DmtxBoolean
RsFindErrorLocations(DmtxByteList *loc, const DmtxByteList *elp)
{
int i, j;
int lambda = elp->length - 1;
DmtxPassFail passFail;
DmtxByte q, regStorage[MAX_ERROR_WORD_COUNT];
DmtxByteList reg = dmtxByteListBuild(regStorage, sizeof(regStorage));
dmtxByteListCopy(®, elp, &passFail); CHKPASS;
dmtxByteListInit(loc, 0, 0, &passFail); CHKPASS;
for(i = 1; i <= NN; i++)
{
for(q = 1, j = 1; j <= lambda; j++)
{
reg.b[j] = GfMultAntilog(reg.b[j], j);
q = GfAdd(q, reg.b[j]);
}
if(q == 0)
{
dmtxByteListPush(loc, NN - i, &passFail); CHKPASS;
}
}
return (loc->length == lambda) ? DmtxTrue : DmtxFalse;
}
DmtxPassFail
RsRepairErrors(DmtxByteList *rec, const DmtxByteList *loc, const DmtxByteList *elp, const DmtxByteList *syn)
{
int i, j, q;
int lambda = elp->length - 1;
DmtxPassFail passFail;
DmtxByte zVal, root, err;
DmtxByte zStorage[MAX_ERROR_WORD_COUNT+1];
DmtxByteList z = dmtxByteListBuild(zStorage, sizeof(zStorage));
/* Form polynomial z(x) */
dmtxByteListPush(&z, 1, &passFail); CHKPASS;
for(i = 1; i <= lambda; i++)
{
for(zVal = GfAdd(syn->b[i], elp->b[i]), j = 1; j < i; j++)
zVal= GfAdd(zVal, GfMult(elp->b[i-j], syn->b[j]));
dmtxByteListPush(&z, zVal, &passFail); CHKPASS;
}
for(i = 0; i < lambda; i++)
{
/* Calculate numerator of error term */
root = NN - loc->b[i];
for(err = 1, j = 1; j <= lambda; j++)
err = GfAdd(err, GfMultAntilog(z.b[j], j * root));
if(err == 0)
continue;
/* Calculate denominator of error term */
for(q = 0, j = 0; j < lambda; j++)
{
if(j != i)
q += log301[1 ^ antilog301[(loc->b[j] + root) % NN]];
}
q %= NN;
err = GfMultAntilog(err, NN - q);
rec->b[loc->b[i]] = GfAdd(rec->b[loc->b[i]], err);
}
return DmtxPass;
}
/**
* push on newest/last append
* used for encoding each output cw
*/
static void
StreamOutputChainAppend(DmtxEncodeStream *stream, DmtxByte value)
{
DmtxPassFail passFail;
dmtxByteListPush(stream->output, value, &passFail);
if(passFail == DmtxPass)
stream->outputChainWordCount++;
else
StreamMarkFatal(stream, DmtxErrorOutOfBounds);
}
/**
* insert element at beginning of chain, shifting all following elements forward by one
* used for binary length changes
*/
static void
Base256OutputChainInsertFirst(DmtxEncodeStream *stream)
{
DmtxByte value;
DmtxPassFail passFail;
int i, chainStart;
chainStart = stream->output->length - stream->outputChainWordCount;
dmtxByteListPush(stream->output, 0, &passFail);
if(passFail == DmtxPass)
{
for(i = stream->output->length - 1; i > chainStart; i--)
{
value = UnRandomize255State(stream->output->b[i-1], i);
stream->output->b[i] = Randomize255State(value, i + 1);
}
stream->outputChainWordCount++;
}
else
{
StreamMarkFatal(stream, DmtxErrorUnknown);
}
}
DmtxBoolean
RsFindErrorLocatorPoly(DmtxByteList *elpOut, const DmtxByteList *syn, int errorWordCount, int maxCorrectable)
{
int i, iNext, j;
int m, mCmp, lambda;
DmtxByte disTmp, disStorage[MAX_ERROR_WORD_COUNT+1];
