Binary open and copy image file c++

Question

I want to copy one image file to another new file. This is my method to do this:

    std::ofstream myOutpue;
    std::ifstream mySource;
    //int i = 0;
    mySource.open(ofn.lpstrFile, std::ios::binary);
    myOutpue.open("im4.jpg", std::ios::binary);
    char buffer;
    char bufferToSave[100];
    if (mySource.is_open())
    {
        //client->sendFilePacket(FileStates::START_SAVE, buffer, false,i);
        i++;
        while (!mySource.eof())
        {
            mySource >> std::noskipws >> buffer;
            myOutpue << buffer;
            //client->sendFilePacket(FileStates::CONTINUE_SAVE, buffer, false,i);
            i++;
        }
    }
    i++;
    //client->sendFilePacket(FileStates::END_SAVE, buffer, true,i);
    mySource.close();
    //myOutpue.close();

This method work correctly, but my problem is that i want to copy char/bit's and send it to another client. When i doing this by each char , that not work correctly so i want to make a bigger buffor(for example char t[512]) or something like that and copy them to new file.

I try to doing this like that:

    std::ofstream myOutpue;
    std::ifstream mySource;
    mySource.open(ofn.lpstrFile, std::ios::binary);
    myOutpue.open("im4.jpg", std::ios::binary);
    char buffer;
    char bufferToSave[100];
    if (mySource.is_open())
    {
        //client->sendFilePacket(FileStates::START_SAVE, buffer, false,i);
        i++;
        while (!mySource.eof())
        {
            if (i == 100)
            {
                for (int i = 0; i < 100; i++)myOutpue << bufferToSave[i];
                i = 0;
            }
            mySource >> std::noskipws >> buffer;
            bufferToSave[i] = buffer;
            //myOutpue << buffer;
            //client->sendFilePacket(FileStates::CONTINUE_SAVE, buffer, false,i);
            i++;
        }
    }
    i++;
    //client->sendFilePacket(FileStates::END_SAVE, buffer, true,i);
    mySource.close();
    myOutpue.close();

But i get image that i can't open.

So my question is how to read file to get more bits from it and that create me the same image as original.

Answer 1

You have an error in your original file copy algorithm in that you should never loop using eof() as the end flag.

See: Why is iostream::eof inside a loop condition considered wrong?

Copying files can be a simple as this:

    std::ofstream("output.jpg", std::ios::binary) << std::ifstream("input.jpg", std::ios::binary).rdbuf();

It uses a special overload of the output operator when passing an std::istream buffer (using rdbuf()). It copies the whole stream.

When reading a whole buffer you should use std::istream::read:

    std::ifstream ifs("input.jpg", std::ios::binary)

    char buffer[1025]; // create a buffer

    // keep going as long as the reading succeeds
    while(ifs.read(buffer, sizeof(buffer)))
    {
        // ifs.gcount() is the number of chars read successfully
        client->sendFilePacket(buffer, ifs.gcount()); // send all bytes
    }