title: What is memmove() alternative when I know the overlapping side?
body: <p>I want know what the fastest function for copy n bytes from *source to *destination, when 
  <code>*destination = *source + k</code>, and <code>k is netural or zero</code>.</p>
  
  <p>The memcpy() function has undefind behavior for overlapping.</p>
  
  <p>The memmove() function is not the best, since it has to check the overlapping side.</p>
  
  <p>There is another function that is optimal to my case?</p>
  
  <p>Thanks in advance!</p>