DmtxByte elpStorage[MAX_ERROR_WORD_COUNT+2][MAX_ERROR_WORD_COUNT];
DmtxByteList dis, elp[MAX_ERROR_WORD_COUNT+2];
DmtxPassFail passFail;
dis = dmtxByteListBuild(disStorage, sizeof(disStorage));
dmtxByteListInit(&dis, 0, 0, &passFail); CHKPASS;
for(i = 0; i < MAX_ERROR_WORD_COUNT + 2; i++)
{
elp[i] = dmtxByteListBuild(elpStorage[i], sizeof(elpStorage[i]));
dmtxByteListInit(&elp[i], 0, 0, &passFail); CHKPASS;
}
/* iNext = 0 */
dmtxByteListPush(&elp[0], 1, &passFail); CHKPASS;
dmtxByteListPush(&dis, 1, &passFail); CHKPASS;
/* iNext = 1 */
dmtxByteListPush(&elp[1], 1, &passFail); CHKPASS;
dmtxByteListPush(&dis, syn->b[1], &passFail); CHKPASS;
for(iNext = 2, i = 1; /* explicit break */; i = iNext++)
{
if(dis.b[i] == 0)
{
/* Simple case: Copy directly from previous iteration */
dmtxByteListCopy(&elp[iNext], &elp[i], &passFail); CHKPASS;
}
else
{
/* Find earlier iteration (m) that provides maximal (m - lambda) */
for(m = 0, mCmp = 1; mCmp < i; mCmp++)
if(dis.b[mCmp] != 0 && (mCmp - elp[mCmp].length) >= (m - elp[m].length))
m = mCmp;
/* Calculate error location polynomial elp[i] (set 1st term) */
for(lambda = elp[m].length - 1, j = 0; j <= lambda; j++)
elp[iNext].b[j+i-m] = antilog301[(NN - log301[dis.b[m]] +
log301[dis.b[i]] + log301[elp[m].b[j]]) % NN];
/* Calculate error location polynomial elp[i] (add 2nd term) */
for(lambda = elp[i].length - 1, j = 0; j <= lambda; j++)
elp[iNext].b[j] = GfAdd(elp[iNext].b[j], elp[i].b[j]);
elp[iNext].length = max(elp[i].length, elp[m].length + i - m);
}
lambda = elp[iNext].length - 1;
if(i == errorWordCount || i >= lambda + maxCorrectable)
break;
/* Calculate discrepancy dis.b[i] */
for(disTmp = syn->b[iNext], j = 1; j <= lambda; j++)
disTmp = GfAdd(disTmp, GfMult(syn->b[iNext-j], elp[iNext].b[j]));
assert(dis.length == iNext);
dmtxByteListPush(&dis, disTmp, &passFail); CHKPASS;
}
dmtxByteListCopy(elpOut, &elp[iNext], &passFail); CHKPASS;
return (lambda <= maxCorrectable) ? DmtxTrue : DmtxFalse;
}
DmtxPassFail
RsDecode(unsigned char *code, int sizeIdx, int fix)
{
int i;
int blockStride, blockIdx;
int blockDataWords, blockErrorWords, blockTotalWords, blockMaxCorrectable;
int symbolDataWords, symbolErrorWords, symbolTotalWords;
DmtxBoolean error, repairable;
DmtxPassFail passFail;
unsigned char *word;
DmtxByte elpStorage[MAX_ERROR_WORD_COUNT];
DmtxByte synStorage[MAX_ERROR_WORD_COUNT+1];
DmtxByte recStorage[NN];
DmtxByte locStorage[NN];
DmtxByteList elp = dmtxByteListBuild(elpStorage, sizeof(elpStorage));
DmtxByteList syn = dmtxByteListBuild(synStorage, sizeof(synStorage));
DmtxByteList rec = dmtxByteListBuild(recStorage, sizeof(recStorage));
DmtxByteList loc = dmtxByteListBuild(locStorage, sizeof(locStorage));
blockStride = dmtxGetSymbolAttribute(DmtxSymAttribInterleavedBlocks, sizeIdx);
blockErrorWords = dmtxGetSymbolAttribute(DmtxSymAttribBlockErrorWords, sizeIdx);
blockMaxCorrectable = dmtxGetSymbolAttribute(DmtxSymAttribBlockMaxCorrectable, sizeIdx);
