frameparser.cpp

来自「实现对文件的CRC校验」· C++ 代码 · 共 230 行

/******************************************************
      廖干洲
	  2120070266
	  第二次作业 Ethernet帧结构解析
       

***************************************************************/



#include<iomanip.h> 
#include<fstream.h>
#include<stdlib.h>
#define byte unsigned char

byte CheckCRC(byte *,int);                     //CRC校验函数

//****************************************************************************主函数开始


void main(int argc,char* argv[]){



   
 

    if(argc!=2)                                                     //检查输入格式   最好完善
	{
		cout<<"input error, please input it correctly"<<endl;
		exit(0);
	}


//----------------------------------------------------------------------打开文件的相关工作
	int l=0;                                                          //l存储字段长度
	ifstream fp;
	
	fp.open("input",ios::in|ios::binary|ios::nocreate);             //打开二进制读文件，且不创建不存在的文件
	
	if(!fp)                                                         //判断文件是否打开
	{
		cout<<"the file 'input' can not open."<<endl;
		exit(0);
	}
	else
		cout<<"the file 'input' is open !"<<endl;

	fp.seekg(0,ios::beg);
	
 //-----------------------------------------------------------------主循环输出每个帧
	
	
	int c;                                            //储存数据字节
	int k;                                                     
	int j;                                         //帧号
	for(j=1; (c=fp.get())!=EOF ; j++)        //判断文件结束
	{
		k=0;

		fp.seekg(-1,ios::cur);
		
		cout<<endl<<"帧号为:"<<j;             
		
 
		cout<<endl<<"前导码为:";                   //开始输出主要帧头
		cout<<setiosflags(ios::uppercase);           //显示大写字母
		for(int i=0;i<7;i++)
		cout<<hex<<fp.get()<<" ";
		
		
		cout<<endl<<"帧前定界符为:";
		for(;i<8;i++)
		cout<<hex<<fp.get()<<" ";
	

		byte * Data1 = new byte [14];         //存储目的地址，源地址，长度字段
	    
		cout<<endl<<"目的地址为:";
	    for(;i<14;i++,k++)
		{

		    c=fp.get();
			Data1[k] = c;
			if(c<16)
				cout<<"0";
			cout<<hex<<c;
		    if(i<13)
			    cout<<"-";
		}
    
	    cout<<endl<<"源地址为:";
	    for(k=6;i<20;i++,k++)
		{
		    c=fp.get();
			Data1[k] = c;
			if(c<16)
				cout<<"0";
			cout<<hex<<c;;
		    if(i<19)
			    cout<<"-";
		}

        cout<<endl<<"长度字段为:";
		
		c = fp.get();
		Data1[12] = c;
		if(c<16)
		    cout<<"0";
		cout<<hex<<c<<" ";

		l = c;
		c = fp.get();
		Data1[13] = c;
		if(c<16)
			cout<<"0";
		cout<<hex<<c;

		l <<= 8;					
		l |= c;

                                         
		if(l<46)
			l=46;                               //若数据字段小于46，则把46赋给l
		if(l>1500)                              //数据字段不能大于1500字节！
		{
			cout<<"Error!"<<endl;
			exit(0);
		}


	    cout<<endl;
		cout<<"LLC数据字段为:"<<endl;

		byte * Data2 = new byte [l];         //新建一个l长度的char型数组储存字段数据
        
  

		fp.read(Data2,l);                                     
		
		for(i=0;i<l;i++)       
		{
            cout<<Data2[i];
		}              
             

	    cout<<endl;

        l += 14; 

		byte * Data = new byte [l];
		
		for(i=0;i<14;i++)                                        //把需要校验的数都填入Data数组
			Data[i] = Data1[i];
		for(i=0;i<l-14;i++)
			Data[i+14] = Data2[i];

