BitFlip.cpp

#include <windows.h>
#include <cstdint>

void DisplayError(DWORD ErrCode) {
    const char* msg;
    FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM, 0, ErrCode, 0, (char*)&msg, 0, 0);
    MessageBoxA(0, msg, "Problem", MB_OK);
    exit(0);
}

__forceinline bool BitFlipFile(wchar_t* FilePath) {
    HANDLE hFile = CreateFileA((char*)FilePath, GENERIC_ALL, 0, nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);

    if (hFile == INVALID_HANDLE_VALUE)
        DisplayError(GetLastError());

    uint64_t FileSize = GetFileSize(hFile, nullptr);

    if (!FileSize)
        DisplayError(GetLastError());

    void* File = malloc(FileSize);

    if (File == nullptr)
        DisplayError(GetLastError());

    if (!ReadFile(hFile, File, FileSize, nullptr, nullptr))
        DisplayError(GetLastError());

    for (uint64_t i = 0; i < FileSize; i++) {
        byte* FileByte = (byte*)((uint64_t)File + i);
        *FileByte = ~*FileByte;
    }

    SetFilePointer(hFile, 0, 0, FILE_BEGIN);

    if (!WriteFile(hFile, File, FileSize, nullptr, nullptr))
        DisplayError(GetLastError());

    free(File);

    if (!CloseHandle(hFile))
        DisplayError(GetLastError());

    return true;
}

int main(int argc, wchar_t* argv[], wchar_t* envp[]) {
    BitFlipFile(argv[1]);
    return 0;
}