Merge branch 'v0.22.x'

NEWS

@@ -7,8 +7,14 @@ ver 0.23 (not yet released)
   - snapcast: new plugin
 
 ver 0.22.7 (not yet released)
+* protocol
+  - don't use glibc extension to parse time stamps
 * decoder
   - ffmpeg: fix build problem with FFmpeg 3.4
+* storage
+  - curl: don't use glibc extension
+* output
+  - wasapi: add algorithm for finding usable audio format
 
 ver 0.22.6 (2021/02/16)
 * fix missing tags on songs in queue

doc/user.rst

@@ -141,6 +141,15 @@ Basically, there are two ways to compile :program:`MPD` for Windows:
 
 This section is about the latter.
 
+You need:
+
+* `mingw-w64 <http://mingw-w64.org/doku.php>`__
+* `Meson 0.49.0 <http://mesonbuild.com/>`__ and `Ninja
+  <https://ninja-build.org/>`__
+* cmake
+* pkg-config
+* quilt
+
 Just like with the native build, unpack the :program:`MPD` source
 tarball and change into the directory.  Then, instead of
 :program:`meson`, type:
@@ -168,6 +177,11 @@ You need:
 
 * Android SDK
 * `Android NDK r22 <https://developer.android.com/ndk/downloads>`_
+* `Meson 0.49.0 <http://mesonbuild.com/>`__ and `Ninja
+  <https://ninja-build.org/>`__
+* cmake
+* pkg-config
+* quilt
 
 Just like with the native build, unpack the :program:`MPD` source
 tarball and change into the directory.  Then, instead of

meson.build

@@ -261,7 +261,6 @@ sources = [
   'src/LogInit.cxx',
   'src/ls.cxx',
   'src/Instance.cxx',
-  'src/win32/Win32Main.cxx',
   'src/MusicBuffer.cxx',
   'src/MusicPipe.cxx',
   'src/MusicChunk.cxx',
@@ -309,6 +308,13 @@ sources = [
   'src/PlaylistFile.cxx',
 ]
 
+if is_windows
+  sources += [
+    'src/win32/Win32Main.cxx',
+    'src/win32/ComWorker.cxx',
+  ]
+endif
+
 if not is_android
   sources += [
     'src/CommandLine.cxx',

src/mixer/plugins/WasapiMixerPlugin.cxx

@@ -19,7 +19,7 @@
 
 #include "mixer/MixerInternal.hxx"
 #include "output/plugins/WasapiOutputPlugin.hxx"
-#include "win32/Com.hxx"
+#include "win32/ComWorker.hxx"
 #include "win32/HResult.hxx"
 
 #include <cmath>
@@ -28,92 +28,103 @@
 
 class WasapiMixer final : public Mixer {
 	WasapiOutput &output;
-	std::optional<COM> com;
 
 public:
 	WasapiMixer(WasapiOutput &_output, MixerListener &_listener)
 	: Mixer(wasapi_mixer_plugin, _listener), output(_output) {}
 
-	void Open() override { com.emplace(); }
+	void Open() override {}
 
-	void Close() noexcept override { com.reset(); }
+	void Close() noexcept override {}
 
 	int GetVolume() override {
-		HRESULT result;
-		float volume_level;
+		auto future = COMWorker::Async([&]() -> int {
+			HRESULT result;
+			float volume_level;
 
