 first a
bytevector of length &rsquo;size&rsquo; containing the block of data read, second
the size of the block of data placed in the bytevector and third an
escape continuation.  The value passed as the size of the block of
data placed in the bytevector will always be the same as &rsquo;size&rsquo; unless
end-of-file has been encountered after receiving only a partial block
of data.
</p>
<p>The event loop will not be blocked by this procedure even if only
individual bytes are available at any one time (al