C++读写文本文件

文件内容

读取文件

• 先打开文件，按行读取
• 对每行数据按空格分割
• 格式转换

#include <iostream>
#include <memory>
#include <vector>
#include <fstream>
#include <sstream>

void preprocess(std::string dataPath) {
	std::fstream infile;
	infile.open(dataPath, std::ios::in);   // 打开文件
	if (!infile.is_open()) {
		std::cout << "open file " << dataPath << " failed! " << std::endl;
		return;
	}
	std::vector<std::string> data;
	std::string s;
	while (std::getline(infile, s)) {     // 按行读取
		data.push_back(s);
	}

	std::vector<std::vector<float> > points;
	std::string suffix = dataPath.substr(dataPath.find_last_of('.') + 1);   // 获取文件类型
	if (suffix == "txt") {
		for (int i = 0; i < data.size(); ++i) {
			std::vector<float> line_data;
			std::istringstream ss(data[i]);
			std::string item;
			int n = 0;
			while (n <3 && ss >> item) {                           // 按空格分割并对相应数据进行格式转换
				line_data.push_back(std::stof(item));
				n += 1;
			}
			points.push_back(line_data);
		}
	}
	else if (suffix == "pcd"){
		int skipRows = 10;
		for (int i = skipRows; i < data.size(); ++i) {
			std::vector<float> line_data;
			std::istringstream ss(data[i]);
			std::string item;
			int n = 0;
			while (n <3 && ss >> item) {
				line_data.push_back(std::stof(item));
				n += 1;
			}
			points.push_back(line_data);
		}
	}
	else {
		std::cout << "Don't support file type, just useful for txt or pcd!";
		return;
	}
}

写入文件

std::vector<std::vector<float> >resPts;
std::fstream outfile;
outfile.open("D:/Debug_dir/res.pts", std::ios::out);
if (!outfile.is_open()) {
    std::cout << "write res to file is failed! " << std::endl;
    return false;
}
for (auto pt : resPts) {
    outfile << pt[0] << " " << pt[1] << " " << pt[2] << "\n";
}
outfile.close();