arcgis 紧凑瓦片解析

  bool pie_datasource_bundle_readTile(const std::string &bundleFilePath, long long offset,
                                        std::unique_ptr<char[]> &byteArray, int &arrayCount) {

        std::ifstream in_stream;
        in_stream.open(bundleFilePath, std::ios::in | std::ios::binary);
        if (in_stream.is_open()) {
            //切片长度 数据
            char data_buffer[4]{0};
            //从文件头，跳过offset字节
            in_stream.seekg(offset, std::ios_base::beg);
            //读取块长度
            if (in_stream.read(data_buffer, sizeof(char) * 4).eof())//如果包含到结尾则返回失败
            {
                in_stream.close();
                return false;
            }
            //数据块长度
            int blobSize = 0;
            blobSize=(int)(data_buffer[0]&0xff)
            +(int)(data_buffer[1]&0xff)*256
            +(int)(data_buffer[2]&0xff)*65536
            +(int)(data_buffer[3]&0xff)*16777216;
            if (blobSize <= 0) {
                in_stream.close();
                return false;
            }
            arrayCount = blobSize;
            byteArray = std::unique_ptr<char[]>(new char[arrayCount]);
            if (in_stream.read(byteArray.get(), arrayCount).eof())//如果包含到结尾则返回失败
            {
                in_stream.close();
                return false;
            }
            in_stream.close();
            return true;
        }
        return false;
    }

bool pie_datasource_bundle_readTileFromBundleV1(const std::string &bundleFilePath, const std::string &bundlxFilePath,
                                                    int index, std::unique_ptr<char[]> &byteArray, int &arrayCount) {
        //索引数据 长度
        char buffer[5]{0};
        std::ifstream in_stream;
        in_stream.open(bundlxFilePath, std::ios::in | std::ios::binary);
        if (in_stream.is_open()) {
            //从文件头，跳过bundlx的前16字节，并移动到index个块的位置，每个块长度为5字节
            in_stream.seekg(16 + 5 * index, std::ios_base::beg);
            //读取块所在偏移量
            if (in_stream.read(buffer, sizeof(char) * 5).eof())//如果包含到结尾则返回失败
            {
                in_stream.close();
                return false;
            }
            in_stream.close();
            long long offset = 0;
            offset=(long long)(buffer[0]&0xff)
            +(long long)(buffer[1]&0xff)*256
            +(long long)(buffer[2]&0xff)*65536
            +(long long)(buffer[3]&0xff)*16777216
            +(long long)(buffer[4]&0xff)*4294967296L;
            return pie_datasource_bundle_readTile(bundleFilePath, offset, byteArray, arrayCount);
        }
        return false;
    }

    bool pie_datasource_bundle_readTileFromBundleV2(const std::string &bundleFilePath, int index,
                                                    std::unique_ptr<char[]> &byteArray, int &arrayCount) {
        //索引数据 长度
        char buffer[4]{0};
        std::ifstream in_stream;
        in_stream.open(bundleFilePath, std::ios::in | std::ios::binary);
        if (in_stream.is_open()) {
            //从文件头，跳过bundle的前64字节，并移动到index个块的位置，每个块长度为8字节
            in_stream.seekg(64 + 8 * index, std::ios_base::beg);
            //读取块所在偏移量
            if (in_stream.read(buffer, sizeof(char) * 4).eof())//如果包含到结尾则返回失败
            {
                in_stream.close();
                return false;
            }
            in_stream.close();
            int offset = 0;
            offset=(int)(buffer[0]&0xff)
            +(int)(buffer[1]&0xff)*256
            +(int)(buffer[2]&0xff)*65536
            +(int)(buffer[3]&0xff)*16777216;//长度偏移量
            auto lengthoffset = offset - 4;
            return pie_datasource_bundle_readTile(bundleFilePath, lengthoffset, byteArray, arrayCount);
        }
        return false;
    }