Re: write binary representation to output

From:

Juha Nieminen <nospam@thanks.invalid>

Newsgroups:

comp.lang.c++

Date:

Sat, 19 Apr 2008 11:19:21 +0300

Message-ID:

<4809aafe$0$8175$4f793bc4@news.tdc.fi>

wongjoekmeu@yahoo.com wrote:

I was wondering how in C++ the code would look like if I want to write
the binary notation of a unsigned char to standard output or any other
basic data type, like int, unsigned int, float and so forth.

#include <iostream>
#include <climits>

template<typename Type>
void printBinaryRepresentation(const Type& value)
{
    // Resolve if this is a big-endian or a little-endian system:
    int dummy = 1;
    bool littleEndian = (*reinterpret_cast<char*>(&dummy) == 1);

    // The trick is to create a char pointer to the value:
    const unsigned char* bytePtr =
        reinterpret_cast<const unsigned char*>(&value);

    // Loop over the bytes in the value:
    for(unsigned i = 0; i < sizeof(Type); ++i)
    {
        unsigned char byte;
        if(littleEndian) // we have to traverse the value backwards:
            byte = bytePtr[sizeof(Type) - i - 1];
        else // we have to traverse it forwards:
            byte = bytePtr[i];

        // Print the bits in the byte:
        for(int bitIndex = CHAR_BIT-1; bitIndex >= 0; --bitIndex)
        {
            std::cout << ((byte >> bitIndex) & 1);
        }
    }

    std::cout << std::endl;
}