How to visualize bytes with C/C++

Question

I\'m working my way through some C++ training. So far so good, but I need some help reinforcing some of the concepts I am learning. My question is how do I go about visualiz

Answer 1

A little bit by bit console program i whipped up, hope it helps somebody

#include <iostream>
#include <inttypes.h>
#include <vector>
using namespace std;
typedef  vector<uint8_t> ByteVector;
///////////////////////////////////////////////////////////////
uint8_t Flags[8] = { 0x01,0x02,0x04,0x08,0x10,0x20,0x40,0x80};
void print_bytes(ByteVector Bv){
    for (unsigned i = 0; i < Bv.size(); i++){
        printf("Byte %d [ ",i);
        for (int j  = 0;j < 8;++j){
            Bv[i] & Flags[j] ? printf("1") : printf("0");
        }
        printf("]\n");
    }
}
int main(){
    ByteVector Bv;
    for (int i = 0; i < 4; ++i) { Bv.push_back(i); }
    print_bytes(Bv);
}

Answer 2

If you are using gcc and X, you can use the DDD debugger to draw pretty pictures of your data structures for you.

Answer 3

You can use a function such as this, to print the bytes:

static void print_bytes(const void *object, size_t size)
{
#ifdef __cplusplus
  const unsigned char * const bytes = static_cast<const unsigned char *>(object);
#else // __cplusplus
  const unsigned char * const bytes = object;
#endif // __cplusplus

  size_t i;

  printf("[ ");
  for(i = 0; i < size; i++)
  {
    printf("%02x ", bytes[i]);
  }
  printf("]\n");
}

Usage would look like this, for instance:

int x = 37;
float y = 3.14;

print_bytes(&x, sizeof x);
print_bytes(&y, sizeof y);

This shows the bytes just as raw numerical values, in hexadecimal which is commonly used for "memory dumps" like these.

On a random (might even be virtual, for all I know) Linux machine running a "Intel(R) Xeon(R)" CPU, this prints:

[ 25 00 00 00 ]
[ c3 f5 48 40 ]

This handily also demonstrates that the Intel family of CPU:s really are little endian.

Answer 4

Or if you have the boost lib and want to use lambda evaluations you can do it this way ...

template<class T>
void bytePattern( const T& object )
{
    typedef unsigned char byte_type;
    typedef const byte_type* iterator;

    std::cout << "Object type:" << typeid( T ).name() << std::hex;
    std::for_each( 
        reinterpret_cast<iterator>(&object), 
        reinterpret_cast<iterator>(&object) + sizeof(T), 
        std::cout << constant(' ') << ll_static_cast<int>(_1 )&&0xFF );   
    std::cout << "\n";
}

Answer 5

Just for completeness, a C++ example:

#include <iostream>

template <typename T>
void print_bytes(const T& input, std::ostream& os = std::cout)
{
  const unsigned char* p = reinterpret_cast<const unsigned char*>(&input);
  os << std::hex << std::showbase;
  os << "[";
  for (unsigned int i=0; i<sizeof(T); ++i)
    os << static_cast<int>(*(p++)) << " ";
  os << "]" << std::endl;;
}

int main()
{
  int i = 12345678;
  print_bytes(i);
  float x = 3.14f;
  print_bytes(x);
}

Answer 6

try this:

MyClass* myObj = new MyClass();
int size=sizeof(*myObj);
int i;
char* ptr = obj; // closest approximation to byte
for( i=0; i<size; i++ )
    std::cout << *ptr << endl;

Cheers,

jrh.