symbolDataWords = dmtxGetSymbolAttribute(DmtxSymAttribSymbolDataWords, sizeIdx);
symbolErrorWords = dmtxGetSymbolAttribute(DmtxSymAttribSymbolErrorWords, sizeIdx);
symbolTotalWords = symbolDataWords + symbolErrorWords;
/* For each interleaved block */
for(blockIdx = 0; blockIdx < blockStride; blockIdx++)
{
/* Data word count depends on blockIdx due to special case at 144x144 */
blockDataWords = dmtxGetBlockDataSize(sizeIdx, blockIdx);
blockTotalWords = blockErrorWords + blockDataWords;
/* Populate received list (rec) with data and error codewords */
dmtxByteListInit(&rec, 0, 0, &passFail); CHKPASS;
/* Start with final error word and work backward */
word = code + symbolTotalWords + blockIdx - blockStride;
for(i = 0; i < blockErrorWords; i++)
{
dmtxByteListPush(&rec, *word, &passFail); CHKPASS;
word -= blockStride;
}
/* Start with final data word and work backward */
word = code + blockIdx + (blockStride * (blockDataWords - 1));
for(i = 0; i < blockDataWords; i++)
{
dmtxByteListPush(&rec, *word, &passFail); CHKPASS;
word -= blockStride;
}
/* Compute syndromes (syn) */
error = RsComputeSyndromes(&syn, &rec, blockErrorWords);
/* Error(s) detected: Attempt repair */
if(error)
{
/* Find error locator polynomial (elp) */
repairable = RsFindErrorLocatorPoly(&elp, &syn, blockErrorWords, blockMaxCorrectable);
if(!repairable)
return DmtxFail;
/* Find error positions (loc) */
repairable = RsFindErrorLocations(&loc, &elp);
if(!repairable)
return DmtxFail;
/* Find error values and repair */
RsRepairErrors(&rec, &loc, &elp, &syn);
}
/*
* Overwrite output with correct/corrected values
*/
/* Start with first data word and work forward */
word = code + blockIdx;
for(i = 0; i < blockDataWords; i++)
{
*word = dmtxByteListPop(&rec, &passFail); CHKPASS;
word += blockStride;
}
/* Start with first error word and work forward */
word = code + symbolDataWords + blockIdx;
for(i = 0; i < blockErrorWords; i++)
{
*word = dmtxByteListPop(&rec, &passFail); CHKPASS;
word += blockStride;
}
}
return DmtxPass;
}
static void
PushCTXValues(DmtxByteList *valueList, DmtxByte inputValue, int targetScheme,
DmtxPassFail *passFail)
{
assert(valueList->length <= 2);
/* Handle extended ASCII with Upper Shift character */
if(inputValue > 127)
{
if(targetScheme == DmtxSchemeX12)
{
*passFail = DmtxFail;
return;
}
else
{
dmtxByteListPush(valueList, DmtxValueCTXShift2, passFail); RETURN_IF_FAIL;
dmtxByteListPush(valueList, 30, passFail); RETURN_IF_FAIL;
inputValue -= 128;
}
}
/* Handle all other characters according to encodation scheme */
if(targetScheme == DmtxSchemeX12)
{
if(inputValue == 13)
{
dmtxByteListPush(valueList, 0, passFail); RETURN_IF_FAIL;
}
else if(inputValue == 42)
{
dmtxByteListPush(valueList, 1, passFail); RETURN_IF_FAIL;
}
else if(inputValue == 62)
{
dmtxByteListPush(valueList, 2, passFail); RETURN_IF_FAIL;
}
else if(inputValue == 32)
{
