etl/checksum.h

///\file

/******************************************************************************
The MIT License(MIT)
Embedded Template Library.
https://github.com/ETLCPP/etl
http://www.etlcpp.com
Copyright(c) 2014 jwellbelove
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files(the "Software"), to deal
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
******************************************************************************/

#ifndef __ETL_CHECKSUM__
#define __ETL_CHECKSUM__

#include <stdint.h>

#include "static_assert.h"
#include "type_traits.h"
#include "binary.h"

///\defgroup checksum Checksum calculation
///\ingroup maths

namespace etl
{
  //***************************************************************************
  /// Standard addition checksum policy.
  //***************************************************************************
  template <typename T>
  struct checksum_policy_sum
  {
    inline T initial() const
    {
      return 0;
    }

    inline T add(T sum, uint8_t value) const
    {
      return sum + value;
    }

    inline T final(T sum) const
    {
      return sum;
    }
  };

  //***************************************************************************
  /// BSD checksum policy.
  //***************************************************************************
  template <typename T>
  struct checksum_policy_bsd
  {
    inline T initial() const
    {
      return 0;
    }

    inline T add(T sum, uint8_t value) const
    {
      return etl::rotate_right(sum) + value;
    }

    inline T final(T sum) const
    {
      return sum;
    }
  };

  //***************************************************************************
  /// Standard XOR checksum policy.
  //***************************************************************************
  template <typename T>
  struct checksum_policy_xor
  {
    inline T initial() const
    {
      return 0;
    }

    inline T add(T sum, uint8_t value) const
    {
      return sum ^ value;
    }

    inline T final(T sum) const
    {
      return sum;
    }
  };

  //***************************************************************************
  /// Calculates a checksum according to the specified policy.
  ///\tparam TSum      The type used for the sum.
  ///\tparam TPolicy   The type used to enact the policy. Default = checksum_policy_sum
  ///\ingroup checksum
  //***************************************************************************
  template <typename TSum, typename TPolicy = checksum_policy_sum<TSum> >
  class checksum
  {
  public:

    STATIC_ASSERT(etl::is_unsigned<TSum>::value, "Signed TSum template parameter not supported");

    typedef TSum    value_type;
    typedef TPolicy policy_type;

    //*************************************************************************
    /// Default constructor.
    //*************************************************************************
    checksum()
    {
      reset();
    }

    //*************************************************************************
    /// Constructor from range.
    /// \param begin Start of the range.
    /// \param end   End of the range.
    //*************************************************************************
    template<typename TIterator>
    checksum(TIterator begin, const TIterator end)
    {
      STATIC_ASSERT(sizeof(typename std::iterator_traits<TIterator>::value_type) == 1, "Type not supported");

      reset();
      add(begin, end);
    }

    //*************************************************************************
    /// Resets the CRC to the initial state.
    //*************************************************************************
    void reset()
    {
      sum = policy.initial();
    }

    //*************************************************************************
    /// Adds a range.
    /// \param begin
    /// \param end
    //*************************************************************************
    template<typename TIterator>
    void add(TIterator begin, const TIterator end)
    {
      STATIC_ASSERT(sizeof(typename std::iterator_traits<TIterator>::value_type) == 1, "Type not supported");

      while (begin != end)
      {
        sum = policy.add(sum, *begin++);
      }
    }

    //*************************************************************************
    /// \param value The uint8_t to add to the checksum.
    //*************************************************************************
    void add(uint8_t value)
    {
      sum = policy.add(sum, value);
    }

    //*************************************************************************
    /// Gets the checksum value.
    //*************************************************************************
    value_type value() const
    {
      return policy.final(sum);
    }

    //*************************************************************************
    /// Conversion operator to value_type.
    //*************************************************************************
    operator value_type () const
    {
      return policy.final(sum);
    }

  private:

    value_type  sum;
    policy_type policy;
  };

  //*************************************************************************
  /// BSD Checksum.
  //*************************************************************************
  template <typename T>
  class bsd_checksum : public etl::checksum<T, etl::checksum_policy_bsd<T> >
  {
  public:

    //*************************************************************************
    /// Default constructor.
    //*************************************************************************
    bsd_checksum()
    {
      reset();
    }

    //*************************************************************************
    /// Constructor from range.
    /// \param begin Start of the range.
    /// \param end   End of the range.
    //*************************************************************************
    template<typename TIterator>
    bsd_checksum(TIterator begin, const TIterator end)
    {
      STATIC_ASSERT(sizeof(typename std::iterator_traits<TIterator>::value_type) == 1, "Type not supported");

      reset();
      add(begin, end);
    }
  };

  //*************************************************************************
  /// XOR Checksum.
  //*************************************************************************
  template <typename T>
  class xor_checksum : public etl::checksum<T, etl::checksum_policy_xor<T> >
  {
  public:

    //*************************************************************************
    /// Default constructor.
    //*************************************************************************
    xor_checksum()
    {
      reset();
    }

    //*************************************************************************
    /// Constructor from range.
    /// \param begin Start of the range.
    /// \param end   End of the range.
    //*************************************************************************
    template<typename TIterator>
    xor_checksum(TIterator begin, const TIterator end)
    {
      STATIC_ASSERT(sizeof(typename std::iterator_traits<TIterator>::value_type) == 1, "Type not supported");

      reset();
      add(begin, end);
    }
  };

}

#endif