bitdecoder.h

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/*
 * atMETEO - An ATmega based weather station
 * Copyright (C) 2014-2015 Christian Fetzer
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#pragma once

#include <limits.h>  // AVR toolchain doesn't offer climits header

#include "utils.h"

namespace Sensors
{

enum class BitDecoderStatus : uint8_t {
    Complete = 0,

    Incomplete,

    ParityError
};

template <typename T>
struct MsbBitNumbering
{
    static void bitWrite(T &data, uint8_t bit, bool value)
    {
        Sensors::bitWrite(data, sizeof(T) * CHAR_BIT - 1 - bit, value);
    }
};

template <typename T>
struct LsbBitNumbering
{
    static void bitWrite(T &data, uint8_t bit, bool value)
    {
        Sensors::bitWrite(data, bit, value);
    }
};

template <typename T>
struct NoParity
{
};

template <typename T>
struct EvenParity
{
    static bool parityCheck(T data, bool parity)
    {
        return Sensors::parity(data) == parity;
    }
};
template <typename T>
struct OddParity
{
    static bool parityCheck(T data, bool parity)
    {
        return Sensors::parity(data) != parity;
    }
};

template <typename T, typename BitDecoder>
class BitDecoderBase
{
public:
    BitDecoderStatus addBit(bool value)
    {
        if (static_cast<BitDecoder *>(this)->isComplete())
            reset();

        return static_cast<BitDecoder *>(this)->internalAddBit(value);
    }

    T getData() const
    {
        return m_data;
    }

    void reset()
    {
        m_bitLength = 0;
        m_data = 0;
    }

protected:
    BitDecoderBase()
    {
        reset();
    }

    T m_data;
    uint8_t m_bitLength;
};

template <typename T,
          template <typename> class TParity,
          template <typename> class TBitNumbering>
class BitDecoder
        : public BitDecoderBase<T, BitDecoder<T, TParity, TBitNumbering>>
{
    friend class BitDecoderBase<T, BitDecoder<T, TParity, TBitNumbering>>;

    BitDecoderStatus internalAddBit(bool value)
    {
        // Data bit
        if (this->m_bitLength < sizeof(T) * CHAR_BIT) {
            TBitNumbering<T>::bitWrite(this->m_data, this->m_bitLength, value);
        }

        // Parity bit
        else {
            if (!TParity<T>::parityCheck(this->m_data, value)) {
                return BitDecoderStatus::ParityError;
            }
        }

        ++this->m_bitLength;
        return isComplete() ? BitDecoderStatus::Complete :
                              BitDecoderStatus::Incomplete;
    }

    bool isComplete()
    {
        return this->m_bitLength == sizeof(T) * CHAR_BIT + 1;
    }
};

template <typename T,
          template <typename> class TBitNumbering>
class BitDecoder<T, NoParity, TBitNumbering>
        : public BitDecoderBase<T, BitDecoder<T, NoParity, TBitNumbering>>
{
    friend class BitDecoderBase<T, BitDecoder<T, NoParity, TBitNumbering>>;

private:
    BitDecoderStatus internalAddBit(bool value)
    {
        TBitNumbering<T>::bitWrite(this->m_data, this->m_bitLength++, value);
        return isComplete() ? BitDecoderStatus::Complete :
                              BitDecoderStatus::Incomplete;
    }

    bool isComplete()
    {
        return this->m_bitLength == sizeof(T) * CHAR_BIT;
    }
};

template <template <typename> class TParity,
          template <typename> class TBitNumbering>
using ByteDecoder = BitDecoder<uint8_t, TParity, TBitNumbering>;
  // \addtogroup libsensors_decoder

}  // namespace Sensors