/* zero_crc.c - Don Yang (uguu.org)

   Append C comment to program such that CRC is zero.

   2015-10-02
*/
#include<assert.h>
#include<stdio.h>

static int table[256];
static const char tail[] = "*/\n";
static char pad[6];

int main()
{
   int i, j;
   unsigned c, tail0, c0;

   /* Build CRC table */
   for(i = 0; i < 256; i++)
   {
      c = i;
      for(j = 0; j < 8; j++)
      {
         if( (c & 1) != 0 )
            c = (c >> 1) ^ 0xedb88320;
         else
            c >>= 1;
      }
      table[i] = c;
   }

   /* Compute tail value needed to be matched */
   for(tail0 = 0; ++tail0 != 0;)
   {
      c = tail0;
      for(i = 0; tail[i] != '\0'; i++)
      {
         j = tail[i];
         c = (c >> 8) ^ table[(c ^ j) & 0xff];
      }
      if( c == ~0 )
         break;
   }
   assert(tail0 == 0xa32409ab);

   /* Process input */
   c = ~0;
   while( (i = getchar()) != EOF )
   {
      putchar(i);
      c = (c >> 8) ^ table[(c ^ i) & 0xff];
   }

   /* Compute fudge bytes needed */
   c = (c >> 8) ^ table[(c ^ '/') & 0xff];
   c = (c >> 8) ^ table[(c ^ '*') & 0xff];
   for(i = 0; i < 6; i++)
      pad[i] = ';';
   do
   {
      c0 = c;
      for(i = 0; i < 6; i++)
         c0 = (c0 >> 8) ^ table[(c0 ^ pad[i]) & 0xff];
      if( c0 == tail0 )
         break;

      for(i = 0; i < 6; i++)
      {
         pad[i]++;
         if( pad[i] > 'z' )
            pad[i] = ';';
         else
            break;
      }
   } while( i < 6 );
   printf("/*%c%c%c%c%c%c*/\n",
          pad[0], pad[1], pad[2], pad[3], pad[4], pad[5]);
   return 0;
}
/*qYdUj<*/