/**
* pop off newest/last
* used for edifact
*/
static DmtxByte
StreamOutputChainRemoveLast(DmtxEncodeStream *stream)
{
DmtxByte value;
DmtxPassFail passFail;
if(stream->outputChainWordCount > 0)
{
value = dmtxByteListPop(stream->output, &passFail);
stream->outputChainWordCount--;
}
else
{
value = 0;
StreamMarkFatal(stream, DmtxErrorEmptyList);
}
return value;
}
/**
* remove first element from chain, shifting all following elements back by one
* used for binary length changes end condition
*/
static void
Base256OutputChainRemoveFirst(DmtxEncodeStream *stream)
{
DmtxByte value;
DmtxPassFail passFail;
int i, chainStart;
chainStart = stream->output->length - stream->outputChainWordCount;
for(i = chainStart; i < stream->output->length - 1; i++)
{
value = UnRandomize255State(stream->output->b[i+1], i+2);
stream->output->b[i] = Randomize255State(value, i + 1);
}
dmtxByteListPop(stream->output, &passFail);
if(passFail == DmtxPass)
stream->outputChainWordCount--;
else
StreamMarkFatal(stream, DmtxErrorUnknown);
}
static void
ShiftValueListBy3(DmtxByteList *list, DmtxPassFail *passFail)
{
int i;
/* Shift values */
for(i = 0; i < list->length - 3; i++)
list->b[i] = list->b[i+3];
/* Shorten list by 3 (or less) */
for(i = 0; i < 3; i++)
{
dmtxByteListPop(list, passFail);
if(*passFail == DmtxFail)
return;
if(list->length == 0)
break;
}
*passFail = DmtxPass;
}
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;
}
