C++: Store read binary file into buffer

I just want to mention that there is a standard way to read from a binary file into a buffer.

Using <cstdio>:

char buffer[BUFFERSIZE];

FILE * filp = fopen("filename.bin", "rb"); 
int bytes_read = fread(buffer, sizeof(char), BUFFERSIZE, filp);

Using <fstream>:

std::ifstream fin("filename.bin", ios::in | ios::binary );
fin.read(buffer, BUFFERSIZE);

What you do with the buffer afterwards is all up to you of course.

Edit: Full example using <cstdio>

#include <cstdio>

const int BUFFERSIZE = 4096;    

int main() {
    const char * fname = "filename.bin";
    FILE* filp = fopen(fname, "rb" );
    if (!filp) { printf("Error: could not open file %s\n", fname); return -1; }

    char * buffer = new char[BUFFERSIZE];
    while ( (int bytes = fread(buffer, sizeof(char), BUFFERSIZE, filp)) > 0 ) {
        // Do something with the bytes, first elements of buffer.
        // For example, reversing the data and forget about it afterwards!
        for (char *beg = buffer, *end=buffer + bytes; beg < end; beg++, end-- ) {
           swap(*beg, *end);
        }
    }

    // Done and close.
    fclose(filp);

    return 0;
}

The problem is definitievely the writing of your buffer, because you read a byte at a time.

If you know the length of the data in your buffer, you could force cout to go on:

char *bf = "Hello\0 world"; 
cout << bf << endl;
cout << string(bf, 12) << endl;

This should give the following output:

Hello
Hello  world

However this is a workaround, as cout is foreseent to output printable data. Be aware that the output of non printable chars such as '\0' is system dependent.

Alternative solutions:

But if you manipulate binary data, you should define ad-hoc data structures and printing. Here some hints, with a quick draft for the general principles:

struct Mybuff {   // special strtucture to manage buffers of binary data
    static const int maxsz = 512; 
    int size;
    char buffer[maxsz]; 
    void set(char *src, int sz)  // binary copy of data of a given length
    { size = sz; memcpy(buffer, src, max(sz, maxsz)); }
} ; 

Then you could overload the output operator function:

ostream& operator<< (ostream& os, Mybuff &b)
{
    for (int i = 0; i < b.size; i++) 
        os.put(isprint(b.buffer[i]) ? b.buffer[i]:'*');  // non printables replaced with *
    return os;
}

ANd you could use it like this:

char *bf = "Hello\0 world"; 
Mybuff my; 
my.set(bf, 13);   // physical copy of memory
cout << my << endl;   // special output 

static std::vector<unsigned char> read_binary_file (const std::string filename)
{
    // binary mode is only for switching off newline translation
    std::ifstream file(filename, std::ios::binary);
    file.unsetf(std::ios::skipws);

    std::streampos file_size;
    file.seekg(0, std::ios::end);
    file_size = file.tellg();
    file.seekg(0, std::ios::beg);

    std::vector<unsigned char> vec(file_size);
    vec.insert(vec.begin(),
               std::istream_iterator<unsigned char>(file),
               std::istream_iterator<unsigned char>());
    return (vec);
}

and then

auto vec = read_binary_file(filename);
auto src = (char*) new char[vec.size()];
std::copy(vec.begin(), vec.end(), src);