📄 ecc.c
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/*+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Module Name: ECC.C
Abstract: Error Correcting Codes (ECC) module for FLASH Media Drivers
under Windows CE 3.0 (and later). Unfortunately, some types
of FLASH media (i.e. NAND flash) do not necessarily guarantee
data integrity due to the electrical characteristics of the
media. As a result, it is often necessary to use ECC to detect
erroneous data and (hopefully) correct it.
Notes: This code is based on the ECC algorithm publicly available on
Samsung's FLASH media website.
-----------------------------------------------------------------------------*/
#include "ecc.h"
/*++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Function: ECC_ComputeECC()
Description: Computes the error correcting code for the specified data.
Notes: The following implementation uses a Hammming Code to compute
3 bytes of ECC information for every 256 bytes of data. It is
the caller's responsibility to insure the input buffers meet this
constraint...
Returns: Boolean indicating success.
-------------------------------------------------------------------------------*/
BOOL ECC_ComputeECC(LPBYTE pData, DWORD dwDataBuffLen, LPBYTE pECC, DWORD dwECCBuffLen)
{
static UINT i, j, k;
static UCHAR evenParity[16] = {0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0}; // Look-up table (LUT)
static UCHAR dataXOR = 0;
static UCHAR bit0, bit1, bit2, bit3, bit4, bit5, bit6, bit7;
// Column parity terms. NOTE: p subscript denotes "prime" (i.e. P1p = P1')
static UCHAR P1, P2, P4, P1p, P2p, P4p;
// Row parity terms. NOTE: p subscript denotes "prime" (i.e. P8p = P8')
UCHAR P8, P8p, P16, P16p, P32, P32p, P64, P64p, P128, P128p,
P256, P256p, P512, P512p, P1024, P1024p;
//----- 1. Check to make sure the input buffers are legitimate... -----
if((pData == NULL) || (pECC == NULL) || (dwDataBuffLen < DATA_BLOCK_LEN) || (dwECCBuffLen < ECC_BUFF_LEN) )
{
DEBUGMSG(1, (TEXT("FMD:ECC_ComputeECC() - Input buffers are not legitimate!\r\n")));
return FALSE;
}
//----- 2. Segregrate the data buffer into 256 byte blocks and compute ECC info for each block -----
for(j=0,k=0; j<dwDataBuffLen; j+= DATA_BLOCK_LEN)
{
//----- 3. Initialize the ROW parity terms -----
dataXOR = 0;
P8=0; P8p=0; P16=0; P16p=0; P32=0; P32p=0; P64=0; P64p=0;
P128=0; P128p=0; P256=0; P256p=0; P512=0; P512p=0; P1024=0; P1024p=0;
//----- 4. Compute the ROW parity terms P8, P8p, P16, ... P1024p -----
// NOTE: For speedup purposes, the otherwise 9 separate loops are unrolled into 3 large loops...
