Convert integer to bits

I have byte to binary string function,

std::string byte_to_binary(unsigned char byte) { int x = 128; std::ostringstream oss; oss << ((byte & 255) != 0); for (int i = 0; i < 7; i++, x/=2) oss << ((byte & x) != 0); return oss.str(); } 

How can i write an int to bits in same way? I don't want extra 0's at the beginning of binary string so that is why i can't figure out how to create a variable length each time. Also, i'm not using std::bitset.

4 Answers

I'll just post this as an answer. It is shorter, safer and, what's most important, it is done.

#include <string> #include <bitset> #include <type_traits> // SFINAE for safety. Sue me for putting it in a macro for brevity on the function #define IS_INTEGRAL(T) typename std::enable_if< std::is_integral<T>::value >::type* = 0 template<class T> std::string integral_to_binary_string(T byte, IS_INTEGRAL(T)) { std::bitset<sizeof(T) * CHAR_BIT> bs(byte); return bs.to_string(); } int main(){ unsigned char byte = 0x03; // 0000 0011 std::cout << integral_to_binary_string(byte); std::cin.get(); } 

Output:

00000011

Changed function name, though I'm not happy with that one... anyone got a nice idea?

Something like this should work (though I hacked it up quickly and haven't tested):

#include <string> #include <climits> template<typename T> std::string to_binary(T val) { std::size_t sz = sizeof(val)*CHAR_BIT; std::string ret(sz, ' '); while( sz-- ) { ret[sz] = '0'+(val&1); val >>= 1; } return ret; } 

You can do it using std:bitset and convert any number into bit string of any size, for example 64

#include <string> #include <iostream> #include <bitset> using namespace std; int main() { std::bitset<64> b(836); //convent number into bit array std::cout << "836 in binary is " << b << std::endl; //make it string string mystring = b.to_string<char,char_traits<char>,allocator<char> >(); std::cout << "binary as string " << mystring << endl; } 

Since you mentioned your wish for C style in the comments, you might consider using itoa (or _itoa) if you are not worried about ANSI-C standard. Many compilers support it in stdlib.h. It also strips the leading 0's:

unsigned char yourGoldenNumber = 42; char binCode[64]; itoa(yourGoldenNumber,binCode,2); // third parameter is the radix puts(binCode); // 101010