code: func chunksOf(in []byte) (stringExpression []byte) {
  	var multiParts [][]byte
  	rs := rollsum.New()
  	const nBits = 9 // ~512 byte chunks
  	last := 0
  	for i, b := range in {
  		rs.Roll(b)
  		if rs.OnSplitWithBits(nBits) || i == len(in)-1 {
  			raw := in[last : i+1] // inclusive
  			last = i + 1
  			s1 := sha1.New()
  			s1.Write(raw)
  			sha1hex := fmt.Sprintf("%x", s1.Sum(nil))[:8]
  			writeChunkFile(sha1hex, raw)
  			multiParts = append(multiParts, []byte(fmt.Sprintf("chunkpkg.C%s", sha1hex)))
  		}
  	}
  	return bytes.Join(multiParts, []byte(",\n\t"))
  }
docs: // chunksOf takes a (presumably large) file's uncompressed input,
  // rolling-checksum splits it into ~514 byte chunks, compresses each,
  // base64s each, and writes chunk files out, with each file just
  // defining an exported fileembed.Opener variable named C<xxxx> where
  // xxxx is the first 8 lowercase hex digits of the SHA-1 of the chunk
  // value pre-compression.  The return value is a Go expression
  // referencing each of those chunks concatenated together.