#define SIZE_OF_ARRAY(x)        ((sizeof(x))/(sizeof(x[0])))

typedef union
{
  uint32_t bit32;
  double_t  varDbl;
}entropy_var_t;

static double_t get_entropy(uint8_t const * p_src, size_t const buffer_size)
{
  double_t ret_val = 0;
  entropy_var_t bins[UINT8_MAX];

  memset(bins, 0, sizeof(bins));

  /* Count occurance of each byte */
  for(uint32_t itr = 0; itr < buffer_size; itr++)
  {
    bins[p_src[itr]].bit32+=1;
  }

  for(uint32_t itr = 0; itr < SIZE_OF_ARRAY(bins); itr++)
  {
    bins[itr].varDbl = (double_t)bins[itr].bit32/(double_t)buffer_size;

    if(bins[itr].varDbl > 0.0)
    {
      double_t log2p_i = log2(bins[itr].varDbl);
      ret_val = ret_val + (bins[itr].varDbl * log2p_i);
    }
  }

  return -ret_val;
}

void test(void)
{

  uint8_t test_string[] =
  {
    0x0A, 0x0A, 0x0A, 0x0A, 0x0A,
    0x0B, 0x0B,
    0x0C,
    0x0D,
    0x0E
  };

  double_t test_entropy = get_entropy(&test_string[0], SIZE_OF_ARRAY(test_string));

  return;
 }