Explanation, please!

[Douglas C. Schmidt]

The following piece of wonderful obscurity comes from Stroustup's
C++ Programming Language book, page 100:

void send(int *to,int *from, int count) {
   int n = (count + 7) / 8;
   
   switch(count % 8) {
      case 0:  do { *to++ = *from++;
      case 7:       *to++ = *from++;
      case 6:       *to++ = *from++;
      case 5:       *to++ = *from++;
      case 4:       *to++ = *from++;
      case 3:       *to++ = *from++;
      case 2:       *to++ = *from++;
      case 1:       *to++ = *from++;
               } while (--n > 0);
   }

}

Now, much to my surprise, this is not only valid C++, it is also valid C!
Could some one please explain to me why this is so?  It seems like
the case 7-1 labels are actually nested inside the do {} while loop,
and thus not in the scope of the switch (should a break statement exit
both the switch and the loop, or just one?!?!).

Finally, Stroustrup asks the rhetorical question ``why would anyone
want to write something like this.''  Any guesses?!

thanks,

   Doug Schmidt
--
Douglas Schmidt
"If our behavior is strict, we do not need fun." -Zippy th' Pinhead
"If our behavior is struct, we do not need defun." -Anon