BigDigits C++ starter code

bign.hpp

#include <iostream>
#include <bigd.h>   // http://www.di-mgt.com.au/bigdigits.html
using namespace std;

namespace paiv
{
  typedef uint32_t u32;

  class Big
  {
  private:
    BIGD bn;
  public:
    explicit Big() : bn(bdNew()) {}
    Big(u32 x) : bn(bdNew()) { bdSetShort(bn, x); }
    ~Big() { if (bn) bdFree(&bn); bn = nullptr; }

    Big(const Big& x) : bn(bdNew()) { bdSetEqual(bn, x.bn); }
    Big(Big&& x) : bn(x.bn) { x.bn = nullptr; }

    explicit operator BIGD() const { return bn; }
    explicit operator u32() const { return bdToShort(bn); }

    Big& operator+= (const Big& y) { bdAdd_s((BIGD)*this, (BIGD)*this, (BIGD)y); return *this; }
    Big& operator-= (const Big& y) { bdSubtract_s((BIGD)*this, (BIGD)*this, (BIGD)y); return *this; }
    Big& operator*= (const Big& y) { bdMultiply_s((BIGD)*this, (BIGD)*this, (BIGD)y); return *this; }
  };

  inline bool operator== (const Big& x, const Big& y) { return bdCompare((BIGD)x, (BIGD)y) == 0; }
  inline Big operator+ (Big x, const Big& y) { return x += y; }
  inline Big operator- (Big x, const Big& y) { return x -= y; }
  inline Big operator* (Big x, const Big& y) { return x *= y; }
  inline Big pow (const Big& x, u32 n) { Big y; bdPower((BIGD)y, (BIGD)x, n); return y; }

  ostream& operator<< (ostream& so, const Big& x)
  {
    auto conv = (so.flags() & ios::hex) ? bdConvToHex : bdConvToDecimal;
    size_t size = conv((BIGD)x, nullptr, 0) + 1;
    string s(size, '\0');
    conv((BIGD)x, &s[0], size);
    return so << s;
  }

}