Reading Binary Files w/ ifstream

Question

I'm trying to read in an .exe and write it back out. My code works with .txt files but for some reason it is breaking executables. What am I doing wrong? I'm not sure if I am reading it wrong or writing it wrong..

#include <string>
#include <vector>
#include <iostream>
#include <filesystem>
#include <unordered_set>

#include <Windows.h>

unsigned char *ReadFileAsBytes(std::string filepath, DWORD &buffer_len)
{
    std::ifstream ifs(filepath, std::ofstream::binary | std::ifstream::ate);
    if (!ifs.is_open())
    {
        return(nullptr);
    }

    // Go To End
    ifs.seekg(0, ifs.end);

    // Get Position (Size)
    buffer_len = static_cast<DWORD>(ifs.tellg());

    // Go To Beginning
    ifs.seekg(0, ifs.beg);

    // Allocate New Char Buffer The Size Of File
    PBYTE buffer = new BYTE[buffer_len];

    ifs.read(reinterpret_cast<char*>(buffer), buffer_len);
    ifs.close();

    return buffer;
}

void WriteToFile(std::string argLocation, unsigned char *argContents, int argSize)
{
    std::ofstream myfile;
    myfile.open(argLocation);
    myfile.write((const char *)argContents, argSize);
    myfile.close();
}

int main()
{
    // Config
    static std::string szLocation   = "C:\\Users\\Admin\\Desktop\\putty.exe";
    static std::string szOutLoc     = "C:\\Users\\Admin\\Desktop\\putty2.exe";

    DWORD dwLen;
    unsigned char *szBytesIn = ReadFileAsBytes(szLocation, dwLen);

    std::cout << "Read In " << dwLen << " Bytes" << std::endl;

    // Write To File
    WriteToFile(szOutLoc, szBytesIn, dwLen);

    system("pause");
}

Slava · Accepted Answer · 2017-02-10 02:40:06Z

3

You open input file in binary mode, but in this code

std::ofstream myfile;
myfile.open(argLocation);

you open output file without binary mode. And there is no reason to call open separately:

std::ofstream myfile( argLocation, std::ios::out | std::ios::binary | std::ios::trunc);

answered Feb 10, 2017 at 2:40

Slava

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