bit_stream.hpp

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/*
 * Copyright (C) 2014 Pavel Kirienko <pavel.kirienko@gmail.com>
 */

#ifndef UAVCAN_MARSHAL_BIT_STREAM_HPP_INCLUDED
#define UAVCAN_MARSHAL_BIT_STREAM_HPP_INCLUDED

#include <cassert>
#include <uavcan/std.hpp>
#include <uavcan/util/templates.hpp>
#include <uavcan/transport/abstract_transfer_buffer.hpp>
#include <uavcan/build_config.hpp>

namespace uavcan
{
void bitarrayCopy(const unsigned char* src_org, std::size_t src_offset, std::size_t src_len,
                  unsigned char* dst_org, std::size_t dst_offset);

class UAVCAN_EXPORT BitStream
{
    static const unsigned MaxBytesPerRW = 16;

    ITransferBuffer& buf_;
    unsigned bit_offset_;
    uint8_t byte_cache_;

    static inline unsigned bitlenToBytelen(unsigned bits) { return (bits + 7) / 8; }

    static inline void copyBitArrayAlignedToUnaligned(const uint8_t* src_org, unsigned src_len,
                                                      uint8_t* dst_org, unsigned dst_offset)
    {
        bitarrayCopy(reinterpret_cast<const unsigned char*>(src_org), 0, src_len,
                     reinterpret_cast<unsigned char*>(dst_org), dst_offset);
    }

    static inline void copyBitArrayUnalignedToAligned(const uint8_t* src_org, unsigned src_offset, unsigned src_len,
                                                      uint8_t* dst_org)
    {
        bitarrayCopy(reinterpret_cast<const unsigned char*>(src_org), src_offset, src_len,
                     reinterpret_cast<unsigned char*>(dst_org), 0);
    }

public:
    static const unsigned MaxBitsPerRW = MaxBytesPerRW * 8;

    enum
    {
        ResultOutOfBuffer = 0,
        ResultOk          = 1
    };

    explicit BitStream(ITransferBuffer& buf)
        : buf_(buf)
        , bit_offset_(0)
        , byte_cache_(0)
    {
        StaticAssert<sizeof(uint8_t) == 1>::check();
    }

    int write(const uint8_t* bytes, const unsigned bitlen);
    int read(uint8_t* bytes, const unsigned bitlen);

#if UAVCAN_TOSTRING
    std::string toString() const;
#endif
};

}

#endif // UAVCAN_MARSHAL_BIT_STREAM_HPP_INCLUDED