/***GO-BACK-N協(xié)議，確認幀為捎帶確認***/

#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];?//凈荷域
????unsigned?int??padding;???????//存放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）;?