comparing two binary files

//http://collabedit.com/6qv2p

#include <fstream>
#include <cassert>

//Reference: https://en.cppreference.com/w/cpp/io/ios_base/iostate

class StreamCompare{
private:
    void assert_exceptions_are_turned_on(std::istream& s){
        assert(s.exceptions() & std::ios_base::badbit);
        assert(s.exceptions() & std::ios_base::failbit);
    }

public:
    bool compare_two_streams(std::istream& stream1, std::istream& stream2){
        assert_exceptions_are_turned_on(stream1);
        assert_exceptions_are_turned_on(stream2);

        auto stream_size1 = stream1.tellg();
        auto stream_size2 = stream2.tellg();

        if(stream_size1 != stream_size2){
            return false;
        }

        constexpr int bufferSize = 4*1024*1024;

        char buffer1[bufferSize];
        char buffer2[bufferSize];

        stream1.seekg(0, std::ios_base::beg);
        stream2.seekg(0, std::ios_base::beg);

        int data_read_so_far_on_both_streams = 0;

        while((!stream1.eof() && !stream2.eod()) && (data_read_so_far_on_both_streams < stream_size1)){
            int data_to_read_on_both_streams = std::min({stream_size1 - data_read_so_far_on_both_streams, bufferSize});

            stream1.read(buffer1, data_to_read_on_both_streams);
            stream2.read(buffer2, data_to_read_on_both_streams);

            int data_actually_read_on_stream1 = stream1.gcount();
            int data_actually_read_on_stream2 = stream1.gcount();

            bool is_equal = std::equals(std::begin(buffer1), std::begin(buffer1) + data_actually_read_on_stream1,
                                        std::begin(buffer2), std::begin(buffer2) + data_actually_read_on_stream2);
            if(!is_equal){
                return false;
            }
        }
        return true;
    }
};