C写选项
发布时间:2020-12-16 07:16:08 所属栏目:百科 来源:网络整理
导读:我正在尝试使用std :: ofstream打开文件进行写入,我想将其设置为直写模式(即使用CreateFile Win API提供的“FILE_FLAG_WRITE_THROUGH”). 有没有一些STL方式来实现它? 我不想基于WinAPI编写代码. 我的目标是禁用OS缓存并使用不同的块大小执行写入,以获得与
我正在尝试使用std :: ofstream打开文件进行写入,我想将其设置为直写模式(即使用CreateFile Win API提供的“FILE_FLAG_WRITE_THROUGH”).
有没有一些STL方式来实现它? @Update #include <cstdlib> #include <fstream> #include <iostream> #include <vector> #include <ctime> std::vector<unsigned char> GenerateRandomData(long numBytes) { std::vector<unsigned char> res(numBytes); std::srand(std::time(0)); for (int i = 0; i < numBytes; ++i) res[i] = static_cast<unsigned char>(std::rand() % 256); return res; } int main(int,char) { // generate random data const long dataLength = 1 * 1024 * 1024 * 1024; // 3 GB std::vector<unsigned char> outbuf = GenerateRandomData(dataLength); // define I/O block size ( const auto blk_size = 128 * 1024; // 128K char blk[blk_size]; // configure output stream std::ofstream ofs; ofs.rdbuf()->pubsetbuf(blk,blk_size); ofs.setf(std::ios_base::unitbuf); // open file to write ofs.open("output.dat",std::ofstream::binary | std::ofstream::trunc); // write all data performing 512K I/O Operations auto ptr_idx = 0; auto ptr = reinterpret_cast<char*>(outbuf.data()); const auto outbuf_size = outbuf.size(); std::clock_t sw = clock(); ofs.write((const char *)&ptr[ptr_idx],outbuf_size); ofs.flush(); ofs.close(); sw = ( clock() - sw ); double writtenBytes = static_cast<double>(outbuf.size()); double writtenMBytes = writtenBytes / (1024 * 1024); double testSeconds = static_cast<double>(sw) / static_cast<double>(CLOCKS_PER_SEC); double avgSpeed = writtenMBytes / testSeconds; std::cout << "Benchmark: written " << writtenMBytes << " MB in " << testSeconds << " sec. => " << avgSpeed << "MB/s" << std::endl; std::getchar(); return 0; } 先感谢您 解决方法
使用:std :: unitbuf
std::ofstream outfile ("file.txt"); outfile << std::unitbuf << "Hellon"; // immediately flushed (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |