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Protocol_Layer Class Reference

Inheritance diagram for Protocol_Layer:

Detailed Description

This class defines the common interface for interactions between different layers of a protocol. This has several advantages:

• The implementation of one layer is completely decoupled from the other layers. The implementers of one layer do not even need to include the header files defining the other layers.
• Layers can be added and removed without needing any changes to the code for individual layers. (e.g. an IPSec layer can be added between the IP and Physical layers, without making any changes to the IP or the Physical Layer code).
• A single layer could interface with multiple upper or lower layer protocols using the same interface. (e.g. an IP layer implementation could interface with an ATM or Ethernet physical layer. No changes would be needed to the code for the IP layer.

Note that this transparent layered design is possible because the Protocol_Packet class directly supports addition and removal of layer specific protocol headers and trailers without allocating new buffers at every layer boundary.

See also:

Protocol Layer Design Pattern

Definition at line 32 of file Protocol_Layer.h.

Public Member Functions
	Protocol_Layer ()
	Create a protocol layer object.
virtual void	Transmit (Protocol_Packet *p_Packet)=0
	Process and transmit the packet passed by higher layer.
virtual void	Handle_Receive (Protocol_Packet *p_Packet)=0
	Receive and process the packets passed by a lower layer.
void	Set_Upper_Layer (Protocol_Layer *p_Layer)
	Set the upper protocol layer.
void	Set_Lower_Layer (Protocol_Layer *p_Layer)
	Set the lower protocol layer.
Protocol_Layer *	Get_Upper_Layer () const
	Get the upper protocol layer.
Protocol_Layer *	Get_Lower_Layer () const
	Get the lower protocol layer.
Private Attributes
Protocol_Layer *	m_p_Lower_Layer
	Pointer to the lower layer.
Protocol_Layer *	m_p_Upper_Layer
	Pointer to the lower layer.

Constructor & Destructor Documentation

Protocol_Layer::Protocol_Layer (   )  [inline]

Create a protocol layer object. The lower and upper protocol layers are defaulted to NULL value. See also: Protocol Layer Design Pattern Definition at line 52 of file Protocol_Layer.h. 00053 { 00054 m_p_Lower_Layer = NULL; 00055 m_p_Upper_Layer = NULL; 00056 }

Member Function Documentation

virtual void Protocol_Layer::Transmit (  Protocol_Packet *  p_Packet  )  [pure virtual]

Process and transmit the packet passed by higher layer. The packets are passed to the lower layer. This is a pure virtual function. All inheriting classes must implement this method. Parameters: p_Packet  Pointer to the packet received from the upper layer. See also: Protocol Layer Design Pattern Implemented in Datalink_Layer.

virtual void Protocol_Layer::Handle_Receive (  Protocol_Packet *  p_Packet  )  [pure virtual]

Receive and process the packets passed by a lower layer. After processing, the packet will be passed to the upper layer. This is a pure virtual function. All inheriting classes must implement this method. Parameters: p_Packet  Pointer to the packet received from the lower layer. See also: Protocol Layer Design Pattern Implemented in Datalink_Layer.

void Protocol_Layer::Set_Upper_Layer (  Protocol_Layer *  p_Layer  )  [inline]

Set the upper protocol layer. Messages received from the lower layer will be passed to this layer for upper layer handling. Parameters: p_Layer  Pointer to the upper layer for this layer. See also: Protocol Layer Design Pattern Definition at line 85 of file Protocol_Layer.h. 00086 { m_p_Upper_Layer = p_Layer; }

void Protocol_Layer::Set_Lower_Layer (  Protocol_Layer *  p_Layer  )  [inline]

Set the lower protocol layer. Messages received from the upper layer will be passed to this layer for lower layer handling. Parameters: p_Layer  Pointer to the lower layer for this layer. See also: Protocol Layer Design Pattern Definition at line 96 of file Protocol_Layer.h. 00097 { m_p_Lower_Layer = p_Layer; }

Protocol_Layer* Protocol_Layer::Get_Upper_Layer (   )  const [inline]

Get the upper protocol layer. Messages received from the lower layer will be passed to this layer for upper layer handling. Return values: Protocol_Layer  Pointer to the upper layer. See also: Protocol Layer Design Pattern Definition at line 107 of file Protocol_Layer.h. 00108 { return m_p_Upper_Layer; }

Protocol_Layer* Protocol_Layer::Get_Lower_Layer (   )  const [inline]

Get the lower protocol layer. Messages received from the upper layer will be passed to this layer for lower layer handling. Return values: Protocol_Layer  Pointer to the lower layer. See also: Protocol Layer Design Pattern Definition at line 118 of file Protocol_Layer.h. 00119 { return m_p_Lower_Layer; }

Member Data Documentation

Protocol_Layer* Protocol_Layer::m_p_Lower_Layer [private]

Pointer to the lower layer. Initialized by Set_Lower_Layer method. This pointers can change dynamically as protocol layers are added and deleted. Thus the pointer value should always be obtained from the Layer object just before sending the message. Definition at line 38 of file Protocol_Layer.h.

Protocol_Layer* Protocol_Layer::m_p_Upper_Layer [private]

Pointer to the lower layer. Initialized by the Set_Upper_Layer method. This pointers can change dynamically as protocol layers are added and deleted. Thus the pointer value should always be obtained from the Layer object just before sending the message. Definition at line 44 of file Protocol_Layer.h.

• Protocol_Layer.h

Generated on Sun Feb 13 21:30:34 2005 for Object Oriented Design Examples by 1.3.4

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