read and write string in binary file

Question

0.00/5 (No votes)

See more:

I write this program for learning write and read string in binary file.

C++

// testtest.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int main( )
{
	string str1 = "abababab";
	string str2 = "wjwjwjwjwjwj";
	string str3 = "vivivivivivivivi";

	int size1 = (str1.size());
	int size2 = (str2.size());
	int size3 = (str3.size());

	ofstream output ("output.txt", ios::out | ios::binary);
	if (!output)
	{
		cout << "can't open file" << endl;
		exit(1);
	}

	output.write(reinterpret_cast<char *>(&size1), sizeof(int));
	output.write(str1.c_str(), size1);

	output.write(reinterpret_cast<char *>(&size2), sizeof(int));
	output.write(str2.c_str(), size2);

	output.write(reinterpret_cast<char *>(&size3), sizeof(int));
	output.write(str3.c_str(), size3);

	str1 = str2 = str3 = "";
	size1 = size2 = size3 = 0;

	output.flush();
	output.close();
	//=======================================================================
	ifstream input("output.txt", ios::in | ios::binary);
	if (!output)
	{
		cout << "can't open file" << endl;
		exit(1);
	}

	input.read(reinterpret_cast<char *>(&size1), sizeof(int));
	input.read(reinterpret_cast<char *>(&str1), size1);

	input.read(reinterpret_cast<char *>(&size2), sizeof(int));
	input.read(reinterpret_cast<char *>(&str2), size2);

	input.read(reinterpret_cast<char *>(&size3), sizeof(int));
	input.read(reinterpret_cast<char *>(&str3), size3);

	cout << str1 << endl << str2 << endl << str3 << endl << endl;

	return 0;
}

program read str1 and str2 correctly but can't read str3 . visual c++ return these messages when I debug program:

Unhandled exception at 0x51EDA9E8 (msvcr120d.dll) in testtest.exe: 0xC0000005: Access violation reading location 0x6976696A.

and

str3: Error reading characters of string

Posted 19-Mar-15 21:22pm

farhad bat

Updated 19-Mar-15 21:36pm

v3

Add a Solution

Comments

Timberbird 20-Mar-15 5:23am

Your code seems a bit strange - do you really intend to read std::string object in file, not the string (char*) itself? When you read like
input.read(reinterpret_cast<char *="">(&str3), size3);
, it's not like "take size3 bytes from file and place them into string str3", it's "read size3 bytes from file and place them into memory, starting with address &str3". You may occasionally corrupt memory state this way. I suggest you try to read into buffer variable (char*) and them assign its value to std::string objects.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

farhad bat · Accepted Answer · 2015-03-19T23:14:00

I solve it

C++

// testtest.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int main( )
{
	char *buf;
	string str1 = "abababab";
	string str2 = "wjwjwjwjwjwj";
	string str3 = "vivivivivivivivi";

	int size1 = (str1.size());
	int size2 = (str2.size());
	int size3 = (str3.size());

	ofstream output ("output.txt", ios::out | ios::binary);
	if (!output)
	{
		cout << "can't open file" << endl;
		exit(1);
	}

	output.write(reinterpret_cast<char *>(&size1), sizeof(int));
	output.write(str1.c_str(), size1);

	output.write(reinterpret_cast<char *>(&size2), sizeof(int));
	output.write(str2.c_str(), size2);

	output.write(reinterpret_cast<char *>(&size3), sizeof(int));
	output.write(str3.c_str(), size3);

	str1 = str2 = str3 = "";
	size1 = size2 = size3 = 0;

	output.flush();
	output.close();
	//=======================================================================
	ifstream input("output.txt", ios::in | ios::binary);
	if (!output)
	{
		cout << "can't open file" << endl;
		exit(1);
	}

	input.read(reinterpret_cast<char *>(&size1), sizeof(int));
	buf = new char[size1];
	input.read( buf, size1);
	str1 = "";
	str1.append(buf, size1);

	input.read(reinterpret_cast<char *>(&size2), sizeof(int));
	buf = new char[size2];
	input.read(buf, size2);
	str2 = "";
	str2.append(buf, size2);

	input.read(reinterpret_cast<char *>(&size3), sizeof(int));
	buf = new char[size3];
	input.read(buf, size3);
	str3 = "";
	str3.append(buf, size3);

	cout << str1 << endl << str2 << endl << str3 << endl << endl;

	return 0;
}