[C/C++/Qt] 正确使用C++快速写入大文件

复制代码
#include <iostream>
#include <fstream>
#include <vector>

const int BUFFER_SIZE = 8192; // 缓冲区大小

void writeToFile(const std::string& fileName, const std::vector<char>& data) {
    std::ofstream file(fileName, std::ios::binary);
    file.write(data.data(), data.size());
    file.close();
}

int main() {
    std::vector<char> buffer(BUFFER_SIZE, 'A'); // 填充缓冲区数据

    std::string fileName = "largeFile.txt";
    std::vector<char> data;

    int fileSize = 1024 * 1024 * 100; // 100MB
    int totalBufferSize = 0;

    std::ofstream file(fileName, std::ios::binary);

    while (totalBufferSize < fileSize) {
        int bufferSize = std::min(fileSize - totalBufferSize, BUFFER_SIZE);
        file.write(buffer.data(), bufferSize);
        totalBufferSize += bufferSize;
    }

    file.close();
    std::cout << "大文件写入完成" << std::endl;
    return 0;
}

复制代码
#include <iostream>
#include <boost/interprocess/file_mapping.hpp>
#include <boost/interprocess/mapped_region.hpp>

int main() {
    std::string fileName = "largeFile.txt";
    std::size_t fileSize = 1024 * 1024 * 100; // 100MB
    
    boost::interprocess::file_mapping::remove(fileName.c_str()); // 删除已存在的文件
    
    // 创建新文件
    boost::interprocess::file_mapping file(fileName.c_str(), boost::interprocess::read_write);
    boost::interprocess::mapped_region region(file, boost::interprocess::read_write, 0, fileSize);
    
    // 在内存中操作文件内容
    char* addr = static_cast<char*>(region.get_address());
    std::fill_n(addr, fileSize, 'A'); // 填充文件内容为'A'
    
    std::cout << "大文件写入完成" << std::endl;
    
    return 0;
}