ClickHouse/base/poco/Foundation/include/Poco/Checksum.h

//
// Checksum.h
//
// Library: Foundation
// Package: Core
// Module:  Checksum
//
// Definition of the Checksum class.
//
// Copyright (c) 2007, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef Foundation_Checksum_INCLUDED
#define Foundation_Checksum_INCLUDED


#include "Poco/Foundation.h"


namespace Poco
{


class Foundation_API Checksum
/// This class calculates CRC-32 or Adler-32 checksums
/// for arbitrary data.
///
/// A cyclic redundancy check (CRC) is a type of hash function, which is used to produce a
/// small, fixed-size checksum of a larger block of data, such as a packet of network
/// traffic or a computer file. CRC-32 is one of the most commonly used CRC algorithms.
///
/// Adler-32 is a checksum algorithm which was invented by Mark Adler.
/// It is almost as reliable as a 32-bit cyclic redundancy check for protecting against
/// accidental modification of data, such as distortions occurring during a transmission,
/// but is significantly faster to calculate in software.

{
public:
    enum Type
    {
        TYPE_ADLER32 = 0,
        TYPE_CRC32
    };

    Checksum();
    /// Creates a CRC-32 checksum initialized to 0.

    Checksum(Type t);
    /// Creates the Checksum, using the given type.

    ~Checksum();
    /// Destroys the Checksum.

    void update(const char * data, unsigned length);
    /// Updates the checksum with the given data.

    void update(const std::string & data);
    /// Updates the checksum with the given data.

    void update(char data);
    /// Updates the checksum with the given data.

    Poco::UInt32 checksum() const;
    /// Returns the calculated checksum.

    Type type() const;
    /// Which type of checksum are we calulcating

private:
    Type _type;
    Poco::UInt32 _value;
};


//
// inlines
//
inline void Checksum::update(const std::string & data)
{
    update(data.c_str(), static_cast<unsigned int>(data.size()));
}


inline void Checksum::update(char c)
{
    update(&c, 1);
}


inline Poco::UInt32 Checksum::checksum() const
{
    return _value;
}


inline Checksum::Type Checksum::type() const
{
    return _type;
}


} // namespace Poco


#endif // Foundation_Checksum_INCLUDED