add system.h for interfacing with system-level features

src/system.h

@@ -0,0 +1,63 @@
+#ifndef SYSTEM_H
+#define SYSTEM_H
+
+#include "common.h"
+
+class System {
+ public:
+  typedef int Status;
+
+  class Thread {
+   public:
+    virtual ~Thread() { }
+    virtual void run() = 0;
+  };
+
+  class Monitor {
+   public:
+    virtual ~Monitor() { }
+    virtual void acquire() = 0;
+    virtual void release() = 0;
+    virtual void wait() = 0;
+    virtual void notify() = 0;
+    virtual void notifyAll() = 0;
+    virtual void dispose() = 0;
+  };
+
+  class File {
+   public:
+    virtual ~File() { }
+    virtual Status read(uint8_t* data, unsigned* size) = 0;
+    virtual Status write(const uint8_t* data, unsigned size) = 0;
+    virtual Status close() = 0;
+  };
+
+  static const int ReadOnly = 00;
+  static const int WriteOnly = 01;
+  static const int ReadWrite = 02;
+  static const int Append = 02000;
+  static const int Create = 0100;
+
+  static const int UserRead = 0400;
+  static const int UserWrite = 0200;
+  static const int UserExecute = 0100;
+  static const int GroupRead = 040;
+  static const int GroupWrite = 020;
+  static const int GroupExecute = 010;
+  static const int OtherRead = 04;
+  static const int OtherWrite = 02;
+  static const int OtherExecute = 01;
+
+  virtual ~System() { }
+
+  virtual bool success(Status) = 0;
+  virtual void* allocate(unsigned size) = 0;
+  virtual void zero(void*, unsigned size) = 0;
+  virtual void free(void*) = 0;
+  virtual Status start(Thread*) = 0;
+  virtual Status make(Monitor**) = 0;
+  virtual Status open(File**, const char* path, int flags, int mode) = 0;
+  virtual void NO_RETURN abort() = 0;
+};
+
+#endif//SYSTEM_H