#include?
#include?
#include?“protocol.h“
#include?“datalink.h“
#define?inc（k）?if（k#define?DATA_TIMER??2800
#define?MAX_SEQ?7
#pragma?comment（lib“Protocol.lib“）

typedef?struct{?
????unsigned?char?kind;??????????//frame_DATA?
????unsigned?char?ack;			?//ACK?number
????unsigned?char?seq;			?//seq?bumber
????unsigned?char?data[PKT_LEN];?//傳輸數據?
????unsigned?int??padding;???????//CRC校驗和?
}frame;


static?unsigned?char?frame_nr?=?0buffer[MAX_SEQ+1][PKT_LEN]?nbuffered=0;
static?unsigned?char?frame_expected?=?0ack_expected=0next_frame_to_send=0;
static?int?phl_ready?=?0;


int?between（unsigned?char?aunsigned?char?bunsigned?char?c）	//判斷幀有沒有在當前窗口中
{
	if（（（a<=b）&&（b		return?1;
	else
		return?0;
}



static?void?put_frame（unsigned?char?*frame?int?len）
{
????*（unsigned?int?*）（frame?+?len）?=?crc32（frame?len）;
????send_frame（frame?len?+?4）;
????phl_ready?=?0;
}


static?void?send_data_frame（void）					//將幀傳遞給物理層傳送，并開始計時器計時
{
????frame?s;
	s.kind?=?frame_DATA;
	s.seq?=?next_frame_to_send;
	s.ack?=?（frame_expected+MAX_SEQ）%（MAX_SEQ+1）;
	memcpy（s.databuffer[next_frame_to_send]PKT_LEN）;
	dbg_frame（“Send?DATA?%d?%d?ID?%dwindows?%d\n“?s.seq?s.ack?*（short?*）s.datanbuffered）;
	put_frame（（unsigned?char?*）&s?3?+?PKT_LEN）;
????start_timer（next_frame_to_send?DATA_TIMER）;
	
}




int?main（int?argc?char?**argv）
{
????int?event?arg;
????frame?f;
????int?len?=?0;
	int?i;
????protocol_init（argc?argv）;?
????lprintf（“Designed?by?Su?Shihao?build:?“?__DATE__“??“__TIME__“\n“）;

????disable_network_layer（）;					//開始狀態，網絡層禁止遞交分組

????for?（;;）?{
????????event?=?wait_for_event（&arg）;
		switch?（event）?{
????????case?NETWORK_layer_READY:				//網絡層有分組要發送
			get_packet（buffer[next_frame_to_send]）;
				nbuffered++;
????????????send_data_frame（）;
			inc（next_frame_to_send）;
			break;

????????case?PHYSICAL_layer_READY:				//物理層準備
????????????phl_ready?=?1;
????????????break;

????????case?frame_RECEIVED:					//一個數據幀到達
????????????len?=?recv_frame（（unsigned?char?*）&f?sizeof?f）;
????????????if?（len?????????????????dbg_event（“****?Receiver?Error?Bad?CRC?Checksum\n“）;
				break;
			}//CRC校驗?
			
			if?（f.kind?==?frame_DATA）??
			{
				dbg_frame（“Recv?DATA?%d?%d?ID?%d\n“?f.seq?f.ack?*（short?*）f.data）;
				if?（f.seq?==?frame_expected）?//接收一幀?
				{
					put_packet（f.data?len?-?7）;
					inc（frame_expected）;
				}
				
				
				
				while（between（ack_expectedf.acknext_frame_to_send））//?檢查n-1，n-2等ack并確認
				{
					nbuffered=nbuffered-1;
					stop_timer（ack_expected）;
					inc（ack_expected）;
				}
			}
			
			break;?

????????case?DATA_TIMEOUT:						//TIMER超時，重傳發送窗口中所有幀
????????????dbg_event（“----?DATA?%d?timeout\n“?arg）;?
			next_frame_to_send=ack_expected;
			for（i=1;i<=nbuffered;i++）
			{
				send_data_frame（）;
				inc（next_frame_to_send）;
			}
????????????break;
????????}




????????if?（nbuffered????????????