** of four bytes.
*/
static unsigned int checksum(const char *zIn, size_t N){
  static const int byteOrderTest = 1;
  const unsigned char *z = (const unsigned char *)zIn;
  const unsigned char *zEnd = (const unsigned char*)&zIn[N&~3];
  unsigned sum = 0;
  assert( (z - (const unsigned char*)0)%4==0 );  /* Four-byte alignment */
  if( 0==*(char*)&byteOrderTest ){
    /* This is a big-endian machine */
    while( z<zEnd ){
      sum += *(unsigned*)z;
      z += 4;
    }
  }else{