for(i=j; i<j+DATA_BLOCK_LEN; i+=32)
{
P8p ^= pData[i] ^ pData[i+2] ^ pData[i+4] ^ pData[i+6] ^ pData[i+8] ^ pData[i+10] ^ pData[i+12] ^ pData[i+14]
^ pData[i+16] ^ pData[i+18] ^ pData[i+20] ^ pData[i+22] ^ pData[i+24] ^ pData[i+26] ^ pData[i+28] ^ pData[i+30];
P8 ^= pData[i+1] ^ pData[i+3] ^ pData[i+5] ^ pData[i+7] ^ pData[i+9] ^ pData[i+11] ^ pData[i+13] ^ pData[i+15]
^ pData[i+17] ^ pData[i+19] ^ pData[i+21] ^ pData[i+23] ^ pData[i+25] ^ pData[i+27] ^ pData[i+29] ^ pData[i+31];
P16p ^= pData[i] ^ pData[i+1] ^ pData[i+4] ^ pData[i+5] ^ pData[i+8] ^ pData[i+9] ^ pData[i+12] ^ pData[i+13]
^ pData[i+16] ^ pData[i+17] ^ pData[i+20] ^ pData[i+21] ^ pData[i+24] ^ pData[i+25] ^ pData[i+28] ^ pData[i+29];
P16 ^= pData[i+2] ^ pData[i+3] ^ pData[i+6] ^ pData[i+7] ^ pData[i+10] ^ pData[i+11] ^ pData[i+14] ^ pData[i+15]
^ pData[i+18] ^ pData[i+19] ^ pData[i+22] ^ pData[i+23] ^ pData[i+26] ^ pData[i+27] ^ pData[i+30] ^ pData[i+31];
P32p ^= pData[i] ^ pData[i+1] ^ pData[i+2] ^ pData[i+3] ^ pData[i+8] ^ pData[i+9] ^ pData[i+10] ^ pData[i+11]
^ pData[i+16] ^ pData[i+17] ^ pData[i+18] ^ pData[i+19] ^ pData[i+24] ^ pData[i+25] ^ pData[i+26] ^ pData[i+27];
P32 ^= pData[i+4] ^ pData[i+5] ^ pData[i+6] ^ pData[i+7] ^ pData[i+12] ^ pData[i+13] ^ pData[i+14] ^ pData[i+15]
^ pData[i+20] ^ pData[i+21] ^ pData[i+22] ^ pData[i+23] ^ pData[i+28] ^ pData[i+29] ^ pData[i+30] ^ pData[i+31];
P64p ^= pData[i] ^ pData[i+1] ^ pData[i+2] ^ pData[i+3] ^ pData[i+4] ^ pData[i+5] ^ pData[i+6] ^ pData[i+7]
^ pData[i+16] ^ pData[i+17] ^ pData[i+18] ^ pData[i+19] ^ pData[i+20] ^ pData[i+21] ^ pData[i+22] ^ pData[i+23];
P64 ^= pData[i+8] ^ pData[i+9] ^ pData[i+10] ^ pData[i+11] ^ pData[i+12] ^ pData[i+13] ^ pData[i+14] ^ pData[i+15]
^ pData[i+24] ^ pData[i+25] ^ pData[i+26] ^ pData[i+27] ^ pData[i+28] ^ pData[i+29] ^ pData[i+30] ^ pData[i+31];
P128p ^= pData[i] ^ pData[i+1] ^ pData[i+2] ^ pData[i+3] ^ pData[i+4] ^ pData[i+5] ^ pData[i+6] ^ pData[i+7]
^ pData[i+8] ^ pData[i+9] ^ pData[i+10] ^ pData[i+11] ^ pData[i+12] ^ pData[i+13] ^ pData[i+14] ^ pData[i+15];
P128 ^= pData[i+16] ^ pData[i+17] ^ pData[i+18] ^ pData[i+19] ^ pData[i+20] ^ pData[i+21] ^ pData[i+22] ^ pData[i+23]
^ pData[i+24] ^ pData[i+25] ^ pData[i+26] ^ pData[i+27] ^ pData[i+28] ^ pData[i+29] ^ pData[i+30] ^ pData[i+31];
}
P8p = evenParity[((P8p & 0xF0) >> 4)] ^ evenParity[(P8p & 0x0F)];
P8 = evenParity[((P8 & 0xF0) >> 4)] ^ evenParity[(P8 & 0x0F)];
