title: C++ : convert uint64_t to unsigned char array
body: <p>I need to convert for exemple this number : 281474976710655 to a unsigned char array like this one :</p>
  
  <pre><code>unsigned char value[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
  </code></pre>
  
  <p>I try to memcpy and other techniques but i didn't get the correct value back, always random hex...</p>
  
  <p>I'm not a c++ developer so thanks to explain if you can.</p>
  
  <p>Thanks a lot, bye !</p>