BAdapterIO: Add initial seeking support

* This is by default provided using a relative buffer. When the
client request a seek over the range we currently have, we will
ask the backend with a SeekRequested. When the backend operation
ended successfully, the client is required to call SeekCompleted
before to return. This will cause the offset to change and the
buffer is cleaned as result. Next data received will be considered
to be at a position equal to the offset plus the relative position.

headers/private/media/AdapterIO.h

@@ -13,77 +13,82 @@
 
 
 class BAdapterIO;
+class RelativePositionIO;
 
 
 class BInputAdapter {
 public:
-	virtual	ssize_t			Write(const void* buffer, size_t size);
+	virtual	ssize_t					Write(const void* buffer, size_t size);
 
 private:
 	friend class BAdapterIO;
 
-							BInputAdapter(BAdapterIO* io);
-	virtual					~BInputAdapter();
+									BInputAdapter(BAdapterIO* io);
+	virtual							~BInputAdapter();
 
-			BAdapterIO*		fIO;
+			BAdapterIO*				fIO;
 
-	virtual	void			_ReservedInputAdapter1();
-	virtual void			_ReservedInputAdapter2();
+	virtual	void					_ReservedInputAdapter1();
+	virtual void					_ReservedInputAdapter2();
 
-			uint32			_reserved[2];
+			uint32					_reserved[2];
 };
 
 
 class BAdapterIO : public BMediaIO {
 public:
-							BAdapterIO(int32 flags,
-								bigtime_t timeout = B_INFINITE_TIMEOUT);
-	virtual					~BAdapterIO();
+									BAdapterIO(int32 flags,
+										bigtime_t timeout = B_INFINITE_TIMEOUT);
+	virtual							~BAdapterIO();
 
-	virtual void			GetFlags(int32* flags) const;
+	virtual void					GetFlags(int32* flags) const;
 
-	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	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	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;
+	virtual	status_t				SetSize(off_t size);
+	virtual	status_t				GetSize(off_t* size) const;
 
-			BInputAdapter*	BuildInputAdapter();
+			BInputAdapter*			BuildInputAdapter();
 
 protected:
 	friend class BInputAdapter;
 
-			void			SetBuffer(BPositionIO* io);
+			void					SetBuffer(BPositionIO* io);
 
-			ssize_t			BackWrite(const void* buffer, size_t size);
+			ssize_t					BackWrite(const void* buffer, size_t size);
+
+			status_t				SeekRequested(off_t position);
+			status_t				SeekCompleted(off_t position);
 
 private:
-			void			_WaitForData(size_t size);
+			status_t				_EvaluateWait(off_t position);
 
-			int32			fFlags;
-			bigtime_t		fTimeout;
+			int32					fFlags;
+			bigtime_t				fTimeout;
 
-			off_t			fBackPosition;
-	mutable RWLocker		fLock;
-			BPositionIO*	fBuffer;
+			off_t					fBackPosition;
+	mutable RWLocker				fLock;
 
-			BInputAdapter*	fInputAdapter;
+			RelativePositionIO*		fBuffer;
 
-							BAdapterIO(const BAdapterIO&);
-			BAdapterIO&		operator=(const BAdapterIO&);
+			BInputAdapter*			fInputAdapter;
 
-	virtual	void			_ReservedAdapterIO1();
-	virtual void			_ReservedAdapterIO2();
-	virtual void			_ReservedAdapterIO3();
-	virtual void			_ReservedAdapterIO4();
-	virtual void			_ReservedAdapterIO5();
+									BAdapterIO(const BAdapterIO&);
+			BAdapterIO&				operator=(const BAdapterIO&);
 
-			uint32			_reserved[5];
+	virtual	void					_ReservedAdapterIO1();
+	virtual void					_ReservedAdapterIO2();
+	virtual void					_ReservedAdapterIO3();
+	virtual void					_ReservedAdapterIO4();
+	virtual void					_ReservedAdapterIO5();
+
+			uint32					_reserved[5];
 };
 
 #endif	// _ADAPTER_IO_H