P16p = evenParity[((P16p & 0xF0) >> 4)] ^ evenParity[(P16p & 0x0F)];
P16 = evenParity[((P16 & 0xF0) >> 4)] ^ evenParity[(P16 & 0x0F)];
P32p = evenParity[((P32p & 0xF0) >> 4)] ^ evenParity[(P32p & 0x0F)];
P32 = evenParity[((P32 & 0xF0) >> 4)] ^ evenParity[(P32 & 0x0F)];
P64p = evenParity[((P64p & 0xF0) >> 4)] ^ evenParity[(P64p & 0x0F)];
P64 = evenParity[((P64 & 0xF0) >> 4)] ^ evenParity[(P64 & 0x0F)];
P128p = evenParity[((P128p & 0xF0) >> 4)] ^ evenParity[(P128p & 0x0F)];
P128 = evenParity[((P128 & 0xF0) >> 4)] ^ evenParity[(P128 & 0x0F)];
for(i=j; i<j+DATA_BLOCK_LEN; i+=128)
{
P256p ^= pData[i] ^ pData[i+1] ^ pData[i+2] ^ pData[i+3] ^ pData[i+4] ^ pData[i+5] ^ pData[i+6] ^ pData[i+7]
^ pData[i+8] ^ pData[i+9] ^ pData[i+10] ^ pData[i+11] ^ pData[i+12] ^ pData[i+13] ^ pData[i+14] ^ pData[i+15]
^ pData[i+16] ^ pData[i+17] ^ pData[i+18] ^ pData[i+19] ^ pData[i+20] ^ pData[i+21] ^ pData[i+22] ^ pData[i+23]
^ pData[i+24] ^ pData[i+25] ^ pData[i+26] ^ pData[i+27] ^ pData[i+28] ^ pData[i+29] ^ pData[i+30] ^ pData[i+31]
^ pData[i+64] ^ pData[i+65] ^ pData[i+66] ^ pData[i+67] ^ pData[i+68] ^ pData[i+69] ^ pData[i+70] ^ pData[i+71]
^ pData[i+72] ^ pData[i+73] ^ pData[i+74] ^ pData[i+75] ^ pData[i+76] ^ pData[i+77] ^ pData[i+78] ^ pData[i+79]
^ pData[i+80] ^ pData[i+81] ^ pData[i+82] ^ pData[i+83] ^ pData[i+84] ^ pData[i+85] ^ pData[i+86] ^ pData[i+87]
^ pData[i+88] ^ pData[i+89] ^ pData[i+90] ^ pData[i+91] ^ pData[i+92] ^ pData[i+93] ^ pData[i+94] ^ pData[i+95];
P256 ^= pData[i+32] ^ pData[i+33] ^ pData[i+34] ^ pData[i+35] ^ pData[i+36] ^ pData[i+37] ^ pData[i+38] ^ pData[i+39]
^ pData[i+40] ^ pData[i+41] ^ pData[i+42] ^ pData[i+43] ^ pData[i+44] ^ pData[i+45] ^ pData[i+46] ^ pData[i+47]
^ pData[i+48] ^ pData[i+49] ^ pData[i+50] ^ pData[i+51] ^ pData[i+52] ^ pData[i+53] ^ pData[i+54] ^ pData[i+55]
^ pData[i+56] ^ pData[i+57] ^ pData[i+58] ^ pData[i+59] ^ pData[i+60] ^ pData[i+61] ^ pData[i+62] ^ pData[i+63]
^ pData[i+96] ^ pData[i+97] ^ pData[i+98] ^ pData[i+99] ^ pData[i+100] ^ pData[i+101] ^ pData[i+102] ^ pData[i+103]
^ pData[i+104] ^ pData[i+105] ^ pData[i+106] ^ pData[i+107] ^ pData[i+108] ^ pData[i+109] ^ pData[i+110] ^ pData[i+111]
^ pData[i+112] ^ pData[i+113] ^ pData[i+114] ^ pData[i+115] ^ pData[i+116] ^ pData[i+117] ^ pData[i+118] ^ pData[i+119]
^ pData[i+120] ^ pData[i+121] ^ pData[i+122] ^ pData[i+123] ^ pData[i+124] ^ pData[i+125] ^ pData[i+126] ^ pData[i+127];
