d decode integers to
    and from byte sequences.</p>

<p>All following functions raise <code class="code">Invalid_argument</code> if the space
    needed at index <code class="code">i</code> to decode or encode the integer is not
    available.</p>

<p>Little-endian (resp. big-endian) encoding means that least
    (resp. most) significant bytes are stored first.  Big-endian is
    also known as network byte order.  Native-endian encoding is
    either little-endian or big-endian depending on <a href="Sys.h