crc16_ccitt.h

///\file

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

Embedded Template Library.
https://github.com/ETLCPP/etl

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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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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******************************************************************************/

#ifndef __ETL_CRC16_CCITT__
#define __ETL_CRC16_CCITT__

#include <stdint.h>

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

#if defined(COMPILER_KEIL)
#pragma diag_suppress 1300 
#endif

///\defgroup crc16_ccitt 16 bit CRC CCITT calculation
///\ingroup crc

namespace etl
{
  //***************************************************************************
  /// CRC-CCITT table
  /// \ingroup crc16_ccitt
  //***************************************************************************
  extern const uint16_t CRC_CCITT[];

  //***************************************************************************
  /// Calculates CRC-CCITT using polynomial 0x1021
  ///\tparam ENDIANNESS The endianness of the calculation for input types larger than uint8_t. Default = endian::little.
  /// \ingroup crc16_ccitt
  //***************************************************************************
  template <const int ENDIANNESS = endian::little>
  class crc16_ccitt : public etl::ihash
  {
  public:

    typedef uint16_t value_type;
    typedef uint16_t argument_type;

    //*************************************************************************
    /// Default constructor.
    //*************************************************************************
    crc16_ccitt()
      : ihash(etl::endian(ENDIANNESS))
    {
      reset();
    }

    //*************************************************************************
    /// Constructor from range.
    /// \param begin Start of the range.
    /// \param end   End of the range.
    //*************************************************************************
    template<typename TIterator>
    crc16_ccitt(TIterator begin, const TIterator end)
      : ihash(etl::endian(ENDIANNESS))
    {
      reset();
      add(begin, end);
    }

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

    //*************************************************************************
    /// Adds a range.
    /// \param begin
    /// \param end
    //*************************************************************************
    template<typename TIterator>
    void add(TIterator begin, const TIterator end)
    {
      ihash::add(begin, end);
    }

    //*************************************************************************
    /// Adds a value.
    /// \param value The value to add to the checksum.
    //*************************************************************************
    template<typename TValue>
    void add(TValue value)
    {
      ihash::add(value);
    }

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

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

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

    //*************************************************************************
    /// Gets the generic digest value.
    //*************************************************************************
    generic_digest digest() const
    {
      return ihash::get_digest(crc);
    }

  private:

    value_type crc;
  };
}

#endif