Uniquely identify a file without downloading
<p>So the base project is this... </p>

<p>I am trying to write a server application that will download and hash files off of a website. </p>

<p>The reason for this is so that I can blacklist particular files that are re-uploaded under different names or provide further descriptions as to what a file really is. These files are 0.1KB - 10.00MB and many. If I could detect within a reasonable ballpark figure a file is already hashed I could return the hash rather then download the entire file and send the results. </p>

<p>My temporary solution is a JavaScript add-on that does it on the spot. This causes temporary freezes and is too redundant for my liking. My goal is to make this good enough to share with the public; The current method is far from. </p>

<p>My skill set in programming is very wide yet not professional or polished in any individual so a library or examples are highly appreciated. </p>

<hr>

<p>A snip-it of my java-script code is this... </p>

<pre><code>    $('.tablesorter tbody tr').each(function(index) {
        var href = 'http:' + $(this).find("td a:eq(0)").attr('href');
        var MD5  = "";
        $.get(href, function(data) {
            MD5 = calcMD5(data);
            $(".tablesorter tbody tr:eq("+index+") td:eq(3)").text(MD5); 
         });
    });
</code></pre>

<p>This works great, does what it needs to. However I'd like to have a server do this so that a file only needs to be hashed a single time. </p>
