Bit field vs Bitset

Question

I want to store bits in an array (like structure). So I can follow either of the following two approaches

Approach number 1 (AN 1)

struct BIT
{
   int da         


        

Answer 1

To quote cplusplus.com's page on bitset, "The class is very similar to a regular array, but optimizing for space allocation". If your ints are 4 bytes, a bitset uses 32 times less space.

Even doing bool bits[100], as sbi suggested, is still worse than bitset, because most implementations have >= 1-byte bools.

If, for reasons of intellectual curiosity only, you wanted to implement your own bitset, you could do so using bit masks:

typedef struct {
  unsigned char bytes[100];
} MyBitset;

bool getBit(MyBitset *bitset, int index)
{
  int whichByte = index / 8; 
  return bitset->bytes[whichByte] && (1 << (index = % 8));
}

bool setBit(MyBitset *bitset, int index, bool newVal)
{
  int whichByte = index / 8;

  if (newVal)
  {
    bitset->bytes[whichByte] |= (1 << (index = % 8));
  }
  else
  {
    bitset->bytes[whichByte] &= ~(1 << (index = % 8));
  }
}

(Sorry for using a struct instead of a class by the way. I'm thinking in straight C because I'm in the middle of a low-level assignment for school. Obviously two huge benefits of using a class are operator overloading and the ability to have a variable-sized array.)