GenericCrc Class Reference

#include <GenericCrc.h>

Collaboration diagram for GenericCrc:

Public Member Functions
	GenericCrc ()
	Provides a library of known CRC(like) algorithms.
	~GenericCrc ()
uint32_t	crc9fibre (const std::vector< uint32_t > &inwords, size_t num_bits) const
	Functions calculating CRC over input data.
uint32_t	crc20rod (const std::vector< uint32_t > &inwords, size_t num_bits) const

Detailed Description

Definition at line 9 of file GenericCrc.h.

Constructor & Destructor Documentation

GenericCrc()

GenericCrc::GenericCrc ( )

inline

Provides a library of known CRC(like) algorithms.

GenericCrc is a stateless class which just provides a collection of CRC-like functions for various stages of data processing

Definition at line 20 of file GenericCrc.h.

{}

~GenericCrc()

GenericCrc::~GenericCrc ( )

inline

Definition at line 21 of file GenericCrc.h.

{}

Member Function Documentation

crc20rod()

uint32_t GenericCrc::crc20rod	(	const std::vector< uint32_t > &	inwords,
		size_t	num_bits ) const

Definition at line 33 of file GenericCrc.cxx.

{
  int order = 20;
  uint32_t val  = 0xfffff;
  //<<uint32_t poly = 0x18349f;   // Old, wrong, polynomial used until December 2021
  uint32_t poly = 0x18359f;
  size_t num_words = inwords.size();
  if ( (num_bits+31)/32 > num_words )
  {
    std::cout << "ERROR: not enough words (" << num_words << ") for " << num_bits << "-bit CRC calculation." << std::endl;
    return 0;
  }
  for ( int i = 0 ; i < order ; ++i )
  {
    int flip = val&1;
    val >>= 1;
    if ( flip )
      val ^= (poly>>1);
  }
  for ( size_t i = 0 ; i < num_bits ; ++i )
  {
    val <<= 1;
    val |= (inwords[i/32]>>(31-i%32))&1;
    if ((val>>order)&1)
      val ^= poly;
  }
  for ( int i = 0 ; i < order ; ++i )
  {
    val <<= 1;
    if ((val>>order)&1)
      val ^= poly;
  }
  return val;
}

crc9fibre()

uint32_t GenericCrc::crc9fibre	(	const std::vector< uint32_t > &	inwords,
		size_t	num_bits ) const

Functions calculating CRC over input data.

CRC9 with polynomial 1011111011 over num_bits bits

Uses a more succinct CRC calculation and flexible in terms of digits, checked versus old code but only supports bit reversal = true

Definition at line 5 of file GenericCrc.cxx.

{
 
    size_t num_words = inwords.size();
    if ( (num_bits+31)/32 > num_words )
    {
      std::cout << "ERROR: not enough words (" << num_words << ") for " << num_bits << "-bit CRC calculation." << std::endl;
      return 0;
    }
    uint32_t val = 0x1ff;
    for ( size_t i = 0 ; i < num_bits ; ++i )
    {
      if ( (inwords.at(i/32)>>(i%32)) & 1 )
        val ^= 1;
      if ( val&1 )
        val ^= 0x37d;     // 1101111101 = polynomial reversed
      val >>= 1;
    }
    return val;
} 

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The documentation for this class was generated from the following files:

• GenericCrc.h
• GenericCrc.cxx