-		if (wasapi_is_exclusive(output)) {
-			ComPtr<IAudioEndpointVolume> endpoint_volume;
-			result = wasapi_output_get_device(output)->Activate(
-				__uuidof(IAudioEndpointVolume), CLSCTX_ALL, nullptr,
-				endpoint_volume.AddressCast());
-			if (FAILED(result)) {
-				throw FormatHResultError(
-					result, "Unable to get device endpoint volume");
+			if (wasapi_is_exclusive(output)) {
+				ComPtr<IAudioEndpointVolume> endpoint_volume;
+				result = wasapi_output_get_device(output)->Activate(
+					__uuidof(IAudioEndpointVolume), CLSCTX_ALL,
+					nullptr, endpoint_volume.AddressCast());
+				if (FAILED(result)) {
+					throw FormatHResultError(result,
+								 "Unable to get device "
+								 "endpoint volume");
+				}
+
+				result = endpoint_volume->GetMasterVolumeLevelScalar(
+					&volume_level);
+				if (FAILED(result)) {
+					throw FormatHResultError(result,
+								 "Unable to get master "
+								 "volume level");
+				}
+			} else {
+				ComPtr<ISimpleAudioVolume> session_volume;
+				result = wasapi_output_get_client(output)->GetService(
+					__uuidof(ISimpleAudioVolume),
+					session_volume.AddressCast<void>());
+				if (FAILED(result)) {
+					throw FormatHResultError(result,
+								 "Unable to get client "
+								 "session volume");
+				}
+
+				result = session_volume->GetMasterVolume(&volume_level);
+				if (FAILED(result)) {
+					throw FormatHResultError(
+						result, "Unable to get master volume");
+				}
 			}
 
-			result = endpoint_volume->GetMasterVolumeLevelScalar(
-				&volume_level);
-			if (FAILED(result)) {
-				throw FormatHResultError(
-					result, "Unable to get master volume level");
-			}
-		} else {
-			ComPtr<ISimpleAudioVolume> session_volume;
-			result = wasapi_output_get_client(output)->GetService(
-				__uuidof(ISimpleAudioVolume),
-				session_volume.AddressCast<void>());
-			if (FAILED(result)) {
-				throw FormatHResultError(
-					result, "Unable to get client session volume");
-			}
-
-			result = session_volume->GetMasterVolume(&volume_level);
-			if (FAILED(result)) {
-				throw FormatHResultError(result,
-							 "Unable to get master volume");
-			}
-		}
-
-		return std::lround(volume_level * 100.0f);
+			return std::lround(volume_level * 100.0f);
+		});
+		return future.get();
 	}
 
 	void SetVolume(unsigned volume) override {
-		HRESULT result;
-		const float volume_level = volume / 100.0f;
+		COMWorker::Async([&]() {
+			HRESULT result;
+			const float volume_level = volume / 100.0f;
 
-		if (wasapi_is_exclusive(output)) {
-			ComPtr<IAudioEndpointVolume> endpoint_volume;
-			result = wasapi_output_get_device(output)->Activate(
-				__uuidof(IAudioEndpointVolume), CLSCTX_ALL, nullptr,
-				endpoint_volume.AddressCast());
-			if (FAILED(result)) {
-				throw FormatHResultError(
-					result, "Unable to get device endpoint volume");
-			}
+			if (wasapi_is_exclusive(output)) {
+				ComPtr<IAudioEndpointVolume> endpoint_volume;
+				result = wasapi_output_get_device(output)->Activate(
+					__uuidof(IAudioEndpointVolume), CLSCTX_ALL,
+					nullptr, endpoint_volume.AddressCast());
+				if (FAILED(result)) {
+					throw FormatHResultError(
+						result,
+						"Unable to get device endpoint volume");
+				}
 
-			result = endpoint_volume->SetMasterVolumeLevelScalar(volume_level,
-									     nullptr);
-			if (FAILED(result)) {
-				throw FormatHResultError(
-					result, "Unable to set master volume level");
-			}
-		} else {
-			ComPtr<ISimpleAudioVolume> session_volume;
-			result = wasapi_output_get_client(output)->GetService(
-				__uuidof(ISimpleAudioVolume),
-				session_volume.AddressCast<void>());
-			if (FAILED(result)) {
-				throw FormatHResultError(
-					result, "Unable to get client session volume");
-			}
+				result = endpoint_volume->SetMasterVolumeLevelScalar(
+					volume_level, nullptr);
+				if (FAILED(result)) {
+					throw FormatHResultError(
+						result,
+						"Unable to set master volume level");
+				}
+			} else {
+				ComPtr<ISimpleAudioVolume> session_volume;
+				result = wasapi_output_get_client(output)->GetService(
+					__uuidof(ISimpleAudioVolume),
+					session_volume.AddressCast<void>());
+				if (FAILED(result)) {
+					throw FormatHResultError(
+						result,
+						"Unable to get client session volume");
+				}
 
