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#include "lib9.h"
#include "logfs.h"
#include "nandfs.h"
#include "local.h"
static int
hammingdistance(uchar a, uchar b)
{
uchar c;
int i, k;
if (a == b)
return 0;
c = a ^ b;
for (i = 0x80, k = 0; i; i >>= 1)
if (c & i)
k++;
return k;
}
static int
allones(uchar *data, int len)
{
while (len-- > 0)
if (*data++ != 0xff)
return 0;
return 1;
}
LogfsLowLevelReadResult
_nandfscorrectauxiliary(NandfsAuxiliary *hdr)
{
/*
* correct single bit errors, detect more than 1, in
* tag, signature
* TODO: add nerase and path protection
*/
LogfsLowLevelReadResult e;
int x;
int min, minx;
e = LogfsLowLevelReadResultOk;
min = 8;
minx = 0;
for (x = 0; x < _nandfsvalidtagscount; x++) {
int d = hammingdistance(hdr->tag, _nandfsvalidtags[x]);
if (d < min) {
min = d;
minx = x;
if (d == 0)
break;
}
}
if (min == 1) {
hdr->tag = _nandfsvalidtags[minx];
e = LogfsLowLevelReadResultSoftError;
}
else if (min > 1)
e = LogfsLowLevelReadResultHardError;
else {
if (hdr->tag != LogfsTnone) {
ulong tmp = getbig4(hdr->parth);
if (tmp != 0xfffffffff && _nandfshamming31_26correct(&tmp)) {
putbig4(hdr->parth, tmp);
if (e != LogfsLowLevelReadResultOk)
e = LogfsLowLevelReadResultSoftError;
}
tmp = (getbig2(hdr->nerasemagicmsw) << 16) | getbig2(hdr->nerasemagiclsw);
if (tmp != 0xffffffff && _nandfshamming31_26correct(&tmp)) {
putbig2(hdr->nerasemagicmsw, tmp >> 16);
putbig2(hdr->nerasemagiclsw, tmp);
if (e != LogfsLowLevelReadResultOk)
e = LogfsLowLevelReadResultSoftError;
}
}
else if (allones((uchar *)hdr, sizeof(*hdr)))
e = LogfsLowLevelReadResultAllOnes;
}
return e;
}
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