crc.h

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// 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