title: wireshark lua string:byte() error
body: <p>I have a string problem when writing my lua dissector. My packet looks like:</p>
  
  <pre><code>0000   00 00 00 69 00 10 00 01 00 00 00 ed 00 00 00 0c
  0010   bf a6 5f ...
  </code></pre>
  
  <p>When debugging, the tvb looks the same</p>
  
  <p><a href="https://i.stack.imgur.com/I397R.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/I397R.png" alt="enter image description here"></a></p>
  
  <p>The byte at offset <strong>0x10</strong> is <strong>0xbf</strong>, but in my dissector function I got different result, here' my code:</p>
  
  <pre><code>local str = buf(0x10):string()
  local x = string.byte(str, 1)
  </code></pre>
  
  <p>the variable <strong>x</strong> should be <strong>0xbf</strong>, but it's <strong>0xef</strong>, and some other offset are also 0xef:</p>
  
  <pre><code>local str = buf(0x11):string()
  local x = string.byte(str, 1) -- also get 0xef, should be 0xa6
  
  local str = buf(11):string()
  local x = string.byte(str, 1) -- also get 0xef, should be 0xed
  </code></pre>
  
  <p>Seems big values will always get 0xef as result, like 0xa6/0xbf/0xed...</p>
  
  <p>And small values will be correct, like 0x69/0x5f/0x0c...</p>
  
  <p>I'm using the latest wireshark 2.0, is this a bug?</p>