Counting transitions in a bit string

transitions.cpp

 
template <class T> void bitstr(const T& out) noexcept;
template <class T> int  popcnt(const T& val) noexcept;
 
int main()
{
    // Uniform descriptors
    // 0000 0000  (0 Transitions : Uniform)    0x0
    // 1110 0011  (2 Transitions : Uniform)    0xE3
    // 0101 0000  (4 Transitions : NonUniform) 0x50
    // 0000 1010  (4 Transitions : NonUniform) 0xA
    // 0000 1001  (3 Transitions : NonUniform) 0x9
 
    int a = 0xE3;
    int b = a >> 1;
    int c = a ^ b;
    int count = popcnt(c);
 
    bitstr(a);
    bitstr(b);
    bitstr(c);
 
    std::cout << "Transition : " <<count;
 
    return 0;
}
 
 
template <class T>
int popcnt(const T& val) noexcept
{
    int bitcount;
    __asm__ ("popcnt %1, %1" : "=r" (bitcount) : "0" (val));
    return bitcount;
}
 
template <class T>
void bitstr(const T& out) noexcept
{
    std::bitset<CHAR_BIT * sizeof(T)> bs(out);
    auto val =  static_cast<int>(out);
    std::cout << "0x"
              << std::setw(8) << std::hex << val << " : "
              << std::setw(8) << std::dec << val<< " :: " << bs << std::endl;
}