mycrc.cpp

通过输入两个序列生成crc余数

#include<stdio.h>


int main()
{
void crc(unsigned long M,unsigned long G);
unsigned long M,G,C;
printf("Please input two xulie:\n");
scanf("%lu%lu",&M,&G);
printf("M：%lu\n",M);
printf("G：%lu\n",G);
crc(M,G);

return 0;
}


void transfer(unsigned long s,unsigned *t,int *n)
{    *t=0;
     *n=0;
    if(s<10) *t=s;
    else {
     transfer(s/10,t,n);
     *t=(*t)*2+s%10;
         }
     (*n)++;
}


/*输出余数函数*/
int output(unsigned s,int n)
{
 int a;
 if(n!=1) output(s/2,n-1);
 printf("%d",s%2);
 a=s%2;
 return a;
}

/*CRC过程*/
void crc(unsigned long M,unsigned long G)
{
    void transfer(unsigned long s,unsigned *t,int *n);
    int output(unsigned s,int n);
    unsigned mD,gD,g;

    int a2;

    int mN=0,gN=0;
  	int MASK=1,i,h;
	transfer(M,&mD,&mN);
	transfer(G,&gD,&gN);
	
	h=mN-gN;
    g=gD;
	mD<<=gN-1;
	gD<<=mN-1;
	MASK<<=gN+mN-2;
  for(mD=mD^gD;mD!=0;mD=mD^gD)                    /*for语句,模二除法的实现*/
  {
  	for(i=0;(mD&MASK)!=MASK;MASK>>=1) i++;          /*MASK的作用:确认生成多项式G向右移动多少位*/
    gD>>=i;
  if(g>gD) break;
  }
 printf("yushu:\n");
	output(mD,gN-1);
	


 unsigned long C;
 unsigned cD,gD2,g2;
 int cN=0,gN2=0;	
 int MASK2=1,j,h2;

 transfer(G,&gD2,&gN2);
 printf("\n\n\n");
 printf("Please input crc:\n");
 scanf("%lu",&C);
  transfer(C,&cD,&cN);
  transfer(G,&gD,&gN);
    h2=cN-gN2;
	g2=gD2;
	cD<<=gN2-1;
	gD2<<=cN-1;
	MASK2<<=gN2+cN-2;
  for(cD=cD^gD2;cD!=0;cD=cD^gD2)
  {
  	for(j=0;(cD&MASK2)!=MASK2;MASK2>>=1) j++;
    gD2>>=j;
  if(g>gD2) break;
  }	
  printf("yushu:");
	a2=output(cD,gN2-1);
	if(a2==0)
      printf("\nOK!");
	else
      printf("\nWrong!");	
	printf("\n");
	
}