// crc.h - originally written and placed in the public domain by Wei Dai

/// \file crc.h

/// \brief Classes for CRC-32 and CRC-32C checksum algorithm

#ifndef CRYPTOPP_CRC32_H

#define CRYPTOPP_CRC32_H

#include "cryptlib.h"

NAMESPACE_BEGIN(CryptoPP)

const word32 CRC32_NEGL = 0xffffffffL;

#if (CRYPTOPP_LITTLE_ENDIAN)

#define CRC32_INDEX(c) (c & 0xff)

#define CRC32_SHIFTED(c) (c >> 8)

#else

#define CRC32_INDEX(c) (c >> 24)

#define CRC32_SHIFTED(c) (c << 8)

#endif

/// \brief CRC-32 Checksum Calculation

/// \details Uses CRC polynomial 0xEDB88320

class CRC32 : public HashTransformation

{

public:

  CRYPTOPP_CONSTANT(DIGESTSIZE = 4);

  CRC32();

  void Update(const byte *input, size_t length);

  void TruncatedFinal(byte *hash, size_t size);

  unsigned int DigestSize() const {return DIGESTSIZE;}

  CRYPTOPP_STATIC_CONSTEXPR const char* StaticAlgorithmName() {return "CRC32";}

  std::string AlgorithmName() const {return StaticAlgorithmName();}

  /// \brief Updates a CRC with additional input

  /// \param b the additional input as a byte

  void UpdateByte(byte b) {m_crc = m_tab[CRC32_INDEX(m_crc) ^ b] ^ CRC32_SHIFTED(m_crc);}

  /// \brief Retrieves the i-th byte of the CRC

  /// \param i the additional input as a byte

  /// \return the byte at the i-th position

  byte GetCrcByte(size_t i) const {return reinterpret_cast<const byte *>(&m_crc)[i];}

  std::string AlgorithmProvider() const;

protected:

  void Reset() {m_crc = CRC32_NEGL;}

private:

  static const word32 m_tab[256];

  word32 m_crc;

};

/// \brief CRC-32C Checksum Calculation

/// \details Uses CRC polynomial 0x82F63B78

/// \since Crypto++ 5.6.4

class CRC32C : public HashTransformation

{

public:

  CRYPTOPP_CONSTANT(DIGESTSIZE = 4);

  CRC32C();

  void Update(const byte *input, size_t length);

  void TruncatedFinal(byte *hash, size_t size);

  unsigned int DigestSize() const {return DIGESTSIZE;}

  CRYPTOPP_STATIC_CONSTEXPR const char* StaticAlgorithmName() {return "CRC32C";}

  std::string AlgorithmName() const {return StaticAlgorithmName();}

  /// \brief Updates a CRC with additional input

  /// \param b the additional input as a byte

  void UpdateByte(byte b) {m_crc = m_tab[CRC32_INDEX(m_crc) ^ b] ^ CRC32_SHIFTED(m_crc);}

  /// \brief Retrieves the i-th byte of the CRC

  /// \param i the additional input as a byte

  /// \return the byte at the i-th position

  byte GetCrcByte(size_t i) const {return reinterpret_cast<const byte *>(&m_crc)[i];}

  std::string AlgorithmProvider() const;

protected:

  void Reset() {m_crc = CRC32_NEGL;}

private:

  static const word32 m_tab[256];

  word32 m_crc;

};

NAMESPACE_END

#endif