kernel: Divide Event into ReadableEvent and WritableEvent

More hardware accurate. On the actual system, there is a differentiation between the signaler and signalee, they form a client/server relationship much like ServerPort and ClientPort.

src/core/hle/kernel/readable_event.h

@@ -0,0 +1,56 @@
+// Copyright 2014 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "core/hle/kernel/object.h"
+#include "core/hle/kernel/wait_object.h"
+
+namespace Kernel {
+
+class KernelCore;
+class WritableEvent;
+
+class ReadableEvent final : public WaitObject {
+    friend class WritableEvent;
+
+public:
+    ~ReadableEvent() override;
+
+    std::string GetTypeName() const override {
+        return "ReadableEvent";
+    }
+    std::string GetName() const override {
+        return name;
+    }
+
+    static const HandleType HANDLE_TYPE = HandleType::Event;
+    HandleType GetHandleType() const override {
+        return HANDLE_TYPE;
+    }
+
+    bool ShouldWait(Thread* thread) const override;
+    void Acquire(Thread* thread) override;
+
+    void WakeupAllWaitingThreads() override;
+
+    void AddWaitingThread(SharedPtr<Thread> thread) override;
+    void RemoveWaitingThread(Thread* thread) override;
+
+    void Signal();
+    void Clear();
+
+    SharedPtr<WritableEvent> PromoteToWritable() const {
+        return writable_event;
+    }
+
+private:
+    explicit ReadableEvent(KernelCore& kernel);
+
+    SharedPtr<WritableEvent> writable_event; ///< WritableEvent associated with this ReadableEvent
+
+    std::string name; ///< Name of event (optional)
+};
+
+} // namespace Kernel