Question about StellarisWare, SW-RDK-S2E, stellarisif.c

static err_t
stellarisif_transmit(struct netif *netif, struct pbuf *p)
{
  int iBuf;
  unsigned char *pucBuf;
  unsigned long *pulBuf;
  struct pbuf *q;
  int iGather;
  unsigned long ulGather;
  unsigned char *pucGather;

........................... [omitted]

    /* Initialze a long pointer into the pbuf for 32-bit access. */
    pulBuf = (unsigned long *)&pucBuf[iBuf];

    /**
     * Copy words of pbuf data into the Tx FIFO, but don't go past
     * the end of the pbuf.
     *
     */
    while((iBuf + 4) <= q->len) {
      HWREG(ETH_BASE + MAC_O_DATA) = *pulBuf++;
      iBuf += 4;
    }

  __packed unsigned long *pulBuf;