CRC 16 program

AquamaN · 04-12-2004, 09:48 PM

Ok everyone, I am trying to write a program do this:

-a C++ crcClass to implement the CRC-16 hardware bit shift mechanism.
-I want it to include appropriate member functions to compute crc, verify crc.
-Implement a driver that calls the above with a payload data (X bits where X need not be a multiple of 8) as would be done at transmit side, or payload and CRC (as would be done at receiver).
-The command line parameters include {tx or rx}, payloadFileName, crc value {if receive}

If anyone can help me, I would be grateful. Thanks a lot!

-AquamaN

Mohsen · 04-12-2004, 10:48 PM

I've read about the algorithm but do not implement one yet. Also I used a crc32 in NibelZoo packets. You can find that here.

AquamaN · 04-12-2004, 11:46 PM

Ok, thanks for your input. It helped. Now I am stuck on taking in a CRC value (like for example, 8EE9) from the command line, but I can not seem to do it. It's going to be argv[3] but I can not take it into the proper variable... Here is my code.

Code:

#include <iostream.h>
#include <stdlib.h>
#include <fstream.h>

typedef unsigned char Uchar;
typedef unsigned int Uint;


Uint crc_tbl0[] =
{
	0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
	0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
	0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
	0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
	0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
	0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
	0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
	0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
	0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
	0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
	0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
	0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
	0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
	0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
	0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
	0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
	0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
	0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
	0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
	0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
	0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
	0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
	0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
	0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
	0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
	0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
	0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
	0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
	0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
	0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
	0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
	0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040,
};

	/* Here's the lookup table for the nibble-at-a-time routine.
		Note that it's every 16th entry from the first table. The
		accompanying "crc_v3.txt" does a good job of explaining
		why this works. */

Uint crc_tbl1[] =
{

	0x0000, 0xCC01,	0xD801,	0x1400,	0xF001,	0x3C00,	0x2800,	0xE401,
	0xA001,	0x6C00,	0x7800,	0xB401,	0x5000,	0x9C01,	0x8801,	0x4400,
};

	/* Test case: generate the CRC of the specified file, using both the
		byte-at-a-time and nibble-at-a-time techniques. */

int main(int argc, char **argv)
{
	int ch;
	Uint acc0 = 0xFFFF, acc1 = 0xFFFF; //crcIn = 0xFFFF;
	Uchar crcIn;
	FILE *fp;
	bool Tx, Rx;

	if(argc > 1)
	{
		if(argv[1] == "Tx")
		{
			Tx = true;
			Rx = false;
		}
		else
		{
			Rx = true;
			Tx = false;
		}
		
		if((fp = fopen(argv[2], "rb")) == NULL)
		{
			cout << "Error opening file" << endl;
			exit(1);
		}
		
		crcIn = argv[3];  // <--- Take in right here!!!!

		while((ch = getc(fp)) != EOF)
		{
			acc0 = crc_tbl0[(Uchar) ch ^ (Uchar) acc0] ^ (Uchar) (acc0 >> 8);
			acc1 = crc_tbl1[(ch ^ acc1) & 15] ^ (acc1 >> 4);
			acc1 = crc_tbl1[((ch >> 4) ^ acc1) & 15] ^ (acc1 >> 4);
		}

		cout << "CRC checksum is: " << acc0 << "." << endl;
		
		if (Rx == true)
		{
			cout << "Currently in receiving mode..." << endl;
			cout << "Checking CRC for equality..." << endl;
			
		}
			
	}
	return 0;
}

I just need to take it in then compare it to acc0 further down the road for a CRC check... So, I obviously need to be able to compare two variables of the same type... (unless a cast operator is used). Thanks!

-AquamaN

AquamaN · 04-13-2004, 09:56 AM

Mohsen · 04-13-2004, 11:47 AM

Quote:

Now I am stuck on taking in a CRC value (like for example, 8EE9) from the command line, ...

You are trying to get some hex values in. Is it the problem? If yes, just use

Code:

long int strtol(const char *sptr, char **endptr, int base);

with approproate base (16) and NULL as the second argument.

AquamaN · 04-13-2004, 03:28 PM

You, sir, are AWESOME!! I can't believe I didn't think of that. Then again, that's why we have forums like this. Thanks a lot!!

-AquamaN