +70,7 @@ void CleanupMusic()
 }
 
 std::list<std::unique_ptr<SoundSample>> duplicateSounds;
-SDLMutexUniquePtr duplicateSoundsMutex;
+std::optional<SdlMutex> duplicateSoundsMutex;
 
 SoundSample *DuplicateSound(const SoundSample &sound)
 {
@@ -79,13 +80,13 @@ SoundSample *DuplicateSound(const SoundSample &sound)
 	auto *result = duplicate.get();
 	decltype(duplicateSounds.begin()) it;
 	{
-		SDLMutexLockGuard lock(duplicateSoundsMutex.get());
+		const std::lock_guard<SdlMutex> lock(*duplicateSoundsMutex);
 		duplicateSounds.push_back(std::move(duplicate));
 		it = duplicateSounds.end();
 		--it;
 	}
 	result->SetFinishCallback([it]([[maybe_unused]] Aulib::Stream &stream) {
-		SDLMutexLockGuard lock(duplicateSoundsMutex.get());
+		const std::lock_guard<SdlMutex> lock(*duplicateSoundsMutex);
 		duplicateSounds.erase(it);
 	});
 	return result;
@@ -129,7 +130,7 @@ static int CapVolume(int volume)
 
 void ClearDuplicateSounds()
 {
-	SDLMutexLockGuard lock(duplicateSoundsMutex.get());
+	const std::lock_guard<SdlMutex> lock(*duplicateSoundsMutex);
 	duplicateSounds.clear();
 }
 
@@ -214,7 +215,7 @@ void snd_init()
 	LogVerbose(LogCategory::Audio, "Aulib sampleRate={} channels={} frameSize={} format={:#x}",
 	    Aulib::sampleRate(), Aulib::channelCount(), Aulib::frameSize(), Aulib::sampleFormat());
 
-	duplicateSoundsMutex = SDLMutexUniquePtr { SDL_CreateMutex() };
+	duplicateSoundsMutex.emplace();
 	gbSndInited = true;
 }
 
@@ -222,7 +223,7 @@ void snd_deinit()
 {
 	if (gbSndInited) {
 		Aulib::quit();
-		duplicateSoundsMutex = nullptr;
+		duplicateSoundsMutex = std::nullopt;
 	}
 
 	gbSndInited = false;

Source/storm/storm.cpp

@@ -4,6 +4,7 @@
 #include <SDL_endian.h>
 #include <cstddef>
 #include <cstdint>
+#include <mutex>
 #include <string>
 
 #include "Radon.hpp"
@@ -34,19 +35,19 @@ namespace {
 bool directFileAccess = false;
 std::string *SBasePath = nullptr;
 
-} // namespace
+SdlMutex Mutex;
 
-SDL_mutex *Mutex = SDL_CreateMutex();
+} // namespace
 
 bool SFileReadFileThreadSafe(HANDLE hFile, void *buffer, DWORD nNumberOfBytesToRead, DWORD *read, int *lpDistanceToMoveHigh)
 {
-	SDLMutexLockGuard lock(Mutex);
+	const std::lock_guard<SdlMutex> lock(Mutex);
 	return SFileReadFile(hFile, buffer, nNumberOfBytesToRead, read, lpDistanceToMoveHigh);
 }
 
 bool SFileCloseFileThreadSafe(HANDLE hFile)
 {
-	SDLMutexLockGuard lock(Mutex);
+	const std::lock_guard<SdlMutex> lock(Mutex);
 	return SFileCloseFile(hFile);
 }
 

Source/utils/push_aulib_decoder.cpp

@@ -3,6 +3,7 @@
 #include <algorithm>
 #include <cstring>
 #include <limits>
+#include <mutex>
 
 #include <aulib.h>
 
@@ -17,7 +18,7 @@ void PushAulibDecoder::PushSamples(const std::int16_t *data, unsigned size) noex
 	std::memcpy(item.data.get(), data, size * sizeof(data[0]));
 	item.len = size;
 	item.pos = item.data.get();
-	SDLMutexLockGuard lock(queue_mutex_.get());
+	const std::lock_guard<SdlMutex> lock(queue_mutex_);
 	queue_.push(std::move(item));
 }
 
