C++ - 将任何文件的字节读入无符号字符数组

Question

I have an assignment where I have to implement the Rijndael Algorithm for AES-128 Encryption. I have the algorithm operational, but I do not have proper file input/output.

The assignment requires us to use parameters passed in from the command line. In this case, the parameter will be the file path to the particular file the user wishes to encrypt.

My problem is, I am lost as to how to read in the bytes of a file and store these bytes inside an array for later encryption.

I have tried using ifstream and ofstream to open, read, write, and close the files and it works fine for plaintext files. However, I need the application to take ANY file as input.

When I tried my method of using fstream with a pdf as input, it would crash my program. So, I now need to learn how to take the bytes of a file, store them inside an unsigned char array for Encryption, and then store them inside another file. This process of encryption and storage of ciphertext needs to occur in 16 byte intervals.

The below implementation is my first attempt to read files in binary mode and then write whatever was read in another file also in binary mode. The output is readable in a hex reader.

int main(int argc, char* argv[])
{
    if (argc < 2)
    {
        cerr << "Use: " << argv[0] << " SOURCE_FILEPATH" << endl << "Ex. \"C\\Users\\Anthony\\Desktop\\test.txt\"\n";
        return 1;
    }

    // Store the Command Line Parameter inside a string
    // In this case, a filepath.
    string src_fp = argv[1];
    string dst_fp = src_fp.substr(0, src_fp.find('.', 0)) + ".enc";

    // Open the filepaths in binary mode
    ifstream srcF(src_fp, ios::in | ios::binary);
    ofstream dstF(dst_fp, ios::out | ios::binary);

    // Buffer to handle the input and output.
    unsigned char fBuffer[16];

    srcF.seekg(0, ios::beg);
    while (!srcF.eof())
    {
        srcF >> fBuffer;

        dstF << fBuffer << endl;
    }

    dstF.close();
    srcF.close();
}

The code implementation does not work as intended.

Any direction on how to solve my dilemma would be greatly appreciated.

Answer 1

Like you, I really struggled to find a way to read a binary file into a byte array in C++ that would output the same hex values I see in a hex editor. After much trial and error, this seems to be the fastest way to do so without extra casts.

It would go faster without the counter, but then sometimes you end up with wide chars. To truly get one byte at a time I haven't found a better way.

By default it loads the entire file into memory, but only prints the first 1000 bytes.

string Filename = "BinaryFile.bin";
FILE* pFile;
pFile = fopen(Filename.c_str(), "rb");
fseek(pFile, 0L, SEEK_END);
size_t size = ftell(pFile);
fseek(pFile, 0L, SEEK_SET);
uint8_t* ByteArray;
ByteArray = new uint8_t[size];
if (pFile != NULL)
{
    int counter = 0;
    do {
        ByteArray[counter] = fgetc(pFile);
        counter++;
    } while (counter <= size);
    fclose(pFile);
}
for (size_t i = 0; i < 800; i++) {
    printf("%02X ", ByteArray[i]);
}