C ofstream Binary Mode - Written file still looks like plain text-CodePudding

I have an assignment that wants plain text data to be read in from a file, and then outputted to a separate binary file. With that being said, I expect to see that the contents of the binary file not to be intelligible for human reading. However, when I open the binary file the contents are still appearing as plain text. I am setting the mode like this _file.open(OUTFILE, std::ios::binary). I can't seem to figure out what I'm missing. I've followed other examples with different methods of implementation, but there's obviously something I'm missing.

For the purpose of posting, I created a slimmed down test case to demonstrate what I'm attempting.

Thanks in advance, help is greatly appreciated!

Input File: test.txt

Hello World

main.cpp

#include <iostream>
#include <fstream>

using namespace std;

#define INFILE "test.txt"
#define OUTFILE "binary-output.dat"


int main(int argc, char* argv[]) {

    char* text = nullptr;
    int nbytes = 0;
    // open text file
    fstream input(INFILE, std::ios::in);
    if (!input) {
        throw "\n***Failed to open file "   string(INFILE)   " ***\n";
    }

    // copy from file into memory
    input.seekg(0, std::ios::end);
    nbytes = (int)input.tellg()   1;

    text = new char[nbytes];

    input.seekg(ios::beg);
    int i = 0;
    input >> noskipws;
    while (input.good()) {
        input >> text[i  ];
    }
    text[nbytes - 1] = '\0';
    cout << "\n" << nbytes - 1 << " bytes copied from file " << INFILE << " into memory (null byte added)\n";

    if (!text) {
        throw "\n***No data stored***\n";
    } else {
        // open binary file for writing
        ofstream _file;
        _file.open(OUTFILE, std::ios::binary);

        if (!_file.is_open()) {
            throw "\n***Failed to open file***\n";
        } else {
            // write data into the binary file and close the file
            for (size_t i = 0U; i <= strlen(text);   i) {
                _file << text[i];
            }

            _file.close();
        }
    }
}

CodePudding user response：

As stated here, std::ios::binary isn't actually going to write binary for you. Basically, it's the same as std::ios::out except things like \n aren't converted to line breaks.

You can convert text to binary by using <bitset>, like this:

#include <iostream>
#include <vector>
#include <bitset>

int main() {
    std::string str = "String in plain text";
    std::vector<std::bitset<8>> binary; // A vector of binaries

    for (unsigned long i = 0; i < str.length();   i) {
        std::bitset<8> bs4(str[i]);
        binary.push_back(bs4);
    }

    return 0;
}

And then write to your file.

CodePudding user response：

In simplest terms, the flag std::ios::binary means:

Do not make any adjustments to my output to aid in readability or conformance to operating system standards. Write exactly what I send.

In your case, you are writing readable text and the file contains exactly what you sent.

You could also write bytes that are unintelligible when viewed as text. In that case, your file would be unintelligible when viewed as text.