C++ Exactly copying the contents of a file

Question

As part of an encryption project I am making for fun, I would like to take the contents, of a file, be it PDF, DOCX, JPEG, any ASCII file, play around with the characters numerically and then reverse the process at the end to give a file of the original file type which can be opened etc. as normal.

First, as I test I thought that I would read the contents of a .docx file into a string, and then write that straight to another .docx file with a different name. However, when this is done, Microsoft Word refuses to open the file: "The file is corrupted and cannot be opened".

Here is the code I used to copy the file:

#include <iostream>
#include <fstream>
using namespace std;

int main()
{
    ifstream inputFile("C:\\Users\\MyUser\\Documents\\This is a test.docx", ios::in | ios::binary);
    inputFile.seekg(0, ios::end);
    int length = inputFile.tellg();
    inputFile.seekg(0, ios::beg);
    string fileContents;
    fileContents.resize(length);
    inputFile.read(&fileContents[0], length);
    inputFile.close();

    ofstream outputFile("C:\\Users\\MyUser\\Documents\\TestCopy.docx", ios::app);
    outputFile.write(&fileContents[0], length);
    outputFile.close();


    cout << "Complete.";
    int n;
    cin >> n; //Keeps the program open so message can be read.
}

What is the problem and how can the program be edited to give a valid file?

Cheers in advance.

Answer 1

您的输出流不是二进制模式。

Answer 2

看起来您忘了为输出文件（ios :: binary）设置二进制标志。