A variable length bitset in C++ [duplicate] - c++

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Define bitset size at initialization?
(7 answers)
Closed 5 years ago.
I have a working 4 bit linear feedback shift register, using 3 bitsets of length 4: inpSeq, operSeq and bit. I want to make the program accept a variable length bit sequence, so those previous bitsets should be of variable length somehow. The user may enter a sequence ofr inpSeq and the program sets the three bitsets to be of the same length as that sequence provided by the user. Any ideas for how to achieve this? Sample code if I may ask!
Here is the code:
#include <iostream> //Standard library.
#include <bitset> //Library for 10 handling.
#include <vector> //Variable size array.
#include <algorithm> //We use sorting from it.
using namespace std;
int main()
{
int y = 0;
int turnCount = 0;
int count1 = 0, count0 = 0;
bitset <4> inpSeq;
int polyLoc;
bitset <4> operSeq;
bitset <4> bit;
vector <int> xorArray;
vector <int> keyReg;
cout << "Enter a 4-bit sequence: \n";
cin >> inpSeq;
cout << "Enter polynomial:";
cin >> polyLoc;
while(polyLoc>0)
{
xorArray.push_back(polyLoc%10);
polyLoc/=10;
}
cout << "xorArray is: ";
for ( unsigned int i = 0; i < xorArray.size(); i++)
{
cout << xorArray[i] << " ";
}
sort(xorArray.rbegin(), xorArray.rend());
cout << "\n";
operSeq = inpSeq;
keyReg.push_back(inpSeq[0]);
int x = xorArray[0];
cout << "x is: " << x << "\n";
for ( unsigned int i = 0; i < xorArray.size(); i++)
{
cout << xorArray[i] << "\n";
}
cout << "bit 3 of initial " << bit[3] << "\n";
do {
for (unsigned int r = 1; r < xorArray.size(); r++)
{
bit[3] = operSeq[x];
cout << "bit 3 from prev: " << bit[3] << "\n";
y = xorArray[r];
cout << "opseq[y] is: " << operSeq[y] << "\n";
bit[3] = bit[3] ^ operSeq[y];
cout << "bit[3] after xor: " << bit[3] << "\n";
}
operSeq >>= 1;
cout <<"operSeq after shift: " << operSeq << "\n";
operSeq[3] = bit[3];
cout <<"opserSeq bit 4 after = bit[3]: " << operSeq[3] << "\n";
cout <<"new operSeq: " << operSeq << "\n";
keyReg.push_back(operSeq[0]);
turnCount ++;
cout << "--\n";
}
while ((operSeq != inpSeq) && (turnCount < 20));
cout << "Generated key is: ";
for (unsigned int k = 0; k < keyReg.size(); k++)
{
cout << keyReg[k];
}
cout << "\n";
cout << "Bit 1 positions: ";
for ( unsigned int g = 0; g < xorArray.size(); g++)
{
cout << xorArray[g];
}
cout << "\n";
cout << "Key length is: " << keyReg.size();
cout << "\n";
for ( unsigned int i = 0; i < keyReg.size(); i++)
{
if (keyReg[i]==1)
{
count1++;
}
else {
count0++;
}
}
cout << "Number of 0's: " << count0 << "\n";
cout << "Number of 1's: " << count1 << "\n";
if ( keyReg.size()%2 ==0)
{
cout << "key length is even. \n";
if (count1==count0)
{
cout << "Key is perfect! \n";
}
else {
cout << "Key is not perfect! \n";
}
}
else
{
cout << "key length is odd. \n";
if ((count1==count0+1) || (count0==count1+1))
{
cout << "Key is perfect! \n";
}
else {
cout << "Key is not perfect! \n";
}
}
cin.get();
}

Answer 1

std::vector has an optimization for std::vector<bool>, and the size of a vector can be set at runtime.