#include <PndHammingDecoder.h>

Public Member Functions
	PndHammingDecoder ()

virtual	~PndHammingDecoder ()

UShort_t	CheckHammingCode (ULong64_t dataword, int dataword_length)

ULong64_t	CalculateCRCTableFast (std::vector< char > p, ULong64_t len)

ULong64_t	ReflectBitsStream (ULong64_t crc, int bitnum)

std::vector< char >	ConvertData (std::vector< ULong64_t > topixFrame)

Protected Member Functions
void	GenerateCRCTable ()

Private Attributes
const UInt_t	fOrder

const ULong64_t	fPolynom

const ULong64_t	fCRCXor

const UInt_t	fRefIn

const UInt_t	fRefOut

ULong64_t	fCRCMask

ULong64_t	fCRCHighBit

ULong64_t	fCRCInit_direct

ULong64_t	fCRCTab [256]

Detailed Description

Definition at line 13 of file PndHammingDecoder.h.

Constructor & Destructor Documentation

PndHammingDecoder::PndHammingDecoder ( )

Definition at line 13 of file PndHammingDecoder.cxx.

References fCRCHighBit, fCRCMask, fOrder, and GenerateCRCTable().

                                      :
         fOrder(16), fPolynom(0x8005), fCRCXor(0x0000), fRefIn(0), fRefOut(0), fCRCInit_direct(0)
 {
         fCRCMask = ((((unsigned long)1<<(fOrder-1))-1)<<1)|1;
         fCRCHighBit = (unsigned long)1<<(fOrder-1);
 
         GenerateCRCTable();
 }

PndHammingDecoder::~PndHammingDecoder ( )

virtual

Definition at line 22 of file PndHammingDecoder.cxx.

                                       {
         // TODO Auto-generated destructor stub
 }

Member Function Documentation

ULong64_t PndHammingDecoder::CalculateCRCTableFast	(	std::vector< char >	p,
		ULong64_t	len
	)

Definition at line 75 of file PndHammingDecoder.cxx.

References fCRCInit_direct, fCRCMask, fCRCTab, fCRCXor, fOrder, fRefIn, fRefOut, and ReflectBitsStream().

Referenced by PndMvdReadInToPix4TBData::CheckDataIntegrity().

                                                                                    {
 
         // fast lookup table algorithm without augmented zero bytes, e.g. used in pkzip.
         // only usable with polynom orders of 8, 16, 24 or 32.
 
         ULong64_t crc = fCRCInit_direct;
 
         std::vector<char>::iterator it=p.begin();
 
         if (fRefIn)
           {
             crc = ReflectBitsStream(crc, fOrder);
           }
 
         if (!fRefIn)
           {
             while (len--)
                       {
                         crc = (crc << 8) ^ fCRCTab[ ((crc >> (fOrder-8)) & 0xff) ^ (*it & 0xff)];
                         it++;
                       }
           }
         else
           {
             while (len--)
               {
                 crc = (crc >> 8) ^ fCRCTab[ (crc & 0xff) ^ (*it & 0xff)];
                 it++;
               }
           }
         if (fRefOut^fRefIn)
           {
             crc = ReflectBitsStream(crc, fOrder);
           }
         crc^= fCRCXor;
         crc&= fCRCMask;
 
         return(crc);
 }

UShort_t PndHammingDecoder::CheckHammingCode	(	ULong64_t	dataword,
		int	dataword_length
	)

Definition at line 26 of file PndHammingDecoder.cxx.

References i.

Referenced by PndMvdReadInToPix4TBData::CheckDataIntegrity().

 {
         // This function expects a standard hamming encoded dataword (including hamming bits at 2^i positions) and returns the hamming bits
         // If the dataword is correct, the hamming bits are 0
         // If an error occured, the hamming bits are !=0
         // If a 1-bit error occured, the hamming bits give the possions of the wrong bit
 
         ULong64_t shift=1;
         ULong64_t hamming_code=0;
 
         if(dataword_length > 63)
         {
                 std::cout << "Error: maximum length of datastream is 63" << std::endl;
                 return 0xffff;
         }
 
         // loop over all hamming bits
         for (int i = 0; pow(2,i) < dataword_length; ++i)
         {
                 int start=pow(2,i);
                 int stepwidth=2*start;
                 int parity_bit=0;
                 for (int j = start; j < dataword_length+1; j+=stepwidth)
                 {
                         for (int k = j; k < j+stepwidth/2 && k < dataword_length+1; ++k)
                         {
                                 parity_bit ^= ((dataword & (shift <<(k-1)))>> (k-1));
                         }
                 }
                 hamming_code += (parity_bit << i);
         }
         return hamming_code;
 }

std::vector< char > PndHammingDecoder::ConvertData ( std::vector< ULong64_t > topixFrame )

Definition at line 60 of file PndHammingDecoder.cxx.

References i.

Referenced by PndMvdReadInToPix4TBData::CheckDataIntegrity().

 {
         std::vector<char> topix_data;
         for (unsigned int i = 1; i < topixFrame.size() - 1; i++) {
                 for (int j = 0; j < 8; j++) {
                         if (j == 0 or j == 1 or j == 2) {
                                 topix_data.push_back(0x00);
                         } else {
                                 topix_data.push_back((topixFrame[i] >> (7 - j) * 2 * 4) & 0xff);
                         }
                 }
         }
         return topix_data;
 }

void PndHammingDecoder::GenerateCRCTable ( )

protected

Definition at line 115 of file PndHammingDecoder.cxx.

References fCRCHighBit, fCRCMask, fCRCTab, fOrder, fPolynom, fRefIn, i, and ReflectBitsStream().

Referenced by PndHammingDecoder().

                                          {
   // make CRC lookup table used by table algorithms
         ULong64_t bit, crc;
         for (int i=0; i<256; i++) {
                 crc=(ULong64_t)i;
                 if (fRefIn)
                   {
                     crc=ReflectBitsStream(crc, 8);
                   }
                 crc<<= fOrder-8;
 
                 for (int j=0; j<8; j++)
                   {
                         bit = crc & fCRCHighBit;
                         crc<<= 1;
                         if (bit)
                           {
                             crc^= fPolynom;
                           }
                   }
                 if (fRefIn)
                   {
                     crc = ReflectBitsStream(crc, fOrder);
                   }
                 crc&= fCRCMask;
                 fCRCTab[i]= crc;
         }
 }

ULong64_t PndHammingDecoder::ReflectBitsStream	(	ULong64_t	crc,
		int	bitnum
	)

Definition at line 144 of file PndHammingDecoder.cxx.

References i.

Referenced by CalculateCRCTableFast(), and GenerateCRCTable().

                                                                         {
 
         // reflects the lower 'bitnum' bits of 'crc'
 
         ULong64_t i, j=1, crcout=0;
 
         for (i=(ULong64_t)1<<(bitnum-1); i; i>>=1)
           {
                 if (crc & i)
                   {
                     crcout|=j;
                   }
                 j<<= 1;
           }
         return (crcout);
 }