Add private class BFdIO

Simple BPositionIO implementation using the POSIX API on a FD. In effect
similar to BFile, but more easily ported to kernel and boot loader (and
the FD is reusable).

headers/build/private/storage/FdIO.h

@@ -0,0 +1 @@
+#include <../private/storage/FdIO.h>

headers/private/storage/FdIO.h

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2014, Ingo Weinhold, [email protected].
+ * Distributed under the terms of the MIT License.
+ */
+#ifndef _FD_IO_H_
+#define _FD_IO_H_
+
+
+#include <DataIO.h>
+
+
+class BFdIO : public BPositionIO {
+public:
+								BFdIO();
+								BFdIO(int fd, bool keepFd);
+	virtual						~BFdIO();
+
+			void				SetTo(int fd, bool keepFd);
+			void				Unset();
+
+	virtual	ssize_t				Read(void* buffer, size_t size);
+	virtual	ssize_t				Write(const void* buffer, size_t size);
+
+	virtual	ssize_t				ReadAt(off_t position, void* buffer,
+									size_t size);
+	virtual	ssize_t				WriteAt(off_t position, const void* buffer,
+									size_t size);
+
+	virtual	off_t				Seek(off_t position, uint32 seekMode);
+	virtual	off_t				Position() const;
+
+	virtual	status_t			SetSize(off_t size);
+	virtual	status_t			GetSize(off_t* _size) const;
+
+private:
+								BFdIO(const BFdIO& other);
+			BFdIO&				operator=(const BFdIO& other);
+
+private:
+			int					fFd;
+			bool				fOwnsFd;
+};
+
+
+#endif	// _FD_IO_H_