crc16_kermit.h

///\file

/******************************************************************************
The MIT License(MIT)

Embedded Template Library.

Copyright(c) 2014 jwellbelove

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of this software and associated documentation files(the "Software"), to deal
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******************************************************************************/

#ifndef __etl_crc16_kermit__
#define __etl_crc16_kermit__

#include <stdint.h>

#include "static_assert.h"
#include "type_traits.h"
#include "endian.h"

///\defgroup crc16_kermit 16 bit CRC Kermit calculation
///\ingroup crc

namespace etl
{
  //***************************************************************************
  /// CRC Kermit table
  /// \ingroup crc
  //***************************************************************************
  extern const uint16_t CRC_KERMIT[];
  
  //***************************************************************************
  /// Calculates CRC-Kermit using polynomial 0x1021
  ///\tparam ENDIANNESS The endianness of the calculation for input types larger than uint8_t. Default = endian::little.
  /// \ingroup crc16_kermit
  //***************************************************************************
  template <const int ENDIANNESS = endian::little>
  class crc16_kermit
  {
  public:

    typedef uint16_t value_type;

    //*************************************************************************
    /// Default constructor.
    //*************************************************************************
    crc16_kermit()
    {
      reset();
    }

    //*************************************************************************
    /// Constructor from range.
    /// \param begin Start of the range.
    /// \param end   End of the range.
    //*************************************************************************
    template<typename TIterator>
    crc16_kermit(TIterator begin, const TIterator end)
    {
      reset();
      add(begin, end);
    }

    //*************************************************************************
    /// Resets the CRC to the initial state.
    //*************************************************************************
    void reset()
    {
      crc = 0;
    }

    //*************************************************************************
    /// \param value The value to add to the CRC.
    //*************************************************************************
    template<typename TValue>
    void add(TValue value)
    {
      STATIC_ASSERT(is_integral<TValue>::value, "Non-integral parameter");

      if (ENDIANNESS == endian::little)
      {
        for (int i = 0; i < sizeof(TValue); ++i)
        {
          add(uint8_t((value >> (i * 8)) & 0xFF));
        }
      }
      else
      {
        for (int i = sizeof(TValue) - 1; i >= 0; --i)
        {
          add(uint8_t((value >> (i * 8)) & 0xFF));
        }
      }
    }

    //*************************************************************************
    /// \param value The uint8_t to add to the CRC.
    //*************************************************************************
    void add(uint8_t value)
    {
      crc = (crc >> 8) ^ CRC_KERMIT[(crc ^ value) & 0xFF];
    }

    //*************************************************************************
    /// \param begin Start of the range.
    /// \param end   End of the range.
    //*************************************************************************
    template<typename TIterator>
    void add(TIterator begin, const TIterator end)
    {
      while (begin != end)
      {
        add(*begin);
        ++begin;
      }
    }

    //*************************************************************************
    /// Gets the CRC value.
    //*************************************************************************
    value_type value() const
    {
      return crc;
    }

    //*************************************************************************
    /// \param value The value to add to the CRC.
    //*************************************************************************
    template<typename TValue>
    crc16_kermit<ENDIANNESS>& operator +=(TValue value)
    {
      add(value);

      return *this;
    }

    //*************************************************************************
    /// Conversion operator to value_type
    //*************************************************************************
    operator value_type () const
    {
      return crc;
    }

  private:

    value_type crc;
  };
}

#endif