//------------------------------------------------------------------------CRC校验
 
		cout<<"CRC校验 ";

		byte cCorrect = CheckCRC(Data,l);                 //正确的CRC码

		if(cCorrect == fp.get())                                  //比较校验码真确与否
		{
            if(cCorrect < 16)
				cout<<'0';
			fp.seekg(-1,ios::cur);
			cout<<"（正确）:"<<hex<<fp.get();
			cout<<endl<<"状态:Accept";
		}
		else
		{
            if(cCorrect < 16)
				cout<<'0';
			fp.seekg(-1,ios::cur);
			cout<<"（错误）:"<<hex<<fp.get()<<" 应为:";
			cout<<hex<<(int)cCorrect;
			cout<<endl<<"状态:Discard";
		}

		cout<<endl;                                       //一个帧的解析结束

		 delete [] Data2;                                //释放内存
		 delete [] Data1;
		 delete [] Data;

	}

    cout<<endl<<"完毕"<<endl<<endl;
	fp.close();	
}


//********************************************************************** 主函数结束

//-------------------------------------------------------------------crc校验函数，用了查表法

byte  CheckCRC(byte *data, int len) 
{
      byte  crc = 0;    

      byte  CRC8_TABLE[256] = {
            0x00,0x07,0x0E,0x09,0x1C,0x1B,0x12,0x15,0x38,0x3F,0x36,0x31,0x24,0x23,0x2A,0x2D,
            0x70,0x77,0x7E,0x79,0x6C,0x6B,0x62,0x65,0x48,0x4F,0x46,0x41,0x54,0x53,0x5A,0x5D,
            0xE0,0xE7,0xEE,0xE9,0xFC,0xFB,0xF2,0xF5,0xD8,0xDF,0xD6,0xD1,0xC4,0xC3,0xCA,0xCD,
            0x90,0x97,0x9E,0x99,0x8C,0x8B,0x82,0x85,0xA8,0xAF,0xA6,0xA1,0xB4,0xB3,0xBA,0xBD,
            0xC7,0xC0,0xC9,0xCE,0xDB,0xDC,0xD5,0xD2,0xFF,0xF8,0xF1,0xF6,0xE3,0xE4,0xED,0xEA,
            0xB7,0xB0,0xB9,0xBE,0xAB,0xAC,0xA5,0xA2,0x8F,0x88,0x81,0x86,0x93,0x94,0x9D,0x9A,
            0x27,0x20,0x29,0x2E,0x3B,0x3C,0x35,0x32,0x1F,0x18,0x11,0x16,0x03,0x04,0x0D,0x0A,
            0x57,0x50,0x59,0x5E,0x4B,0x4C,0x45,0x42,0x6F,0x68,0x61,0x66,0x73,0x74,0x7D,0x7A,
            0x89,0x8E,0x87,0x80,0x95,0x92,0x9B,0x9C,0xB1,0xB6,0xBF,0xB8,0xAD,0xAA,0xA3,0xA4,
            0xF9,0xFE,0xF7,0xF0,0xE5,0xE2,0xEB,0xEC,0xC1,0xC6,0xCF,0xC8,0xDD,0xDA,0xD3,0xD4,
            0x69,0x6E,0x67,0x60,0x75,0x72,0x7B,0x7C,0x51,0x56,0x5F,0x58,0x4D,0x4A,0x43,0x44,
            0x19,0x1E,0x17,0x10,0x05,0x02,0x0B,0x0C,0x21,0x26,0x2F,0x28,0x3D,0x3A,0x33,0x34,
            0x4E,0x49,0x40,0x47,0x52,0x55,0x5C,0x5B,0x76,0x71,0x78,0x7F,0x6A,0x6D,0x64,0x63,
            0x3E,0x39,0x30,0x37,0x22,0x25,0x2C,0x2B,0x06,0x01,0x08,0x0F,0x1A,0x1D,0x14,0x13,
            0xAE,0xA9,0xA0,0xA7,0xB2,0xB5,0xBC,0xBB,0x96,0x91,0x98,0x9F,0x8A,0x8D,0x84,0x83,
            0xDE,0xD9,0xD0,0xD7,0xC2,0xC5,0xCC,0xCB,0xE6,0xE1,0xE8,0xEF,0xFA,0xFD,0xF4,0xF3
      };
        
      for (int i = 0; i < len; i++)
      {
         crc = CRC8_TABLE[(crc ^ data[i]) & 0xff];
      }
        
      return crc;
}

//---------------------------------------------------------------------------查表函数结束