dmtxByteListPush(valueList, 3, passFail); RETURN_IF_FAIL;
}
else if(inputValue >= 48 && inputValue <= 57)
{
dmtxByteListPush(valueList, inputValue - 44, passFail); RETURN_IF_FAIL;
}
else if(inputValue >= 65 && inputValue <= 90)
{
dmtxByteListPush(valueList, inputValue - 51, passFail); RETURN_IF_FAIL;
}
else
{
*passFail = DmtxFail;
return;
}
}
else
{
/* targetScheme is C40 or Text */
if(inputValue <= 31)
{
dmtxByteListPush(valueList, DmtxValueCTXShift1, passFail); RETURN_IF_FAIL;
dmtxByteListPush(valueList, inputValue, passFail); RETURN_IF_FAIL;
}
else if(inputValue == 32)
{
dmtxByteListPush(valueList, 3, passFail); RETURN_IF_FAIL;
}
else if(inputValue <= 47)
{
dmtxByteListPush(valueList, DmtxValueCTXShift2, passFail); RETURN_IF_FAIL;
dmtxByteListPush(valueList, inputValue - 33, passFail); RETURN_IF_FAIL;
}
else if(inputValue <= 57)
{
dmtxByteListPush(valueList, inputValue - 44, passFail); RETURN_IF_FAIL;
}
else if(inputValue <= 64)
{
dmtxByteListPush(valueList, DmtxValueCTXShift2, passFail); RETURN_IF_FAIL;
dmtxByteListPush(valueList, inputValue - 43, passFail); RETURN_IF_FAIL;
}
else if(inputValue <= 90 && targetScheme == DmtxSchemeC40)
{
dmtxByteListPush(valueList, inputValue - 51, passFail); RETURN_IF_FAIL;
}
else if(inputValue <= 90 && targetScheme == DmtxSchemeText)
{
dmtxByteListPush(valueList, DmtxValueCTXShift3, passFail); RETURN_IF_FAIL;
dmtxByteListPush(valueList, inputValue - 64, passFail); RETURN_IF_FAIL;
}
else if(inputValue <= 95)
{
dmtxByteListPush(valueList, DmtxValueCTXShift2, passFail); RETURN_IF_FAIL;
dmtxByteListPush(valueList, inputValue - 69, passFail); RETURN_IF_FAIL;
}
else if(inputValue == 96 && targetScheme == DmtxSchemeText)
{
dmtxByteListPush(valueList, DmtxValueCTXShift3, passFail); RETURN_IF_FAIL;
dmtxByteListPush(valueList, 0, passFail); RETURN_IF_FAIL;
}
else if(inputValue <= 122 && targetScheme == DmtxSchemeText)
{
dmtxByteListPush(valueList, inputValue - 83, passFail); RETURN_IF_FAIL;
}
else if(inputValue <= 127)
{
dmtxByteListPush(valueList, DmtxValueCTXShift3, passFail); RETURN_IF_FAIL;
dmtxByteListPush(valueList, inputValue - 96, passFail); RETURN_IF_FAIL;
}
else
{
*passFail = DmtxFail;
return;
}
}
*passFail = DmtxPass;
}
/**
* The remaining values can exist in 3 possible cases:
*
* a) 1 C40/Text/X12 remaining == 1 data
* b) 2 C40/Text/X12 remaining == 1 shift + 1 data
* c) 2 C40/Text/X12 remaining == 1 data + 1 data
*
* To distinguish between cases (b) and (c), encode the final input value to
* C40/Text/X12 in a temporary location and check the resulting length. If
* it expands to multiple values it represents (b); otherwise it is (c). This
* accounts for both shift and upper shift conditions.
*
* Note that in cases (a) and (c) the final C40/Text/X12 value encoded in the
* previous chunk may have been a shift value, but this will be ignored by
* the decoder due to the implicit shift to ASCII. <-- what if symbol is much
* larger though?