-			result = session_volume->SetMasterVolume(volume_level, nullptr);
-			if (FAILED(result)) {
-				throw FormatHResultError(result,
-							 "Unable to set master volume");
+				result = session_volume->SetMasterVolume(volume_level,
+									 nullptr);
+				if (FAILED(result)) {
+					throw FormatHResultError(
+						result, "Unable to set master volume");
+				}
 			}
-		}
+		}).get();
 	}
 };
 

src/storage/plugins/CurlStorage.cxx

@@ -193,7 +193,7 @@ ParseTimeStamp(const char *s)
 {
 	try {
 		// TODO: make this more robust
-		return ParseTimePoint(s, "%a, %d %b %Y %T %Z");
+		return ParseTimePoint(s, "%a, %d %b %Y %T");
 	} catch (...) {
 		return std::chrono::system_clock::time_point::min();
 	}

src/thread/Future.hxx

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2020-2021 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef THREAD_FUTURE_HXX
+#define THREAD_FUTURE_HXX
+
+#ifdef _WIN32
+
+#include "WindowsFuture.hxx"
+
+template <typename R>
+using Future = WinFuture<R>;
+template <typename R>
+using Promise = WinPromise<R>;
+
+#else
+
+#include <future>
+
+template <typename R>
+using Future = std::future<R>;
+template <typename R>
+using Promise = std::promise<R>;
+
+#endif
+
+#endif

