C++ calculating size
<p>Consider a packet which consists of header followed by multiple values. If <code>hdr</code> points to the packet header and <code>lastValue</code> points to last value in the packet. can you please explain me the following code:</p>

<pre><code>size_t  calcSize   = (lastValue - (char *)hdr); 
</code></pre>

<p>What size does <code>calcSize</code> denote of the packet. In other words what are the start and end locations that is being considered for this size. Thanks,</p>