*
* Term Value Symbol Codeword
* Cond Count Remain Sequence
* ---- ------- ------ ------------------------
* (b) C40 2 2 C40+C40+0
* (d) ASCII 1 1 ASCII (implicit unlatch)
* (c) ASCII 1 2 UNLATCH ASCII
* - - UNLATCH (finish ASCII)
*/
static void
CompletePartialC40Text(DmtxEncodeStream *stream, DmtxByteList *valueList, int sizeIdxRequest)
{
int i;
int sizeIdx1, sizeIdx2;
int symbolRemaining1, symbolRemaining2;
DmtxPassFail passFail;
DmtxByte inputValue;
DmtxByte outputTmpStorage[4];
DmtxByteList outputTmp = dmtxByteListBuild(outputTmpStorage, sizeof(outputTmpStorage));
if(stream->currentScheme != DmtxSchemeC40 && stream->currentScheme != DmtxSchemeText)
{
StreamMarkFatal(stream, DmtxErrorUnexpectedScheme);
return;
}
/* Should have exactly one or two input values left */
assert(valueList->length == 1 || valueList->length == 2);
sizeIdx1 = FindSymbolSize(stream->output->length + 1, sizeIdxRequest);
sizeIdx2 = FindSymbolSize(stream->output->length + 2, sizeIdxRequest);
symbolRemaining1 = GetRemainingSymbolCapacity(stream->output->length, sizeIdx1);
symbolRemaining2 = GetRemainingSymbolCapacity(stream->output->length, sizeIdx2);
if(valueList->length == 2 && symbolRemaining2 == 2)
{
/* End of symbol condition (b) -- Use Shift1 to pad final list value */
dmtxByteListPush(valueList, DmtxValueCTXShift1, &passFail); CHKPASS;
AppendValuesCTX(stream, valueList); CHKERR;
StreamMarkComplete(stream, sizeIdx2);
}
else
{
/*
* Rollback progress of previously consumed input value(s) since ASCII
* encoder will be used to finish the symbol. 2 rollbacks are needed if
* valueList holds 2 data words (i.e., not shifts or upper shifts).
*/
StreamInputAdvancePrev(stream); CHKERR;
inputValue = StreamInputPeekNext(stream); CHKERR;
/* Test-encode most recently consumed input value to C40/Text/X12 */
PushCTXValues(&outputTmp, inputValue, stream->currentScheme, &passFail);
if(valueList->length == 2 && outputTmp.length == 1)
StreamInputAdvancePrev(stream); CHKERR;
/* Re-use outputTmp to hold ASCII representation of 1-2 input values */
/* XXX Refactor how the DmtxByteList is passed back here */
outputTmp = EncodeTmpRemainingInAscii(stream, outputTmpStorage,
sizeof(outputTmpStorage), &passFail);
if(passFail == DmtxFail)
{
StreamMarkFatal(stream, DmtxErrorUnknown);
return;
}
if(outputTmp.length == 1 && symbolRemaining1 == 1)
{
/* End of symbol condition (d) */
EncodeChangeScheme(stream, DmtxSchemeAscii, DmtxUnlatchImplicit); CHKERR;
AppendValueAscii(stream, outputTmp.b[0]); CHKERR;
/* Register progress since encoding happened outside normal path */
stream->inputNext = stream->input->length;
StreamMarkComplete(stream, sizeIdx1);
}
else
{
/* Finish in ASCII (c) */
EncodeChangeScheme(stream, DmtxSchemeAscii, DmtxUnlatchExplicit); CHKERR;
for(i = 0; i < outputTmp.length; i++)
AppendValueAscii(stream, outputTmp.b[i]); CHKERR;
sizeIdx1 = FindSymbolSize(stream->output->length, sizeIdxRequest);
PadRemainingInAscii(stream, sizeIdx1);
/* Register progress since encoding happened outside normal path */
stream->inputNext = stream->input->length;
StreamMarkComplete(stream, sizeIdx1);
}
}
}