src/thread/WindowsFuture.hxx

@@ -0,0 +1,394 @@
+/*
+ * Copyright 2020-2021 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef THREAD_WINDOWS_FUTURE_HXX
+#define THREAD_WINDOWS_FUTURE_HXX
+
+#include "CriticalSection.hxx"
+#include "WindowsCond.hxx"
+#include <atomic>
+#include <memory>
+#include <variant>
+
+enum class WinFutureErrc : int {
+	future_already_retrieved = 1,
+	promise_already_satisfied,
+	no_state,
+	broken_promise,
+};
+
+enum class WinFutureStatus { ready, timeout, deferred };
+
+static inline const std::error_category &win_future_category() noexcept;
+class WinFutureCategory : public std::error_category {
+public:
+	const char *name() const noexcept override { return "win_future"; }
+	std::string message(int Errcode) const override {
+		using namespace std::literals;
+		switch (static_cast<WinFutureErrc>(Errcode)) {
+		case WinFutureErrc::broken_promise:
+			return "Broken promise"s;
+		case WinFutureErrc::future_already_retrieved:
+			return "Future already retrieved"s;
+		case WinFutureErrc::promise_already_satisfied:
+			return "Promise already satisfied"s;
+		case WinFutureErrc::no_state:
+			return "No associated state"s;
+		default:
+			return "Unknown error"s;
+		}
+	}
+	std::error_condition default_error_condition(int code) const noexcept override {
+		return std::error_condition(code, win_future_category());
+	}
+};
+static inline const std::error_category &win_future_category() noexcept {
+	static const WinFutureCategory win_future_category_instance{};
+	return win_future_category_instance;
+}
+
+class WinFutureError : public std::logic_error {
+public:
+	WinFutureError(WinFutureErrc errcode)
+	: WinFutureError(
+		  std::error_code(static_cast<int>(errcode), win_future_category())) {}
+
+private:
+	explicit WinFutureError(std::error_code errcode)
+	: std::logic_error("WinFutureError: " + errcode.message()), code(errcode) {}
+	std::error_code code;
+};
+
+template <typename T>
+class WinFutureState {
+private:
+	mutable CriticalSection mutex;
+	WindowsCond condition;
+	std::variant<std::monostate, T, std::exception_ptr> result;
+	bool retrieved = false;
+	bool ready = false;
+
+public:
+	bool is_ready() const noexcept {
+		std::unique_lock<CriticalSection> lock(mutex);
+		return ready;
+	}
+
+	bool already_retrieved() const noexcept {
+		std::unique_lock<CriticalSection> lock(mutex);
+		return retrieved;
+	}
+
+	void wait() {
+		std::unique_lock<CriticalSection> lock(mutex);
+		condition.wait(lock, [this]() { return ready; });
+	}
+
+	template <class Rep, class Period>
+	WinFutureStatus
+	wait_for(const std::chrono::duration<Rep, Period> &timeout_duration) const {
+		std::unique_lock<CriticalSection> lock(mutex);
+		// deferred function not support yet
+		if (condition.wait_for(lock, timeout_duration,
+				       [this]() { return ready; })) {
+			return WinFutureStatus::ready;
+		}
+		return WinFutureStatus::timeout;
+	}
+
+	virtual T &get_value() {
+		std::unique_lock<CriticalSection> lock(mutex);
+		if (retrieved) {
+			throw WinFutureError(WinFutureErrc::future_already_retrieved);
+		}
+		if (auto eptr = std::get_if<std::exception_ptr>(&result)) {
+			std::rethrow_exception(*eptr);
+		}
+		retrieved = true;
+		condition.wait(lock, [this]() { return ready; });
+		if (auto eptr = std::get_if<std::exception_ptr>(&result)) {
+			std::rethrow_exception(*eptr);
+		}
+		return *std::get_if<T>(&result);
+	}
+
+	void set_value(const T &value) {
+		std::unique_lock<CriticalSection> lock(mutex);
+		if (!std::holds_alternative<std::monostate>(&result)) {
+			throw WinFutureError(WinFutureErrc::promise_already_satisfied);
+		}
+		result.template emplace<T>(value);
+		ready = true;
+		condition.notify_all();
+	}
+
+	void set_value(T &&value) {
+		std::unique_lock<CriticalSection> lock(mutex);
+		if (!std::holds_alternative<std::monostate>(result)) {
+			throw WinFutureError(WinFutureErrc::promise_already_satisfied);
+		}
+		result.template emplace<T>(std::move(value));
+		ready = true;
+		condition.notify_all();
+	}
+
+	void set_exception(std::exception_ptr eptr) {
+		std::unique_lock<CriticalSection> lock(mutex);
+		if (!std::holds_alternative<std::monostate>(result)) {
+			throw WinFutureError(WinFutureErrc::promise_already_satisfied);
+		}
+		result.template emplace<std::exception_ptr>(eptr);
+		ready = true;
+		condition.notify_all();
+	}
+};
+
+template <typename T>
+class WinFutureStateManager {
+public:
+	WinFutureStateManager() = default;
+	WinFutureStateManager(std::shared_ptr<WinFutureState<T>> new_state)
+	: state(std::move(new_state)) {}
+	WinFutureStateManager(const WinFutureStateManager &) = default;
+	WinFutureStateManager &operator=(const WinFutureStateManager &) = default;
+	WinFutureStateManager(WinFutureStateManager &&) = default;
+	WinFutureStateManager &operator=(WinFutureStateManager &&) = default;
+
+	[[nodiscard]] bool valid() const noexcept { return static_cast<bool>(state); }
+
+	void wait() const {
+		if (!valid()) {
+			throw WinFutureError(WinFutureErrc::no_state);
+		}
+		state->wait();
+	}
+
+	template <class Rep, class Period>
+	WinFutureStatus
+	wait_for(const std::chrono::duration<Rep, Period> &timeout_duration) const {
+		if (!valid()) {
+			throw WinFutureError(WinFutureErrc::no_state);
+		}
+		return state->wait_for(timeout_duration);
+	}
+
+	T &get_value() const {
+		if (!valid()) {
+			throw WinFutureError(WinFutureErrc::no_state);
+		}
+		return state->get_value();
+	}
+
