question about func in Checksum.c

[Zheng Yuan {ZYUAN1}]

Hi, all

I have a question about the func static u16 ipsum_calc_block(u16 *x,
unsigned len, u16 sum)

I guess we dont need the first len >>= 1 i know we want to move 32 bits at
one time, so second len >>= 1 can do it. The first one is redundant.

static u16 ipsum_calc_block(u16 *x, unsigned len, u16 sum) {
  int rest;
  u32 tmp, *xx;
  ASSERT(!(len % 2));
  if (!len)
    return sum;
  len >>= 1;
  if ((unsigned long) x & 2)  /* Align to 32-bit boundary, use x's address
*/
    {
      sum = add16(sum, *x++);
      len--;
    }
  rest = len & 1;
  len >>= 1;
  tmp = 0;
  xx = (u32 *) x;
  while (len)
    {
      tmp = add32(tmp, *xx++);
      len--;
    }
  sum = add16(sum, add16(tmp & 0xffff, tmp >> 16U));
  if (rest)
    sum = add16(sum, *(u16 *) xx);
  return sum;
}