add kqueue io_backend for macOS and BSD systems

CMakeLists.txt

@@ -8,6 +8,7 @@ option(NETKIT_ENABLE_FALLBACK_CA "Enable fallback CA certficate (required for De
 option(NETKIT_ENABLE_SOCK_CUSTOM_RESOLVER "Enable using netkit's DNS resolver instead of the system resolver" OFF)
 option(NETKIT_ENABLE_EPOLL "Enable using epoll backend (Linux only)" ON)
 option(NETKIT_ENABLE_WSAPOLL "Enable using wsapoll backend (Windows only)" ON)
+option(NETKIT_ENABLE_KQUEUE "Enable using kqueue backend (macOS, BSD only)" ON)
 option(NETKIT_ENABLE_HTTP "Enable netkit's HTTP abstractions" ON)
 option(NETKIT_ENABLE_DNS "Enable netkit's DNS features" ON)
 option(NETKIT_WOLFSSL_DEBUG "Enable WolfSSL debugging" OFF)
@@ -75,6 +76,7 @@ add_library(netkit ${NETKIT_LIB_TYPE}
         src/body/multipart_part_body.cpp
         src/io/io_awaitable.cpp
         src/io/linux/io_backend.cpp
+        src/io/bsd/io_backend.cpp
         src/socket/native/native_async_socket.cpp
         src/socket/native/native_sync_listener.cpp
         src/socket/native/native_async_listener.cpp
@@ -215,6 +217,10 @@ if (NETKIT_ENABLE_WSAPOLL)
     target_compile_definitions(netkit PUBLIC NETKIT_WSAPOLL)
 endif()
 
+if (NETKIT_ENABLE_KQUEUE)
+    target_compile_definitions(netkit PUBLIC NETKIT_KQUEUE)
+endif()
+
 if (WIN32)
     add_definitions(-DNOMINMAX)
 endif()

include/netkit/definitions.hpp

@@ -32,6 +32,12 @@
 #define NETKIT_LINUX 1
 #endif
 
+#if !defined(NETKIT_LINUX) && \
+	defined(NETKIT_UNIX) && !defined(NETKIT_DKP) && \
+	!defined(NETKIT_MACOS)
+#define NETKIT_BSD
+#endif
+
 #ifndef NETKIT_FALLBACK_IPV4_DNS_1
 #define NETKIT_FALLBACK_IPV4_DNS_1 "8.8.8.8"
 #endif

include/netkit/io/bsd/io_backend.hpp

@@ -0,0 +1,53 @@
+#pragma once
+
+#include <netkit/definitions.hpp>
+#include <unordered_set>
+
+#if (defined(NETKIT_MACOS) || defined(NETKIT_BSD)) \
+	&& defined(NETKIT_KQUEUE)
+
+#include <netkit/io/basic_io_backend.hpp>
+
+#include <coroutine>
+#include <unordered_map>
+#include <sys/event.h>
+
+namespace netkit::io {
+
+class io_backend : public basic_io_backend {
+public:
+	io_backend();
+	~io_backend() override;
+
+	void wake() override;
+
+	void update_state(
+		io_handle_t fd,
+		const io_handle_state& state
+	) override;
+
+	void register_waiter(
+		io_handle_t fd,
+		io_event ev,
+		std::coroutine_handle<> h
+	) override;
+
+	void run() override;
+	void stop() override;
+
+	void poll(int timeout_ms) override;
+	void poll() override;
+
+private:
+	static constexpr uintptr_t wake_ident = 1;
+
+	io_handle_t kqueue_fd_ = -1;
+	bool running_ = true;
+
+	std::unordered_map<io_handle_t, io_handle_state> fd_map_;
+	std::unordered_set<io_handle_t> registered_fds_;
+};
+
+} // namespace netkit::io
+
+#endif

include/netkit/io/fallback/io_backend.hpp

@@ -5,6 +5,8 @@
 
 #if !defined(NETKIT_LINUX) || !defined(NETKIT_EPOLL)
 #if !defined(NETKIT_WINDOWS) || !defined(NETKIT_WSAPOLL)
+#if !defined(NETKIT_BSD) || !defined(NETKIT_KQUEUE)
+#if !defined(NETKIT_MACOS) || !defined(NETKIT_KQUEUE)
 
 #include <atomic>
 #include <condition_variable>
@@ -54,5 +56,7 @@ class NETKIT_API io_backend : public basic_io_backend {
 
 } // namespace netkit::io
 
+#endif
+#endif
 #endif
 #endif

include/netkit/io/io_backend.hpp

@@ -2,4 +2,5 @@
 
 #include <netkit/io/fallback/io_backend.hpp>
 #include <netkit/io/linux/io_backend.hpp>
-#include <netkit/io/windows/io_backend.hpp>
+#include <netkit/io/windows/io_backend.hpp>
+#include <netkit/io/bsd/io_backend.hpp>

include/netkit/netkit.hpp

@@ -85,6 +85,7 @@
 #include <netkit/io/linux/io_backend.hpp>
 #include <netkit/io/fallback/io_backend.hpp>
 #include <netkit/io/windows/io_backend.hpp>
+#include <netkit/io/bsd/io_backend.hpp>
 #include <netkit/io/io_backend.hpp>
 #include <netkit/io/io_awaitable.hpp>
 #include <netkit/io/io_context.hpp>