点云读取加速c++ ASCii 模式ply 或者txt

相较于Qt Qtextstream的性能提升十倍！！！！！！！！
本文点云格式特殊 有需要自行修改即可

    QFile dataFile(fileName);
    bool ret = dataFile.open(QIODevice::ReadOnly|QIODevice::Text);
    if(ret)
    {
		
		uchar* fpr = dataFile.map(0, dataFile.size());
		int cnt = 0;
		int subcnt = 0;
		char *substr;
		char *s = strdup((char*)fpr);
		
		//切换到element vertex 行
		substr = mystrsep(&s, "\n");
		substr = mystrsep(&s, "\n");
		substr = mystrsep(&s, "\n");
		substr = mystrsep(&s, "\n");

		//分割出数字
		char *lineSubStr;
		int total_num = 0;
		while (subcnt < 3)
		{
			lineSubStr = mystrsep(&substr, " ");		
			if(subcnt ==2)
				total_num = atof(lineSubStr);
			subcnt++;
		}
		//分配点内存
		std::vector<std::vector<float>>temp_points(total_num, {0,0,0,0,0,0,0,0,0});
		for(int i=0;i<11;i++)
		substr = mystrsep(&s, "\n");

		//读取内容		
		for (int i = 0; i < total_num; i++)
		{
			substr = mystrsep(&s, "\n");
			for (int j = 0; j < 9; j++)
			{
				lineSubStr = mystrsep(&substr, " ");
				temp_points[i][j] = atof(lineSubStr);
			}
		}

参考https://blog.csdn.net/aifei1924/article/details/102263896?ops_request_misc=&request_id=&biz_id=102&utm_term=qt%20%E5%A4%9A%E7%BA%BF%E7%A8%8B%E8%AF%BB%E5%8F%96%E7%82%B9%E4%BA%91&utm_medium=distribute.pc_search_result.none-task-blog-2_allsobaiduweb~default-0-102263896.142^v5pc_search_quality_down,157^v4control&spm=1018.2226.3001.4187