crc1.cpp

循环冗余校验

#include<stdio.h> 
int main() 
{ 
void crc(unsigned long M,unsigned long G); 
unsigned long M,G; 
printf("Please put 2 sequences:\n"); 
scanf("%lu%lu",&M,&G); 
printf("\n\nThe data is =%lu,the generator polynomial is =%lu\n\n\n",M,G); 
crc(M,G); 
return 0; 
} 

void crc(unsigned long M,unsigned long G) 
{ 
/* M是数据，G是生成多项式，皆为无符长整型*/ 
void trans2(unsigned long s,unsigned *t,int *n); 
void result_printf(unsigned s,int n);  
unsigned mD,gD,g;                       /*将输入的序列(10进制形式)用2进制mD,gD存储*/ 
int mN=0,gN=0; 
int MASK=1,i; 
trans2(M,&mD,&mN); 
trans2(G,&gD,&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2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该向右移多少位*/ 
  gD>>=i; 
  if(g>gD) break; 
} 
printf("The check is:"); 
result_printf(mD,gN-1); 
} 

void trans2(unsigned long s,unsigned *t,int *n)    
/*10进制格式转换成2进制存储， 
  s为待转换数，t为转换结果，n为转换后的2进制位数*/ 
{                    
    if(s<10) *t=s;  
else { 
  trans2(s/10,t,n); 
  *t=(*t)*2+s%10; 
  } 
(*n)++; 
} 
void result_printf(unsigned s,int n) 
{ 
/*输出结果，即余数*/ 
 if(n!=1) result_printf(s/2,n-1); 
 printf("%d",s%2); 
}