bytes in the format to compute a checksum over
</li>
</ul>
</li>
</ul>
</section>
<section id="sec-7-2-2" >

<h4>Transformations</h4>
<ul class="org-ul">
<li>Transformations are a pair of functions that modify streams.
</li>
<li>Example: offset transform
</li>
<li>Parsing function extracts a substream starting at an offset from a stream
</li>
</ul>
<pre class="example">
int offset_u32_parse(NailArena *tmp, NailStream *out_fragment, NailStream *in_whole, 
                      const uint32_t *offset);
</pre>