@@ -31,13 +32,13 @@ void PushAulibDecoder::PushSamples(const std::uint8_t *data, unsigned size) noex
 		item.data[i] = static_cast<std::int16_t>((data[i] - Center) * Scale);
 	item.len = size;
 	item.pos = item.data.get();
-	SDLMutexLockGuard lock(queue_mutex_.get());
+	const std::lock_guard<SdlMutex> lock(queue_mutex_);
 	queue_.push(std::move(item));
 }
 
 void PushAulibDecoder::DiscardPendingSamples() noexcept
 {
-	SDLMutexLockGuard lock(queue_mutex_.get());
+	const std::lock_guard<SdlMutex> lock(queue_mutex_);
 	queue_ = std::queue<AudioQueueItem>();
 }
 
@@ -75,7 +76,7 @@ int PushAulibDecoder::doDecoding(float buf[], int len, bool &callAgain)
 
 	unsigned remaining = len;
 	{
-		SDLMutexLockGuard lock(queue_mutex_.get());
+		const std::lock_guard<SdlMutex> lock(queue_mutex_);
 		AudioQueueItem *item;
 		while ((item = Next()) != nullptr) {
 			if (static_cast<unsigned>(remaining) <= item->len) {

Source/utils/push_aulib_decoder.h

@@ -20,7 +20,6 @@ public:
 	PushAulibDecoder(int numChannels, int sampleRate)
 	    : numChannels_(numChannels)
 	    , sampleRate_(sampleRate)
-	    , queue_mutex_(SDL_CreateMutex())
 	{
 	}
 
@@ -61,7 +60,7 @@ private:
 	AudioQueueItem *Next();
 
 	std::queue<AudioQueueItem> queue_;
-	SDLMutexUniquePtr queue_mutex_;
+	SdlMutex queue_mutex_;
 };
 
 } // namespace devilution

Source/utils/sdl_mutex.h

@@ -3,38 +3,47 @@
 #include <memory>
 
 #include <SDL_mutex.h>
+#include <SDL_version.h>
 
 namespace devilution {
 
-/**
- * @brief Deletes the SDL mutex using `SDL_DestroyMutex`.
+/*
+ * RAII wrapper for SDL_mutex. Satisfies std's "Lockable" (SDL 2) or "BasicLockable" (SDL 1)
+ * requirements so it can be used with std::lock_guard and friends.
  */
-struct SDLMutexDeleter {
-	void operator()(SDL_mutex *mutex) const
+class SdlMutex final {
+public:
+	SdlMutex()
+	    : mutex_(SDL_CreateMutex())
 	{
-		SDL_DestroyMutex(mutex);
 	}
-};
 
-using SDLMutexUniquePtr = std::unique_ptr<SDL_mutex, SDLMutexDeleter>;
+	~SdlMutex()
+	{
+		SDL_DestroyMutex(mutex_);
+	}
 
-struct SDLMutexLockGuard {
-public:
-	explicit SDLMutexLockGuard(SDL_mutex *mutex)
-	    : mutex_(mutex)
+	SdlMutex(const SdlMutex &) = delete;
+	SdlMutex(SdlMutex &&) = delete;
+	SdlMutex &operator=(const SdlMutex &) = delete;
+	SdlMutex &operator=(SdlMutex &&) = delete;
+
+	void lock() noexcept // NOLINT(readability-identifier-naming)
 	{
 		SDL_LockMutex(mutex_);
 	}
 
-	~SDLMutexLockGuard()
+#if SDL_VERSION_ATLEAST(2, 0, 0)
+	bool try_lock() noexcept // NOLINT(readability-identifier-naming)
 	{
-		SDL_UnlockMutex(mutex_);
+		return SDL_TryLockMutex(mutex_) == 0;
 	}
+#endif
 
-	SDLMutexLockGuard(const SDLMutexLockGuard &) = delete;
-	SDLMutexLockGuard(SDLMutexLockGuard &&) = delete;
-	SDLMutexLockGuard &operator=(const SDLMutexLockGuard &) = delete;
-	SDLMutexLockGuard &operator=(SDLMutexLockGuard &&) = delete;
+	void unlock() noexcept // NOLINT(readability-identifier-naming)
+	{
+		SDL_UnlockMutex(mutex_);
+	}
 
 private:
 	SDL_mutex *mutex_;