Smarty foreach / shuffle/random and limit

I want to get items foreach, shuffle them and limit the output to 4 items.

i've this. (displays all items)

{content block_id=27}
{if $_content_27|count >0}
{foreach name=aussen item=box_data from=$_content_27}
  <article class="news_row_article col-lg-3">
          <div><img src="images/ImgResponsive_Placeholder.png" alt=""/></div>
          <h3 class="news_row_headline">{$box_data.content_heading}</h3>
          <p class="news_row_content">{$box_data.content_body}</p>
</article>
    {/foreach}
{/if}

i've found this

{foreach array_rand($a_firm_display,5) as $i} 
<a href="{$smarty.const.HOST}{$a_firm_display[$i].url_rewriting}"><img src="{$a_firm_display[$i].firm_logo}" /></a> 
{/foreach}

or this Generate distinct smarty random numbers

    {assign var="distinct_numbers" value=array_fill(1,15,'x')}
{assign var="distinct_numbers" value=array_keys($distinct_numbers)}
{assign var="x" value=shuffle($distinct_numbers)}

{* result *}

{foreach from=$distinct_numbers item="value"}
    {$value} |
{/foreach}

hm..somehow get the items from $_content_27 put them into array, output, and limit them ?

any ideas ?