javascript to generate crc code for thumbnails.

Fiasco · 2009-09-22 22:57

Would it be possible to get a javascript function for AJAX purposes that can take the path/filename and convert it to the correct thumbnail (tbn) filename?

Fiasco · 2009-09-22 23:14

Or, add the crc of the thumb to the database?

Fiasco · 2009-09-23 18:12

this what is listed on the thumbnail wiki page for generating the thumb crc/name.

Code:

public string Hash(string input)

{

   uint m_crc = 0xffffffff;

   System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();

   bytes = encoding.GetBytes(input.ToLower());

   foreach (byte myByte in bytes)

   {

       m_crc ^= ((uint)(myByte) << 24);

       for (int i = 0; i < 8; i++)

       {

           if ((System.Convert.ToUInt32(m_crc) & 0x80000000) == 0x80000000)

           {

               m_crc = (m_crc << 1) ^ 0x04C11DB7;

           }

           else

           {

               m_crc <<= 1;

           }

       }

   }

   return String.Format("{0:x8}", m_crc);

}

Here is my (failed) javascript

Code:

function findCRC( string ) {

            var CRC = 0xffffffff;

            for ( var j = 0; j < string.length; j++ ) {

                var c = string.charCodeAt(j);

                CRC ^= c << 24;

                for (var i = 0; i < 8; i++) {

                    if ( CRC & 0x800000000 )

                      CRC = (CRC <<  1) ^ 0x04C11DB7;

                    else

                      CRC <<=1;

                }

             }

             return CRC.toString(16);

}

C:\Movies\Singles.iso generates -43a5d0a9 (should generate 405f3ec2)
C:\Movies\Wag The Dog.iso generates -1e3e89c7 (should generate 30d882a2)

Help!

Fiasco · 2009-09-23 20:34

OK I've gotten closer!!! It returns some values correctly! Some are not.

Any suggestions I'll gratefully accept!!

FindCRC( "C:\Movies\Wag The Dog.iso" );
returns 30d882a2 (CORRECT!)
FindCRC( "C:\Movies\The Wedding Singer.iso");
returns 4bbcf3ea (CORRECT!)
FindCRC("C:\Movies\Singles.iso");
returns 405f3ec2 (CORRECT!)
FindCRC("C:\Movies\The Adventures of Ford Fairlane.iso");
returns -a2a374c (WRONG!)
FindCRC("C:\Movies\Identity.iso");
returns -6ed4f2f4 (WRONG!);

Code:

Number.prototype.unsign = function(bytes) {

  return this >= 0 ? this : Math.pow(256, bytes || 4) + this;

};

function FindCRC(data) {        // computes crc value

  var CRC=0xffffffff;

  data = data.toLowerCase();

  for (var j=0; j<data.length; j++) {

    var c = data.charCodeAt(j);

    CRC ^= c << 24;

    for(var i = 0; i<8; i++) {

        if( CRC.unsign(8) & 0x80000000 ) {

          CRC = (CRC << 1) ^ 0x04C11DB7;

        } else{

          CRC <<= 1;

        }

     }

  }

  return CRC.toString(16);

}

Fiasco · 2009-09-23 21:09

sooo close argghhhhh

Fiasco · 2009-09-23 21:43

HOOORAY!!!!!

How to convert the path + filename to the CRC code for thumbnails in javascript.

Call from j

var thumbcrc = FindCRC( "C:\Movie\Adventures Of Ford Fairlane.iso");

Code:

Number.prototype.unsign = function(bytes) {

  return this >= 0 ? this : Math.pow(256, bytes || 4) + this;

};

function FindCRC(data) {

  var CRC=0xffffffff;

  data = data.toLowerCase();

  for (var j=0; j<data.length; j++) {

    var c = data.charCodeAt(j);

    CRC ^= c << 24;

    for(var i = 0; i<8; i++) {

        if(CRC.unsign(8) & 0x80000000) {

          CRC = (CRC << 1) ^ 0x04C11DB7;

        } else{

          CRC <<= 1;

        }

     }

  }

  if ( CRC < 0 ) CRC = CRC>>>0;

  return CRC.toString(16);

}

kevbrown · 2009-11-19 06:39

I'm wanting to do the same thing in PHP. I want to do some tinkering with a web based library editor, but I can't for the life of me figure this out. There's a crc32 function within PHP, but that doesn't return the right value, so I wrap dechex to convert to hex, still no dice. Based on what I "think" your function is doing, I'm then performing this on the lower case string.

