gen_crc32_table.c

根据不同的生成多项

#include <stdio.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>


#define CRC32POLY 0xedb88320
#define CRC32POLY_REV 0x04c11db7
#define FCSTABLE crc32_table

#define FCS(crcnum, c) (((crcnum) << 8) ^ FCSTABLE[(((crcnum) >> 8) ^ (c)) & 0xff])
#define FCS_REV(crcnum, c) (((crcnum) >> 8) ^ FCSTABLE[((crcnum) ^ (c)) & 0xff])

#define REVERSE 1 

unsigned int crc32_table[256];

unsigned long int Reflect(unsigned long int ref, char ch)
{

	unsigned long int value = 0;

	int i;

	// 交换bit0和bit7，bit1和bit6，类推

	for(i = 1; i < (ch + 1); i++)

	{

		if(ref & 1)

		value |= 1 << (ch - i);

		ref >>= 1;

	}

	return value;

}


init_crc32_table(unsigned int *crc32_table, const unsigned int ulPolynomial)
{

	unsigned long int crc,temp;

	int i,j;

	// 256个值

	for(i = 0; i <= 0xFF; i++)
	{

		temp=Reflect(i, 8);

		crc32_table[i]= temp<< 24;

		for (j = 0; j < 8; j++)

		{

			unsigned long int t1,t2;

			unsigned long int flag=crc32_table[i]&0x80000000;

			t1=(crc32_table[i] << 1);

			if(flag==0)

				t2=0;

			else

				t2=ulPolynomial;

			crc32_table[i] =t1^t2 ;

		}

		crc=crc32_table[i];

		crc32_table[i] = Reflect(crc32_table[i], 32);

	}
/*
	
	for(i=0; i<0xff; i++)
	{
		temp = (i << 24) & 0xff000000;
		
		crc32_table[i] = 0;
		
		for(j=0; j<8; j++)
		{
			if( (temp ^ crc32_table[i]) & 0x80000000)

				crc32_table[i] = (crc32_table[i] << 1) ^ ulPolynomial;
			else
				crc32_table[i] <<= 1;
			
			temp <<= 1;

		}

	}
*/

}



unsigned int Trid_CRC32_Gen(unsigned char *buf, int len)
{
	unsigned int i = 0;

	unsigned int crc32 = 0xFFFFFFFF;
	
	//unsigned int crc32 = 0x00000000;

	unsigned char *pD, c;

	pD = buf;

/*
	for(i=0; i<len; i++)
	{

		crc32=crc32_table[(crc32^(*(pD+i)))&0xff] ^ (crc32>>8);

	}

	return ~crc32;

*/

	while(len--)
	{
		c = pD[i++]; 
#if REVERSE
		crc32 = FCS_REV(crc32, c);
#else
		crc32 = FCS(crc32, c);
#endif
	}

		
#if REVERSE
	return ~crc32;
	//return crc32;
#else
	return crc32;
#endif
	
}



void main()
{
	int i;
	unsigned char data = 0x10;
	unsigned char j=0;
	//int fd;

	//fd = open("table.txt", O_CREAT | O_RDWR);
	//if(fd == -1)
	//{
	//	printf("open file error!!\n");
	//	exit(-1);
	//}

	FILE *fp;

	fp = fopen("table.txt", "w+");

	if(fp == NULL)
	{
		printf("error\n");
		exit(-1);
	}

	init_crc32_table(crc32_table, CRC32POLY_REV);
	
	for(i=0; i<256; i++)
	{
		//fprintf(fp, "0x%x, ", crc32_table[i]);
		printf("0x%08x ", crc32_table[i]);
		
		if((i % 8) == 7)
			//fprintf(fp, "\n");
			printf("\n");
	}

	printf("\n\n0x%08x\n\n", Trid_CRC32_Gen(&data, 1));

	for(i=0; i<256; i++)
	{
		printf("0x%08x ", Trid_CRC32_Gen(&j, 1));
		
		if((i%8) == 7)
			printf("\n");
		j++;
	}
	
	fclose(fp);

}