title: How does one find the start of the "Central Directory" in zip files?
body: <p><a href="http://en.wikipedia.org/wiki/ZIP_(file_format)" rel="noreferrer">Wikipedia has an excellent description of the ZIP file format</a>, but the "central directory" structure is confusing to me. Specifically this:</p>
  
  <blockquote>
    <p>This ordering allows a ZIP file to be created in one pass, but it is usually decompressed by first reading the central directory at the end.</p>
  </blockquote>
  
  <p>The problem is that even the trailing header for the central directory is variable length. How then, can someone get the start of the central directory to parse?</p>
  
  <p>(Oh, and I did spend some time looking at APPNOTE.TXT in vain before coming here and asking :P)</p>