csapp2e 家庭作业2.63

 3 int sra(int x,int k)
  4 {
  5     int xsrl = (unsigned)x >> k;
  6     int w = sizeof(int)*8;
  7     int mask = ((1<<k)-1) << (w-k);
  8     int lmb = x&(1<<(w-1));
  9     lmb&& (xsrl |= mask);
 10     return xsrl;
 11 }
 12 int srl(unsigned x,int k)
 13 {
 14     unsigned xsra = (int)x >> k;
 15     int w =sizeof(unsigned)*8;
 16     int lmb = x & (1<<(w-1));
 17     int mask = (1<<(w-k))-1;
 18     lmb && mask && (xsra &= mask);
 19     return xsra;
 20 }