256ecc_30.c

The following source code shows an example for generating of 3bytes per 256bytes, based on hamming c

/*******************************************************************/
/* Revision History						   */
/* Revision 2.1 was revised for speed-up			   */
/* Revision 3.0 was revised for speed-up			   */
/* Description : The following source code shows an example for    */
/* generating of 3bytes per 256bytes, based on hamming code ecc    */ 
/*******************************************************************/

typedef unsigned int uint;
typedef unsigned char uchar;

void 	main()
{
	uint i, j;
	uchar	ecc_gen[3],write_data[256],paritr[256], tmp = 0, tmp2=0;
	uchar   data_table0[16] = {0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0};
	uchar   data_table1[16] = {1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1};
	uchar   sum=0,paritc = 0;
	uchar	parit0c = 0, parit1c = 0, parit2c = 0, parit3c = 0;
	uchar	parit4c = 0, parit5c = 0, parit6c = 0, parit7c = 0;
	uchar	parit1_1, parit1_2, parit2_1, parit2_2, parit4_1, parit4_2;
	uchar	parit8_1 = 0, parit8_2 = 0, parit16_1 = 0, parit16_2 = 0, parit32_1 = 0, parit32_2 = 0;
	uchar	parit64_1 = 0, parit64_2 = 0, parit128_1 = 0, parit128_2 = 0, parit256_1 = 0, parit256_2 = 0;
	uchar	parit512_1 = 0, parit512_2 = 0, parit1024_1 = 0, parit1024_2 = 0;

	for( i = 0; i < 256; i++)
	{
		paritc = paritc ^ (*(write_data+i));

		tmp = (*(write_data+i) & 0xf0) >> 4;
		tmp2 = *(write_data+i) & 0x0f;
		switch(tmp)
		{
			case 0:
				*(paritr + i) = *(data_table0 + tmp2);
				break;
			case 1:
				*(paritr + i) = *(data_table1 + tmp2);
				break;
			case 2:
				*(paritr + i) = *(data_table1 + tmp2);
				break;
			case 3:
				*(paritr + i) = *(data_table0 + tmp2);
				break;
			case 4:
				*(paritr + i) = *(data_table1 + tmp2);
				break;
			case 5:
				*(paritr + i) = *(data_table0 + tmp2);
				break;
			case 6:
				*(paritr + i) = *(data_table0 + tmp2);
				break;
			case 7:
				*(paritr + i) = *(data_table1 + tmp2);
				break;
			case 8:
				*(paritr + i) = *(data_table1 + tmp2);
				break;
			case 9:
				*(paritr + i) = *(data_table0 + tmp2);
				break;
			case 10:
				*(paritr + i) = *(data_table0 + tmp2);
				break;
			case 11:
				*(paritr + i) = *(data_table1 + tmp2);
				break;
			case 12:
				*(paritr + i) = *(data_table0 + tmp2);
				break;
			case 13:
				*(paritr + i) = *(data_table1 + tmp2);
				break;
			case 14:
				*(paritr + i) = *(data_table1 + tmp2);
				break;
			case 15:
				*(paritr + i) = *(data_table0 + tmp2);
				break;
		}

	}

	parit0c = ((paritc & 0x01) ? 1 : 0);
	parit1c = ((paritc & 0x02) ? 1 : 0);
	parit2c = ((paritc & 0x04) ? 1 : 0);
	parit3c = ((paritc & 0x08) ? 1 : 0);
	parit4c = ((paritc & 0x10) ? 1 : 0);
	parit5c = ((paritc & 0x20) ? 1 : 0);
	parit6c = ((paritc & 0x40) ? 1 : 0);
	parit7c = ((paritc & 0x80) ? 1 : 0);

