Import all this stuff into a single repo called Serenity.

AK/MappedFile.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include "String.h"
+
+namespace AK {
+
+class MappedFile {
+public:
+    MappedFile() { }
+    explicit MappedFile(String&& fileName);
+    MappedFile(MappedFile&&);
+    ~MappedFile();
+
+    bool isValid() const { return m_map != (void*)-1; }
+
+    void* pointer() { return m_map; }
+    const void* pointer() const { return m_map; }
+    size_t fileLength() const { return m_fileLength; }
+
+private:
+    String m_fileName;
+    size_t m_fileLength { 0 };
+    int m_fd { -1 };
+    void* m_map { (void*)-1 };
+};
+
+}
+
+using AK::MappedFile;
+