title: Index or range of second ocurence of bytes in file
body: <p>I'm trying to find the second occurence of a byte pattern in a file. I can sucessfully find the first with:</p>
  
  <p><code>let mtrkChunk = Data(bytes: [0x4D, 0x54, 0x72, 0x6B] as [UInt8], count: 4)</code>
  and then
  <code>let mtrkChRng = data.range(of: mtrkChunk)</code></p>
  
  <p>But can't work out how to make it match the second occurence instead. Any help as ever would be appreciated</p>