c++ - 将 '3d' vector Pod 类型写入二进制文件 C++

Question

我做了下面的示例代码(用-std=c++11编译)

这是一个 10*20*30 的 3d vector ，到处都是数字 8。我不知道如何将它写入磁盘并读回。谁能告诉我如何完成 r-rw 例程？

#include <iostream>
#include <vector>
#include <fstream>

int main(int argc, char *argv[])
{
    //'3d' vector filled with 8's
    std::vector<std::vector<std::vector<int>>>  all8s (10,std::vector<std::vector<int>>(20,std::vector <int>(30,8)));;
    //print the whole
    std::cout << "1st size " << all8s.size() << " \n";
    for ( auto& elemTop : all8s ) {
        std::cout << "2nd size " << elemTop.size() << " \n";
        for ( auto& elemMiddle : elemTop ) {
            std::cout << "3th size " << elemMiddle.size() << "  \n";
            for ( auto& elemBottom : elemMiddle ){
                std::cout << elemBottom << ",";
            }
            std::cout << "\n";
        }
    }

    //write binary file
    std::ofstream out("all8s.bin", std::ios::out | std::ios::binary);
    //how do I write this to disk
    out.close();

    //read it?
    std::vector<std::vector<std::vector<int>>>  all8sReloaded;
    std::ifstream in("all8s.bin", std::ios::in | std::ios::binary);
    //how to read it back?
    in.close();
}

Answer 1

不可能在一个写语句中写完所有的 block 。根据您的代码，一个非常简单的解决方案是:

for ( auto& elemTop : all8s )
        for ( auto& elemMiddle : elemTop )
            for ( auto& elemBottom : elemMiddle )
                cout.write (reinterpret_cast(const char*)&elemBottom, sizeof(int));

另一方面，如果您想阅读它们，则需要知道 vector 的维度；它是相似的。否则，您必须在数据之前保存此尺寸。