Also - what path does it use, the full path to the file, just the file name? How does it work with stacked items? Have you tried that?

Fiasco · 2009-11-19 07:02

full path to the filename as in the example

tjpoe · 2009-12-18 20:45

did you ever figure this out in PHP? i'm trying to do the same thing.

tried : crc32 ( $path . $file ).
also tried dechex( crc32( $path . $file ) )

but both were a no go.

forumReader · 2010-03-21 02:40

Fiasco Wrote:HOOORAY!!!!!

How to convert the path + filename to the CRC code for thumbnails in javascript.

Call from j

var thumbcrc = FindCRC( "C:\Movie\Adventures Of Ford Fairlane.iso");

Code:

Number.prototype.unsign = function(bytes) { return this >= 0 ? this : Math.pow(256, bytes || 4) + this; }; function FindCRC(data) { var CRC=0xffffffff; data = data.toLowerCase(); for (var j=0; j<data.length; j++) { var c = data.charCodeAt(j); CRC ^= c << 24; for(var i = 0; i<8; i++) { if(CRC.unsign(8) & 0x80000000) { CRC = (CRC << 1) ^ 0x04C11DB7; } else{ CRC <<= 1; } } } if ( CRC < 0 ) CRC = CRC>>>0; return CRC.toString(16); }

Hi, very great job done. Laugh

but when i try the exambles on xbmc:wiki- Thumbnails, some get the wrong hash. I tried some from my own and 2 did not work.

123456789 returns 376e6e7
should return:
0376e6e7

F:\Videos\Nosferatu.avi returns 2a6ec78d
-> correct

smb://user:pass@server/share/directory/ returns c5559f13
-> correct

smb://user:pass@server/share/directory/file.ext retutns 8ce36055
-> correct

im trying to fix it but its very hard..

on smb:// devices it works fine:
smb://data:data@michi_lap/e/musik/paul kalkbrenner - berlin calling bonus/01 aaron.mp3
should return:
20ae3cc1

but on local device:
e:\musik\paul kalkbrenner - berlin calling bonus\01 aaron.mp3

it returns: c8caa9e4

but should return: 614b6c10

some other examble:
e:\\musik\\clueso - gute musik\\clueso - gute musik - 15 - vergessen ist so leicht - maskulin.mp3
returns: c17f5fd6
should return: e09ff0ca

ore did id did something wrong?

Fiasco Senior Member Posts: 159 Joined: May 2009 Reputation: 0	2009-09-22 22:57 Post: #1 Would it be possible to get a javascript function for AJAX purposes that can take the path/filename and convert it to the correct thumbnail (tbn) filename?
	find quote

Fiasco Senior Member Posts: 159 Joined: May 2009 Reputation: 0	2009-09-22 23:14 Post: #2 Or, add the crc of the thumb to the database?
	find quote

Fiasco Senior Member Posts: 159 Joined: May 2009 Reputation: 0	2009-09-23 21:09 Post: #5 sooo close argghhhhh
	find quote

Fiasco Senior Member Posts: 159 Joined: May 2009 Reputation: 0	2009-11-19 07:02 Post: #8 full path to the filename as in the example
	find quote

tjpoe Junior Member Posts: 48 Joined: Nov 2009 Reputation: 0	2009-12-18 20:45 Post: #9 did you ever figure this out in PHP? i'm trying to do the same thing. tried : crc32 ( $path . $file ). also tried dechex( crc32( $path . $file ) ) but both were a no go.
	find quote