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Receive_Protocol_Handler Class Reference

Collaboration diagram for Receive_Protocol_Handler:

Detailed Description

This class receives the packets from the other end and performs the following operations:

• Check validity of the received packet
• Ask Transmit Protocol Handler to acknowledge the received packet
• Check if the remote end has acknowledged that was sent by Transmit Protocol Handler.
• Inform Transmit Protocol Handler about acknowledged packet.

See also:

Receive Protocol Handler Design Pattern

Definition at line 20 of file Receive_Protocol_Handler.h.

Public Member Functions
void	Handle_Received_Packet (Datagram *p_Packet)
	The Handle Receive Packet method completely handles the receive side processing of the protocol messages.
	Receive_Protocol_Handler (Protocol_Layer *p_Layer)
	The constructor for the class.
Private Attributes
int	m_next_Expected_Sequence_Number
	Transmit sequence number expected for the next packet.
int	m_last_Acknowledged_Sequence_Number
	Receive sequence number from the last packet.
Transmit_Protocol_Handler *	m_p_Transmit_Protocol_Handler
	Pointer to the associated Transmit Protocol Handler.
Protocol_Layer *	m_p_Layer
	Pointer to the parent layer. Used to obtain a pointer to the upper layer.

Constructor & Destructor Documentation

Receive_Protocol_Handler::Receive_Protocol_Handler (  Protocol_Layer *  p_Layer  )  [inline]

The constructor for the class. The constructor needs a pointer to the parent layer. The Receive Protocol Handler will use this pointer to obtain a pointer to to the upper layer. Parameters: p_Layer  Pointer to the parent layer. See also: Receive Protocol Handler Design Pattern Definition at line 107 of file Receive_Protocol_Handler.h. 00107 : 00108 m_p_Layer(p_Layer) 00109 { 00110 } };

Member Function Documentation

void Receive_Protocol_Handler::Handle_Received_Packet (  Datagram *  p_Packet  )  [inline]

The Handle Receive Packet method completely handles the receive side processing of the protocol messages. This method takes the following actions: Extract the header corresponding to this layer (See Protocol_Packet). Compare the packet's transmit sequence number with the expected sequence number. If the sequence number matches, take the following actions: Request Transmit Sequence Handler to acknowledge the just received packet. Add the message to the receive queue Modulo increment the next expected sequence number Compare the packet's receive sequence number with the last acknowledged sequence number. (Change in sequence number implies that an acknowledgement has been received from the other end). If a change is detected in the received sequence number, the following action is taken: Store the new receive sequence number as the last acknowledged sequence number. Inform the Transmit Protocol Handler about the acknowledgements received from the other end Parameters: p_Packet  Pointer to the packet passed by the lower layer. See also: Receive Protocol Handler Design Pattern Definition at line 58 of file Receive_Protocol_Handler.h. 00059 { 00060 // Extract the header needed by this layer 00061 p_Packet->Extract_Header(L2_HEADER_LENGTH); 00062 00063 // Compare the packet's transmit sequence number with 00064 // the expected sequence number 00065 if (p_Packet->Get_Transmit_Sequence_Number() == m_next_Expected_Sequence_Number) 00066 { 00067 // Request Transmit Sequence Handler to acknowledge 00068 // the just received packet 00069 m_p_Transmit_Protocol_Handler->Handle_Send_Ack_Request(m_next_Expected_Sequence_Number); 00070 00071 // Pass the message to the higher layer. The message is passed only if the upper layer 00072 // has been specified. 00073 Protocol_Layer *p_Upper_Layer = m_p_Layer->Get_Upper_Layer(); 00074 if (p_Upper_Layer) 00075 { 00076 p_Upper_Layer->Handle_Receive(p_Packet); 00077 } 00078 00079 // Modulo increment the next expected sequence number 00080 Modulo_Increment(m_next_Expected_Sequence_Number); 00081 } 00082 00083 // Compare the packet's receive sequence number with the 00084 // last acknowledged sequence number. (Change in sequence number 00085 // implies that an acknowledgement has been received from the other end) 00086 if (p_Packet->Get_Receive_Sequence_Number() != m_last_Acknowledged_Sequence_Number) 00087 { 00088 // Update the last acknowledged sequence number 00089 m_last_Acknowledged_Sequence_Number = p_Packet->Get_Receive_Sequence_Number(); 00090 00091 // Inform the Transmit Protocol Handler about the 00092 // acknowledgements received from the other end 00093 m_p_Transmit_Protocol_Handler->Handle_Received_Ack_Notification( 00094 m_last_Acknowledged_Sequence_Number); 00095 } 00096 }

Member Data Documentation

int Receive_Protocol_Handler::m_last_Acknowledged_Sequence_Number [private]

Receive sequence number from the last packet. Change in the receive sequence number means that the other end is acknowledging some packets Definition at line 30 of file Receive_Protocol_Handler.h.

• Receive_Protocol_Handler.h

Generated on Sun Feb 13 21:30:36 2005 for Object Oriented Design Examples by 1.3.4

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