Binary File: Writing and Reading

[jennjgo]

Hi!
^.^
I am making a program but I can't continue because there's something wrong...

#include<iostream>
#include<string>
#include<fstream>
 
using namespace std;
 
struct record{
  int IdentificationNumber;
  string Name;
  int Quantity;
  double Cost;
};
 
main(){
  record TheTool;
  fstream file("hardware.dat", ios::in|ios::out|ios::binary);
  if(!file){
    cerr<<"File could not be opened or created"<<endl;
    exit(1);    
  }
  cout<<"I Will Add Something To The File"<<endl;
  cout<<"Enter tool ID Number: ";
  cin>>TheTool.IdentificationNumber;
  cout<<"Enter tool name: ";
  cin.ignore();
  getline(cin, TheTool.Name);
  cout<<"Enter Quantity: ";
  cin>>TheTool.Quantity;
  cout<<"Enter Cost: ";
  cin>>TheTool.Cost;
  file.seekp((TheTool.IdentificationNumber-1)*sizeof(record));
  file.write(reinterpret_cast<const char *> (&TheTool), sizeof(record));
  file.close();
  fstream file1("hardware.dat", ios::in|ios::out|ios::binary);
  file1.seekg(0);
  file1.read(reinterpret_cast<char*>(&TheTool),sizeof(record));
  while(file1.good()){
    cout<<TheTool.IdentificationNumber<<TheTool.Name<<TheTool.Quantity<<TheTool.Cost<<endl;
    file1.read(reinterpret_cast<char*>(&TheTool),sizeof(record));
  }
}

I want to save it to a binary file and if I exit the program and I open it again, the previous input will still be there. But when I run the program the second time, and read its contents, the name of the tool is replaced with my new input and I don't know why or how to stop this from happening. Also, when the tool identification number is 1,2,3,... (input in proper order), it reads ok(except the name) and runs until it reaches its end. But when the number is in 1,2,3,5 (there's no 4 so not in proper order of input), it will encountered an error. But I want to be able to do that. Please help... Thanks!

(Sorry for the wrong grammar and not nice explanation, i'm not good in english hehe.. thank you!)

[weaknessforcats]

You are reading and writing sizeof(record).

Are you saying that arecord object with an name of:

ADADADADADADADADADADADADDADADADADADADDADADADADADA

is the same size as a record object with a name of

A

???

Your string member probably as the string data on the heap so writing the sizeof(record) just writes the part of the string that's on the stack.

You need to prepare a data buffer that contains all of the member data in a format where the number of bytes is constant. Then read/write the sizeof that buffer.

On the read, you will need to parse the buffer back into a record object.