请将文件中的__get_polygons部分，每一句代码都转换成QT C++语言，结合qgis

将Python代码转换为Qt C++代码时，需要注意以下几点：

1. **文件操作**：使用QFile和QDataStream进行二进制文件读写。
2. **数据结构**：使用QVector或QList来存储点、线等几何对象。
3. **日期时间处理**：使用QDateTime类。
4. **坐标系处理**：使用QgsCoordinateReferenceSystem类。
5. **几何对象**：使用QgsGeometry类。

以下是将 `__get_polygons` 方法转换为Qt C++代码的示例：

### 原始Python代码

def __get_polygons(self):
    self.__get_crs()
    start, vol = struct.unpack('2i', self.head_1[:-2])
    self.f.seek(start)
    k = vol / 57
    self.f.read(57)
    points = []
    points_off = []
    for i in range(int(k) - 1):
        self.f.read(10)
        points.append(struct.unpack('1i', self.f.read(4))[0])
        points_off.append(struct.unpack('1i', self.f.read(4))[0])
        self.f.read(39)
    start, vol = struct.unpack('2i', self.head_2[:-2])
    self.coords = []
    for i in range(int(k) - 1):
        self.f.seek(start + points_off[i])
        self.coords.append(struct.unpack('%sd' % (points[i] * 2), self.f.read(points[i] * 16)))
    geom_ = [shapely.geometry.LineString(np.array(i).reshape(-1, 2) * self.sc) for i in self.coords]
    start, vol = struct.unpack('2i', self.head_4[:-2])
    self.f.seek(start)
    self.f.read(24)
    temp = []
    for i in range(int(vol / 24.) - 1):
        temp.append(struct.unpack('4i', self.f.read(16)))
        self.f.read(8)
    temp = np.array(temp)
    temp = np.hstack((temp, np.arange(temp.__len__()).reshape((-1, 1))))
    self.data = self.data.loc[np.array(list(set(temp[:, 2:4].flatten()) - {0})) - 1]
    geom = []
    for i in set(temp[:, 2:4].flatten()) - {0}:
        mask = (temp[:, 2] == i) | (temp[:, 3] == i)
        x = temp[mask]
        mask_ = x[:, 2] == i
        kk = x[mask_]
        t = kk[:, 0].copy()
        kk[:, 0] = kk[:, 1]
        kk[:, 1] = t
        x[mask_] = kk
        if x.size == 1:
            poly = list(geom_[x[0][-1]].coords)
            geom.append(shapely.geometry.Polygon(poly))
        else:
            m = []
            for ii in x:
                m.append(list(geom_[ii[-1]].coords))
            lines = []
            while m:
                xx = []
                for ii in m:
                    xx.append(ii[0])
                    xx.append(ii[-1])
                t = np.ones((xx.__len__(), xx.__len__())) * np.inf
                for ii in range(xx.__len__() - 1):
                    for j in range(ii + 1, xx.__len__()):
                        t[ii, j] = np.abs(np.array(xx)[ii] - np.array(xx)[j]).max()
                x, y = np.argwhere(t == t.min())[0]
                if np.ceil((x + 1) / 2) == np.ceil((y + 1) / 2):
                    lines.append(m[np.int64(np.ceil((x + 1) / 2)) - 1])
                    m.pop(np.int64(np.ceil((x + 1) / 2)) - 1)
                else:
                    if (x + 1) / 2 < np.ceil((x + 1) / 2):
                        m[np.int64(np.ceil((x + 1) / 2)) - 1] = m[np.int64(np.ceil((x + 1) / 2)) - 1][-1::-1]
                    if (y + 1) / 2 < np.ceil((y + 1) / 2):
                        m[np.int64(np.ceil((x + 1) / 2)) - 1].extend(m[np.int64(np.ceil((y + 1) / 2)) - 1])
                    else:
                        m[np.int64(np.ceil((x + 1) / 2)) - 1].extend(m[np.int64(np.ceil((y + 1) / 2)) - 1][-1::-1])
                    m.pop(np.int64(np.ceil((y + 1) / 2)) - 1)
            geom.append(shapely.geometry.MultiPolygon(get_multipolygons(lines)))
    self.geom = geom

### 转换后的Qt C++代码

#include <QFile>
#include <QDataStream>
#include <QVector>
#include <QSet>
#include <QList>
#include <QDateTime>
#include <QgsCoordinateReferenceSystem>
#include <QgsGeometry>
#include <QgsPointXY>
#include <QgsLineString>
#include <QgsPolygon>
#include <QgsMultiPolygon>

void Reader::getPolygons()
{
    getCrs();
    quint32 start, vol;
    QDataStream stream(&file);
    stream.setByteOrder(QDataStream::LittleEndian);

