顺序读取从二进制文件结构中的C ++ [英] sequentially reading a structs from binary file in C++

问题描述

我想编写一个程序，该程序执行操作时，
（实施例：搜索，更新，或添加），它应该是直接访问。该程序
不应该读所有的记录顺序将达到创纪录。

I'm trying to write a program, when the program is performing an operation (Example: search, update, or add), it should be direct access. The program should not read all the records sequentially to reach a record.

 #include <iostream>
#include <fstream>
#include <string>

using namespace std;

struct Student{
    int Id;
    int Money;
    int Age;
    char name[15];
};

void main(){
    Student buffer;
    ofstream BinaryFile("student", ios::binary);
    ifstream WorkerText("worker.txt");

//-------------------------------------------------------------------------------------------------------------
    while( WorkerText.good() ){                     
        WorkerText>> buffer.Age >> buffer.name >> buffer.name >> buffer.name;
        BinaryFile.write(  (char *) &buffer, sizeof(Student)  );    

    }
    BinaryFile.close();
//-------------------------------------------------------------------------------------------------------------
    ifstream ReadBinary( "student", ios::binary | ios::out );
    while( BinaryFile.good() ){                     
        ReadBinary.read((char*)&buffer,sizeof(Student));
        cout<<buffer.Age;

    }


//-------------------------------------------------------------------------------------------------------------


system("pause");
}

我stucked在这里我不能按顺序读取我怎么能解决这个问题。

I stucked here I could not read sequentially how can I solve this

推荐答案

如果该文件包含相同尺寸的结构，或使用一些索引表。可以跳过顺序只读

You can skip sequential read only if the file contains structures of the same size, or uses some index table.

有关大小相同的结构的情况下：

For the case of structures of same size:

void ReadStudent(istream &src, Student &dst)
{
    src.read(&dst, sizeof(dst));
}

void GoToStudentIndex(istream &src, size_t idx)
{
   src.seekg(idx * sizeof(Student), is.beg);
 }

上面的函数假设你正在写数据如下：

The functions above assume you are writing data as follows:

void WriteStudent(ostream &dst, const Student &src)
{
    dst.write(&src, sizeof(src));
}

这篇关于顺序读取从二进制文件结构中的C ++的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！