in bitset, can i use “to_ulong” for a specific range of bits?

问题

hi im working on something that demands me to get access to specific/range of bits. i decided to use bitset because it is easy to get access to specific bits but can i extract a whole range of bits?

回答1:

Method A:

return (the_bitset >> start_bit).to_ulong();

Method B (faster than method A by 100 times on my machine):

unsigned long mask = 1;
unsigned long result = 0;
for (size_t i = start_bit; i < end_bit; ++ i) {
    if (the_bitset.test(i))
       result |= mask;
    mask <<= 1;
}
return result;

来源：https://stackoverflow.com/questions/2177186/in-bitset-can-i-use-to-ulong-for-a-specific-range-of-bits