title: memcpy with startIndex?
body: <p>I wish to copy content of specific length from one buffer to another from a specific starting point. I checked <code>memcpy()</code> but it takes only the length of content to be copied while I want to specify the starting index too.</p>
  
  <p>Is there any function which can do this or is there any good approach to do it with the existing <code>memcpy</code> function?</p>