+	void set_value(const T &value) {
+		if (!valid()) {
+			throw WinFutureError(WinFutureErrc::no_state);
+		}
+		state->set_value(value);
+	}
+
+	void set_value(T &&value) {
+		if (!valid()) {
+			throw WinFutureError(WinFutureErrc::no_state);
+		}
+		state->set_value(std::move(value));
+	}
+
+	void set_exception(std::exception_ptr eptr) {
+		if (!valid()) {
+			throw WinFutureError(WinFutureErrc::no_state);
+		}
+		state->set_exception(eptr);
+	}
+
+private:
+	std::shared_ptr<WinFutureState<T>> state;
+};
+
+template <typename T>
+class WinFuture : public WinFutureStateManager<T> {
+	using Base = WinFutureStateManager<T>;
+	static_assert(!std::is_array_v<T> && std::is_object_v<T> &&
+			      std::is_destructible_v<T>,
+		      "T in future<T> must meet the Cpp17Destructible requirements "
+		      "(N4878 [futures.unique.future]/4).");
+
+public:
+	WinFuture() noexcept = default;
+	WinFuture(WinFuture &&) noexcept = default;
+	WinFuture &operator=(WinFuture &&) noexcept = default;
+	WinFuture(const WinFuture &) noexcept = delete;
+	WinFuture &operator=(const WinFuture &) noexcept = delete;
+
+	WinFuture(const Base &base, std::monostate) : Base(base) {}
+	~WinFuture() noexcept = default;
+	T get() {
+		WinFuture local(std::move(*this));
+		return std::move(local.get_value());
+	}
+
+private:
+	using Base::get_value;
+	using Base::set_exception;
+	using Base::set_value;
+};
+
+template <typename T>
+class WinFuture<T &> : public WinFutureStateManager<T *> {
+	using Base = WinFutureStateManager<T *>;
+
+public:
+	WinFuture() noexcept = default;
+	WinFuture(WinFuture &&) noexcept = default;
+	WinFuture &operator=(WinFuture &&) noexcept = default;
+	WinFuture(const WinFuture &) noexcept = delete;
+	WinFuture &operator=(const WinFuture &) noexcept = delete;
+
+	WinFuture(const Base &base, std::monostate) : Base(base) {}
+	~WinFuture() noexcept = default;
+	T &get() {
+		WinFuture local(std::move(*this));
+		return *local.get_value();
+	}
+
+private:
+	using Base::get_value;
+	using Base::set_exception;
+	using Base::set_value;
+};
+
+template <>
+class WinFuture<void> : public WinFutureStateManager<int> {
+	using Base = WinFutureStateManager<int>;
+
+public:
+	WinFuture() noexcept = default;
+	WinFuture(WinFuture &&) noexcept = default;
+	WinFuture &operator=(WinFuture &&) noexcept = default;
+	WinFuture(const WinFuture &) noexcept = delete;
+	WinFuture &operator=(const WinFuture &) noexcept = delete;
+
+	WinFuture(const Base &base, std::monostate) : Base(base) {}
+	~WinFuture() noexcept = default;
+	void get() {
+		WinFuture local(std::move(*this));
+		local.get_value();
+	}
+
+private:
+	using Base::get_value;
+	using Base::set_exception;
+	using Base::set_value;
+};
+
+template <typename T>
+class WinPromiseBase {
+public:
+	WinPromiseBase(std::shared_ptr<WinFutureState<T>> new_state)
+	: state(std::move(new_state)) {}
+	WinPromiseBase(WinPromiseBase &&) = default;
+	WinPromiseBase &operator=(WinPromiseBase &&) = default;
+	WinPromiseBase(const WinPromiseBase &) = delete;
+	WinPromiseBase &operator=(const WinPromiseBase &) = delete;
+
+	WinFutureStateManager<T> &get_state_for_set() {
+		if (!state.valid()) {
+			throw WinFutureError(WinFutureErrc::no_state);
+		}
+		return state;
+	}
+
+	WinFutureStateManager<T> &get_state_for_future() {
+		if (!state.valid()) {
+			throw WinFutureError(WinFutureErrc::no_state);
+		}
+		if (future_retrieved) {
+			throw WinFutureError(WinFutureErrc::future_already_retrieved);
+		}
+		future_retrieved = true;
+		return state;
+	}
+
+private:
+	WinFutureStateManager<T> state;
+	bool future_retrieved = false;
+};
+
+template <typename T>
+class WinPromise {
+public:
+	WinPromise() : base(std::make_shared<WinFutureState<T>>()) {}
+	WinPromise(WinPromise &&) = default;
+	WinPromise(const WinPromise &) = delete;
+	~WinPromise() noexcept {}
+	[[nodiscard]] WinFuture<T> get_future() {
+		return WinFuture<T>(base.get_state_for_future(), std::monostate());
+	}
+	void set_value(const T &value) { base.get_state_for_set().set_value(value); }
+	void set_value(T &&value) {
+		base.get_state_for_set().set_value(std::forward<T>(value));
+	}
+	void set_exception(std::exception_ptr eptr) {
+		base.get_state_for_set().set_exception(eptr);
+	}
+
+private:
+	WinPromiseBase<T> base;
+};
+
+template <typename T>
+class WinPromise<T &> {
+public:
+	WinPromise() : base(std::make_shared<WinFutureState<T *>>()) {}
+	WinPromise(WinPromise &&) = default;
+	WinPromise(const WinPromise &) = delete;
+	~WinPromise() noexcept {}
+	[[nodiscard]] WinFuture<T &> get_future() {
+		return WinFuture<T>(base.get_state_for_future(), std::monostate());
+	}
+	void set_value(T &value) {
+		base.get_state_for_set().set_value(std::addressof(value));
+	}
+	void set_exception(std::exception_ptr eptr) {
+		base.get_state_for_set().set_exception(eptr);
+	}
+
+private:
+	WinPromiseBase<T *> base;
+};
+
+template <>
+class WinPromise<void> {
+public:
+	WinPromise() : base(std::make_shared<WinFutureState<int>>()) {}
+	WinPromise(WinPromise &&) = default;
+	WinPromise(const WinPromise &) = delete;
+	~WinPromise() noexcept {}
+	[[nodiscard]] WinFuture<void> get_future() {
+		return WinFuture<void>(base.get_state_for_future(), std::monostate());
+	}
+	void set_value() { base.get_state_for_set().set_value(0); }
+	void set_exception(std::exception_ptr eptr) {
+		base.get_state_for_set().set_exception(eptr);
+	}
+
+private:
+	WinPromiseBase<int> base;
+};
+
+#endif