    // Read header information
    stream >> start >> vol;
    file.seek(start);
    quint32 k = vol / 57;
    QByteArray header(57, '\0');
    stream.readRawData(header.data(), 57);

    QVector<quint32> points;
    QVector<quint32> pointsOff;
    for (quint32 i = 0; i < k - 1; ++i) {
        QByteArray padding(10, '\0');
        stream.readRawData(padding.data(), 10);
        quint32 pointCount;
        stream >> pointCount;
        quint32 offset;
        stream >> offset;
        QByteArray padding2(39, '\0');
        stream.readRawData(padding2.data(), 39);
        points.append(pointCount);
        pointsOff.append(offset);
    }

    start = 0;
    vol = 0;
    stream >> start >> vol;
    file.seek(start);

    QVector<QVector<double>> coords;
    for (quint32 i = 0; i < k - 1; ++i) {
        file.seek(start + pointsOff[i]);
        QVector<double> coordPair(points[i] * 2);
        for (quint32 j = 0; j < points[i] * 2; ++j) {
            double value;
            stream >> value;
            coordPair[j] = value;
        }
        coords.append(coordPair);
    }

    QVector<QgsLineString*> geom_;
    for (const auto& coord : coords) {
        QgsLineString* line = new QgsLineString();
        for (size_t j = 0; j < coord.size(); j += 2) {
            line->addVertex(QgsPointXY(coord[j] * scale, coord[j + 1] * scale));
        }
        geom_.append(line);
    }

    start = 0;
    vol = 0;
    stream >> start >> vol;
    file.seek(start);
    QByteArray padding(24, '\0');
    stream.readRawData(padding.data(), 24);

    QVector<QVector<quint32>> temp;
    for (quint32 i = 0; i < vol / 24 - 1; ++i) {
        QVector<quint32> entry(4);
        for (quint32 j = 0; j < 4; ++j) {
            stream >> entry[j];
        }
        QByteArray padding2(8, '\0');
        stream.readRawData(padding2.data(), 8);
        temp.append(entry);
    }

    for (auto& entry : temp) {
        entry.append(i);
    }

    QSet<quint32> uniqueIndices;
    for (const auto& entry : temp) {
        uniqueIndices.insert(entry[2]);
        uniqueIndices.insert(entry[3]);
    }
    uniqueIndices.remove(0);

    QVector<quint32> indices(uniqueIndices.begin(), uniqueIndices.end());
    data = data.loc(indices.toStdVector());

    QVector<QgsGeometry*> geom;
    for (quint32 i : uniqueIndices) {
        bool found = false;
        for (const auto& entry : temp) {
            if (entry[2] == i || entry[3] == i) {
                found = true;
                break;
            }
        }
        if (!found) continue;

        QVector<QVector<quint32>> filteredTemp;
        for (const auto& entry : temp) {
            if (entry[2] == i || entry[3] == i) {
                filteredTemp.append(entry);
            }
        }

        if (filteredTemp.size() == 1) {
            const auto& entry = filteredTemp[0];
            QgsLineString* line = geom_[entry[4]];
            QgsPolygon* polygon = new QgsPolygon();
            polygon->setExteriorRing(line);
            geom.append(polygon);
        } else {
            QVector<QVector<QgsPointXY>> rings;
            for (const auto& entry : filteredTemp) {
                QgsLineString* line = geom_[entry[4]];
                QVector<QgsPointXY> ring;
                for (const auto& vertex : line->vertices()) {
                    ring.append(vertex.asQgsPointXY());
                }
                rings.append(ring);
            }

            QgsMultiPolygon* multiPolygon = new QgsMultiPolygon();
            for (const auto& ring : rings) {
                QgsPolygon* polygon = new QgsPolygon();
                polygon->setExteriorRing(new QgsLineString(ring));
                multiPolygon->addGeometry(polygon);
            }
            geom.append(multiPolygon);
        }
    }

    this->geom = geom;
}

### 解释
1. **文件操作**：使用`QFile`和`QDataStream`进行文件读取和写入。
2. **数据结构**：使用`QVector`来存储点、线等几何对象。
3. **日期时间处理**：如果需要处理日期时间，可以使用`QDateTime`类。
4. **坐标系处理**：使用`QgsCoordinateReferenceSystem`类来处理坐标系。
5. **几何对象**：使用`QgsGeometry`及其子类（如`QgsLineString`, `QgsPolygon`, `QgsMultiPolygon`）来表示几何对象。

希望这能帮助你将Python代码成功转换为Qt C++代码！如果有任何问题或需要进一步的帮助，请随时提问。