CODEWITHSUNDEEP
c++arraysbit-manipulation
batista cori
batista cori

Reputation: 545

C++ Do operation on bits of a std::bitset

I want to AND 4 4-bits of a std::bitset<16> with each other. I mean:

std::bitset<16> arr("1100 1100 1100 1100");

I want to AND these 4-bits array.

std::bitset<4> a;

a= 1100 & 1100 & 1100 & 1100

I want to do this in the most efficient way. Not using for loops.

Thanks in Advance.

Upvotes: 1

Views: 339

Answers (3)

Danil Asotsky
Danil Asotsky

Reputation: 1241

One possible solution is:

unsigned long i = arr.to_ulong();
i = (i & (i >> 4) & (i >> 8) & (i >> 12)) & 0xf;
a = std::bitset<4>(i);

Upvotes: 1

111111
111111

Reputation: 16148

so long as you know how many bits the target and source are you can do this.

std::bitset<16> arr("1100110011001100");
std::bitset<4> v (
    ((arr    ) & 
     (arr>>4 ) & 
     (arr>>8 ) & 
     (arr>>12)).to_ulong() 
     &   0x0f
);

Upvotes: 2

Bo Persson
Bo Persson

Reputation: 92211

There is no shortcut with slicing bitsets. Just work your way through the bits

a[0] = arr[0] & arr[4] & arr[8] & arr[12];

etc.

It can't take the computer long to check 16 bits, however you do it!

Upvotes: 2

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