src/time/ISO8601.cxx

@@ -202,7 +202,7 @@ ParseISO8601(const char *s)
 	}
 
 	/* parse the date */
-	const char *end = strptime(s, "%F", &tm);
+	const char *end = strptime(s, "%Y-%m-%d", &tm);
 	if (end == nullptr) {
 		/* try without field separators */
 		end = strptime(s, "%Y%m%d", &tm);

src/win32/Com.hxx

@@ -29,9 +29,19 @@
 class COM {
 public:
 	COM() {
-		HRESULT result = CoInitializeEx(nullptr, COINIT_MULTITHREADED);
-		if (FAILED(result)) {
-			throw FormatHResultError(result, "Unable to initialize COM");
+		if (HRESULT result = CoInitializeEx(nullptr, COINIT_MULTITHREADED);
+		    FAILED(result)) {
+			throw FormatHResultError(
+				result,
+				"Unable to initialize COM with COINIT_MULTITHREADED");
+		}
+	}
+	COM(bool) {
+		if (HRESULT result = CoInitializeEx(nullptr, COINIT_APARTMENTTHREADED);
+		    FAILED(result)) {
+			throw FormatHResultError(
+				result,
+				"Unable to initialize COM with COINIT_APARTMENTTHREADED");
 		}
 	}
 	~COM() noexcept { CoUninitialize(); }