	parit1_2 = parit6c ^ parit4c ^ parit2c ^ parit0c;
	parit1_1 = parit7c ^ parit5c ^ parit3c ^ parit1c;
	parit2_2 = parit5c ^ parit4c ^ parit1c ^ parit0c;
	parit2_1 = parit7c ^ parit6c ^ parit3c ^ parit2c;
	parit4_2 = parit3c ^ parit2c ^ parit1c ^ parit0c;
	parit4_1 = parit7c ^ parit6c ^ parit5c ^ parit4c;

	for( i = 0 ; i < 256;i++)	sum=sum ^ (*(paritr+i));

	for ( i = 0; i < 256; i = i+2 )
		parit8_2 = parit8_2 ^ (*(paritr + i));
	for ( i = 0; i < 256; i = i+4 )
	{
		parit16_2 = parit16_2 ^ (*(paritr + i));
		parit16_2 = parit16_2 ^ (*(paritr + i + 1));
	}
	for ( i = 0; i < 256; i = i+8 )
	{
		for ( j = 0; j <= 3; j++ )
			parit32_2 = parit32_2 ^ (*(paritr + i + j));
	}
	for ( i = 0; i < 256; i = i+16 )
	{
		for ( j = 0; j <= 7; j++ )
			parit64_2 = parit64_2 ^ (*(paritr + i + j));
	}
	for ( i = 0; i < 256; i = i+32 )
	{
		for ( j = 0; j <= 15; j++ )
			parit128_2 = parit128_2 ^ (*(paritr + i + j));
	}
	for ( i = 0; i < 256; i = i+64 )
	{
		for ( j = 0; j <= 31; j++ )
			parit256_2 = parit256_2 ^ (*(paritr + i + j));
	}
	for ( i = 0; i < 256; i = i+128 )
	{
		for ( j = 0; j <= 63; j++ )
			parit512_2 = parit512_2 ^ (*(paritr + i + j));
	}
	for ( i = 0; i < 256; i = i+256 )
	{
		for ( j = 0; j <= 127; j++ )
			parit1024_2 = parit1024_2 ^ (*(paritr + i + j));
	}

	if(sum==0){
		parit1024_1=parit1024_2;
		parit512_1=parit512_2;
		parit256_1=parit256_2;
		parit128_1=parit128_2;
		parit64_1=parit64_2;
		parit32_1=parit32_2;
		parit16_1=parit16_2;
		parit8_1=parit8_2;
	}
	else{
		parit1024_1 = (parit1024_2 ? 0 : 1);
		parit512_1  = (parit512_2  ? 0 : 1);
		parit256_1  = (parit256_2  ? 0 : 1);
		parit128_1  = (parit128_2  ? 0 : 1);
		parit64_1   = (parit64_2   ? 0 : 1);
		parit32_1   = (parit32_2   ? 0 : 1);
		parit16_1   = (parit16_2   ? 0 : 1);
		parit8_1    = (parit8_2    ? 0 : 1);
	}

	parit1_2 <<= 2;
	parit1_1 <<= 3;
	parit2_2 <<= 4;
	parit2_1 <<= 5;
	parit4_2 <<= 6;
	parit4_1 <<= 7;
	parit128_1 <<= 1;
	parit256_2 <<= 2;
	parit256_1 <<= 3;
	parit512_2 <<= 4;
	parit512_1 <<= 5;
	parit1024_2 <<= 6;
	parit1024_1 <<= 7;
	parit8_1 <<= 1;
	parit16_2 <<= 2;

	parit16_1 <<= 3;
	parit32_2 <<= 4;
	parit32_1 <<= 5;
	parit64_2 <<= 6;
	parit64_1 <<= 7;

	*(ecc_gen + 0) = ~( parit64_1|parit64_2|parit32_1|parit32_2|parit16_1|parit16_2|parit8_1|parit8_2 );
	*(ecc_gen + 1) = ~( parit1024_1|parit1024_2|parit512_1|parit512_2|parit256_1|parit256_2|parit128_1|parit128_2 );
	*(ecc_gen + 2) = ~( parit4_1|parit4_2|parit2_1|parit2_2|parit1_1|parit1_2|0x00|0x00 );
}