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__bit=[1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1] #Eingabe
g1=[16,5,3,1,0] #g1-g4 sind die Feedbackpolynome mit den entsprechenden Exponenten
g2=[16,0]
g3=[16,7,0]
g4=[16,14,13,11,0]

def LFSR(g):
  biterg=__bit[:]
  i=0 #Zyklenzaehler
  ausg=''
  run=True
  while run:
    k=biterg[g[0]]^biterg[g[1]] #rechnet XOR mit den ersten beiden Stellen
    for j in range(2,len(g)):
      k=k^biterg[g[j]] #verrechnet die weiteren Stellen XOR
    ausg=ausg+str(biterg[len(biterg)-1])
    biterg.insert(0,k) #fuegt neues Bit an erster Stelle ein  
    biterg.pop(len(biterg)-1) # nimmt letztes Bit weg
    i+=1
    if biterg==__bit:
      run=False
  return i,ausg

def main():
  print('Zyklenlaenge | Zyklus')
  print('a: ',LFSR(g1))
  print('b: ',LFSR(g2))
  print('c: ',LFSR(g3))
  print('d: ',LFSR(g4))

main()

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#include <stdlib.h>
#include <stdio.h>

int getDegree(unsigned int polynom){
	int result = 0;
	for(int i=0; i <32; i++){
		if(polynom&0x1){
			result=i;
		}
		polynom>>=1;
	}

	return result;
}

int getParity(unsigned int value){
	int result = 0;

	for(int i = 0; i<32;i++){
		result^=(value&0x1);
		value>>=1;
	}

	return result;
}

void printBinary(unsigned int value){
	char chars[33];
	chars[33]=0;

	printf("%X: ", value);

	for(int i = 32; i>=0; i--){
		chars[i] = 0x30 + value%2;
		value>>=1;
	}

	printf("%s\n", chars);
}

void lfsr(unsigned int polynom, unsigned int startWord){
	unsigned int degree = getDegree(polynom);
	unsigned int currentWord = 0;
	unsigned int wordMask = (0x1<<(degree))-1;
	unsigned int lsb = 0;

	printf("%d\n", degree);
	printf("%X\n", wordMask);
	printf("%X\n", startWord);

	polynom>>=1;

	startWord &= wordMask;

	currentWord = startWord;

	int ctr = 0;

	do{
		lsb = 0;

		lsb = getParity(currentWord&polynom);

		currentWord=((currentWord<<1) + lsb)&wordMask;

		printBinary(currentWord);

		ctr ++;

	} while(currentWord!=startWord);

	printf("ctr: %d\n", ctr);

}


int main(){
	
	lfsr(0x10001,0xFFFF);
	lfsr(0x1002B,0xFFFF);
	lfsr(0x10081,0xFFFF);
	lfsr(0x16801,0xFFFF);

	return EXIT_SUCCESS;
}