tcher checksum uses 255, which is not prime and which also
      makes the Fletcher check insensitive to single byte changes 0 &lt;-&gt;
      255.)

      The sum s1 is initialized to 1 instead of zero to make the length
      of the sequence part of s2, so that the length does not have to be
      checked separately. (Any sequence of zeroes has a Fletcher
      checksum of zero.)








<span class="grey">Deutsch &amp; Gailly             Informational                      [Page 9]</span></pre>
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