Bitset is divided into characters

Question

I have a fairly large set of bits:

bitset<128*8> bs; 

I would like to have access to groups of 8 bits. What because of this so far:

• bs.to_string ()
• splits into a row vector of size 8
• create a new bittet from these lines and call to_ulong ()

Is there a better solution? Performance is critical as I call this method several times in my program.

Answer 1

std::bitset has a >> operator.

If you just want to access the value and read it, you can use the code below. It reads Nth 8 bits as uint8_t :

 bitset<128*8> mask(0xFF); uint8_t x = ((bs >> N * 8) & mask).to_ulong(); 

Answer 2

You can do something similar to avoid creating lines and some copying:

 for (uint32_t i = 0; i < bs.size(); i+=8) { uint32_t uval = 0; for (uint32_t j = 0; j < 8; j++) { uval = (uval << 1) + bs[i + 7 - j]; } std::cout << uval << std::endl; } 

but you may have to work with indexes depending on your entity