P512p ^= pData[i] ^ pData[i+1] ^ pData[i+2] ^ pData[i+3] ^ pData[i+4] ^ pData[i+5] ^ pData[i+6] ^ pData[i+7]
^ pData[i+8] ^ pData[i+9] ^ pData[i+10] ^ pData[i+11] ^ pData[i+12] ^ pData[i+13] ^ pData[i+14] ^ pData[i+15]
^ pData[i+16] ^ pData[i+17] ^ pData[i+18] ^ pData[i+19] ^ pData[i+20] ^ pData[i+21] ^ pData[i+22] ^ pData[i+23]
^ pData[i+24] ^ pData[i+25] ^ pData[i+26] ^ pData[i+27] ^ pData[i+28] ^ pData[i+29] ^ pData[i+30] ^ pData[i+31]
^ pData[i+32] ^ pData[i+33] ^ pData[i+34] ^ pData[i+35] ^ pData[i+36] ^ pData[i+37] ^ pData[i+38] ^ pData[i+39]
^ pData[i+40] ^ pData[i+41] ^ pData[i+42] ^ pData[i+43] ^ pData[i+44] ^ pData[i+45] ^ pData[i+46] ^ pData[i+47]
^ pData[i+48] ^ pData[i+49] ^ pData[i+50] ^ pData[i+51] ^ pData[i+52] ^ pData[i+53] ^ pData[i+54] ^ pData[i+55]
^ pData[i+56] ^ pData[i+57] ^ pData[i+58] ^ pData[i+59] ^ pData[i+60] ^ pData[i+61] ^ pData[i+62] ^ pData[i+63];
P512 ^= pData[i+64] ^ pData[i+65] ^ pData[i+66] ^ pData[i+67] ^ pData[i+68] ^ pData[i+69] ^ pData[i+70] ^ pData[i+71]
^ pData[i+72] ^ pData[i+73] ^ pData[i+74] ^ pData[i+75] ^ pData[i+76] ^ pData[i+77] ^ pData[i+78] ^ pData[i+79]
^ pData[i+80] ^ pData[i+81] ^ pData[i+82] ^ pData[i+83] ^ pData[i+84] ^ pData[i+85] ^ pData[i+86] ^ pData[i+87]
^ pData[i+88] ^ pData[i+89] ^ pData[i+90] ^ pData[i+91] ^ pData[i+92] ^ pData[i+93] ^ pData[i+94] ^ pData[i+95]
^ pData[i+96] ^ pData[i+97] ^ pData[i+98] ^ pData[i+99] ^ pData[i+100] ^ pData[i+101] ^ pData[i+102] ^ pData[i+103]
^ pData[i+104] ^ pData[i+105] ^ pData[i+106] ^ pData[i+107] ^ pData[i+108] ^ pData[i+109] ^ pData[i+110] ^ pData[i+111]
^ pData[i+112] ^ pData[i+113] ^ pData[i+114] ^ pData[i+115] ^ pData[i+116] ^ pData[i+117] ^ pData[i+118] ^ pData[i+119]
^ pData[i+120] ^ pData[i+121] ^ pData[i+122] ^ pData[i+123] ^ pData[i+124] ^ pData[i+125] ^ pData[i+126] ^ pData[i+127];
}
P256p = evenParity[((P256p & 0xF0) >> 4)] ^ evenParity[(P256p & 0x0F)];
P256 = evenParity[((P256 & 0xF0) >> 4)] ^ evenParity[(P256 & 0x0F)];
P512p = evenParity[((P512p & 0xF0) >> 4)] ^ evenParity[(P512p & 0x0F)];
P512 = evenParity[((P512 & 0xF0) >> 4)] ^ evenParity[(P512 & 0x0F)];
for(i=j; i<j+(DATA_BLOCK_LEN>>1); i++)
{
P1024p ^= pData[i];
P1024 ^= pData[i+128];
}
// XOR all of the data bytes (used to compute COLUMN parity terms)
dataXOR = P1024p ^ P1024;
P1024p = evenParity[((P1024p & 0xF0) >> 4)] ^ evenParity[(P1024p & 0x0F)];
P1024 = evenParity[((P1024 & 0xF0) >> 4)] ^ evenParity[(P1024 & 0x0F)];
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