src/win32/ComWorker.cxx

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2020 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+#include "ComWorker.hxx"
+#include "Log.hxx"
+#include "thread/Name.hxx"
+#include "util/Domain.hxx"
+#include "win32/Com.hxx"
+
+namespace {
+static constexpr Domain com_worker_domain("com_worker");
+}
+
+Mutex COMWorker::mutex;
+unsigned int COMWorker::reference_count = 0;
+std::optional<COMWorker::COMWorkerThread> COMWorker::thread;
+
+void COMWorker::COMWorkerThread::Work() noexcept {
+	FormatDebug(com_worker_domain, "Working thread started");
+	SetThreadName("COM Worker");
+	COM com{true};
+	while (true) {
+		if (!running_flag.test_and_set()) {
+			FormatDebug(com_worker_domain, "Working thread ended");
+			return;
+		}
+		while (!spsc_buffer.empty()) {
+			std::function<void()> function;
+			spsc_buffer.pop(function);
+			function();
+		}
+		event.Wait(200);
+	}
+}

src/win32/ComWorker.hxx

@@ -0,0 +1,110 @@
+/*
+ * Copyright 2020 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_WIN32_COM_WORKER_HXX
+#define MPD_WIN32_COM_WORKER_HXX
+
+#include <boost/lockfree/spsc_queue.hpp>
+#include <condition_variable>
+#include <mutex>
+#include <optional>
+
+#include "thread/Future.hxx"
+#include "thread/Mutex.hxx"
+#include "thread/Thread.hxx"
+#include "win32/WinEvent.hxx"
+#include <objbase.h>
+#include <windows.h>
+
+// Worker thread for all COM operation
+class COMWorker {
+private:
+	class COMWorkerThread : public Thread {
+	public:
+		COMWorkerThread() : Thread{BIND_THIS_METHOD(Work)} {}
+
+	private:
+		friend class COMWorker;
+		void Work() noexcept;
+		void Finish() noexcept {
+			running_flag.clear();
+			event.Set();
+		}
+		void Push(const std::function<void()> &function) {
+			spsc_buffer.push(function);
+			event.Set();
+		}
+
+		boost::lockfree::spsc_queue<std::function<void()>> spsc_buffer{32};
+		std::atomic_flag running_flag = true;
+		WinEvent event{};
+	};
+
+public:
+	static void Aquire() {
+		std::unique_lock locker(mutex);
+		if (reference_count == 0) {
+			thread.emplace();
+			thread->Start();
+		}
+		++reference_count;
+	}
+	static void Release() noexcept {
+		std::unique_lock locker(mutex);
+		--reference_count;
+		if (reference_count == 0) {
+			thread->Finish();
+			thread->Join();
+			thread.reset();
+		}
+	}
+
+	template <typename Function, typename... Args>
+	static auto Async(Function &&function, Args &&...args) {
+		using R = std::invoke_result_t<std::decay_t<Function>,
+					       std::decay_t<Args>...>;
+		auto promise = std::make_shared<Promise<R>>();
+		auto future = promise->get_future();
+		thread->Push([function = std::forward<Function>(function),
+			      args = std::make_tuple(std::forward<Args>(args)...),
+			      promise = std::move(promise)]() mutable {
+			try {
+				if constexpr (std::is_void_v<R>) {
+					std::apply(std::forward<Function>(function),
+						   std::move(args));
+					promise->set_value();
+				} else {
+					promise->set_value(std::apply(
+						std::forward<Function>(function),
+						std::move(args)));
+				}
+			} catch (...) {
+				promise->set_exception(std::current_exception());
+			}
+		});
+		return future;
+	}
+
+private:
+	static Mutex mutex;
+	static unsigned int reference_count;
+	static std::optional<COMWorkerThread> thread;
+};
+
+#endif

src/win32/Win32Main.cxx

@@ -18,9 +18,6 @@
  */
 
 #include "Main.hxx"
-
-#ifdef _WIN32
-
 #include "util/Compiler.h"
 #include "Instance.hxx"
 #include "system/FatalError.hxx"
@@ -155,5 +152,3 @@ void win32_app_stopping()
 	else
 		running.store(false);
 }
-
-#endif