ADU.h

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#pragma once

#include "PDU.h"
#include "../Error.h"

namespace IO
{
namespace Modbus
{
// Buffer to construct RTU requests and process responses
struct ADU {
    static constexpr uint8_t BROADCAST_ADDRESS{0x00};
    static constexpr size_t MinSize{4};
    static constexpr size_t MaxSize{256};

    union {
        struct {
            uint8_t slaveAddress;
            PDU pdu;
        };
        uint8_t buffer[MaxSize];
    };

    size_t prepareRequest();
    size_t prepareResponse();
    ErrorCode parseRequest(size_t receivedSize);
    ErrorCode parseResponse(size_t receivedSize);
private:
    size_t preparePacket(size_t pduSize);
    ErrorCode parsePacket(size_t receivedSize, size_t pduSize);
};

static_assert(offsetof(ADU, pdu) == 1, "ADU alignment error");

} // namespace Modbus
} // namespace IO