シリアルポートの16進数を処理したい

//コマンド格納クラス
class CivCommand {
public:
    unsigned char ReceiverAddress;//受信アドレス
    unsigned char SenderAddress;//送信アドレス
    unsigned char Command;//コマンド
    unsigned char SubCommand;//サブコマンド
    unsigned short SubSubCommand;//サブサブコマンド(コマンド0x1Aのみで使用)
    std::vecter<unsigned char> datas;//データエリア
    unsigned int ByteLength;//データ長(プリアンブル、ポストアンブルも含む)

    //コンストラクタ
    //  buffer: 受信バッファ
    //  bufferMaxLength:  受信バッファの最大サイズ
    CivCommand(const unsigned char *buffer, size_t bufferMaxLength) {
        //簡易フォーマットチェック
        if (buffer[0] != 0xFE || buffer[1] != 0xFE) {
            throw "プリアンブル異常";
        }
        unsigned char* postamblePointer = memchr(buffer + 5, 0xFD, bufferMaxLength - 5);
        if (postamblePointer == NULL) {
            throw "ポストアンブル未検出";
        }

        //ヘッダ部取得
        ByteLength = postamblePointer - buffer + 1;
        ReceiverAddress = buffer[2];
        SenderAddress = buffer[3];
        Command = buffer[4];
        int dataHeadIndex = 5;
        if (Command <= 0x06 || Command == 0x09 || Command == 0x0A || Command == 0x0B ||
            Command == 0x10 || Command == 0x11 || Command == 0x17 || Command == 0x25 ||
            Command == 0x26) {
            //サブコマンドなし
        } else if (Command == 0x0E || Command == 0x0F || Command == 0x13 || Command == 0x14 ||
            Command == 0x15 || Command == 0x16 || Command == 0x18 || Command == 0x19 ||
            Command == 0x1B || Command == 0x1C || Command == 0x1E || Command == 0x21 ||
            Command == 0x25 || Command == 0x26 || Command == 0x27 || Command == 0x28) {
            //サブコマンドあり(0x1A以外)
            SubCommand = buffer[5];
            dataHeadIndex = 6;
        } else if (Command == 0x1A) {
            //サブサブコマンドあり(0x1Aのみ)
            SubCommand = buffer[5];
            SubSubCommand = (buffer[6] << 8) + buffer[7];
            dataHeadIndex = 8;
        } else {
            throw "未定義コマンド";
        }

        //データ部をクラスの内部バッファにコピー
        datas.reserve(ByteLength - dataHeadIndex - 1);
        for (int i=dataHeadIndex; i < ByteLength-1; i++) {
            datas.push_back(buffer[i]);
        }
    }
}