How to calculate crc16 in php

Question

I need help in converting CRC code written in Ojective C to PHP. The following is the Objective C code

static UInt16 CRC16_Table[] =
   {    0x0000, 0x2110, 0x4220, 0x6330, 0x8440, 0xa550, 0xc660, 0xe770,
    0x0881, 0x2991, 0x4aa1, 0x6bb1, 0x8cc1, 0xadd1, 0xcee1, 0xeff1,
    0x3112, 0x1002, 0x7332, 0x5222, 0xb552, 0x9442, 0xf772, 0xd662,
    0x3993, 0x1883, 0x7bb3, 0x5aa3, 0xbdd3, 0x9cc3, 0xfff3, 0xdee3,
    0x6224, 0x4334, 0x2004, 0x0114, 0xe664, 0xc774, 0xa444, 0x8554,
    0x6aa5, 0x4bb5, 0x2885, 0x0995, 0xeee5, 0xcff5, 0xacc5, 0x8dd5,
    0x5336, 0x7226, 0x1116, 0x3006, 0xd776, 0xf666, 0x9556, 0xb446,
    0x5bb7, 0x7aa7, 0x1997, 0x3887, 0xdff7, 0xfee7, 0x9dd7, 0xbcc7,
    0xc448, 0xe558, 0x8668, 0xa778, 0x4008, 0x6118, 0x0228, 0x2338,
    0xccc9, 0xedd9, 0x8ee9, 0xaff9, 0x4889, 0x6999, 0x0aa9, 0x2bb9,
    0xf55a, 0xd44a, 0xb77a, 0x966a, 0x711a, 0x500a, 0x333a, 0x122a,
    0xfddb, 0xdccb, 0xbffb, 0x9eeb, 0x799b, 0x588b, 0x3bbb, 0x1aab,
    0xa66c, 0x877c, 0xe44c, 0xc55c, 0x222c, 0x033c, 0x600c, 0x411c,
    0xaeed, 0x8ffd, 0xeccd, 0xcddd, 0x2aad, 0x0bbd, 0x688d, 0x499d,
    0x977e, 0xb66e, 0xd55e, 0xf44e, 0x133e, 0x322e, 0x511e, 0x700e,
    0x9fff, 0xbeef, 0xdddf, 0xfccf, 0x1bbf, 0x3aaf, 0x599f, 0x788f,
    0x8891, 0xa981, 0xcab1, 0xeba1, 0x0cd1, 0x2dc1, 0x4ef1, 0x6fe1,
    0x8010, 0xa100, 0xc230, 0xe320, 0x0450, 0x2540, 0x4670, 0x6760,
    0xb983, 0x9893, 0xfba3, 0xdab3, 0x3dc3, 0x1cd3, 0x7fe3, 0x5ef3,
    0xb102, 0x9012, 0xf322, 0xd232, 0x3542, 0x1452, 0x7762, 0x5672,
    0xeab5, 0xcba5, 0xa895, 0x8985, 0x6ef5, 0x4fe5, 0x2cd5, 0x0dc5,
    0xe234, 0xc324, 0xa014, 0x8104, 0x6674, 0x4764, 0x2454, 0x0544,
    0xdba7, 0xfab7, 0x9987, 0xb897, 0x5fe7, 0x7ef7, 0x1dc7, 0x3cd7,
    0xd326, 0xf236, 0x9106, 0xb016, 0x5766, 0x7676, 0x1546, 0x3456,
    0x4cd9, 0x6dc9, 0x0ef9, 0x2fe9, 0xc899, 0xe989, 0x8ab9, 0xaba9,
    0x4458, 0x6548, 0x0678, 0x2768, 0xc018, 0xe108, 0x8238, 0xa328,
    0x7dcb, 0x5cdb, 0x3feb, 0x1efb, 0xf98b, 0xd89b, 0xbbab, 0x9abb,
    0x754a, 0x545a, 0x376a, 0x167a, 0xf10a, 0xd01a, 0xb32a, 0x923a,
    0x2efd, 0x0fed, 0x6cdd, 0x4dcd, 0xaabd, 0x8bad, 0xe89d, 0xc98d,
    0x267c, 0x076c, 0x645c, 0x454c, 0xa23c, 0x832c, 0xe01c, 0xc10c,
    0x1fef, 0x3eff, 0x5dcf, 0x7cdf, 0x9baf, 0xbabf, 0xd98f, 0xf89f,
    0x176e, 0x367e, 0x554e, 0x745e, 0x932e, 0xb23e, 0xd10e, 0xf01e
   };


   +(SInt16) CalculateCRC16 : (Byte*)buffer : (UInt16) length
   {
    UInt32   crc=0;

    while (length--)
        crc = ((crc>>8) & 0xff) ^ *(CRC16_Table + ((*buffer++ ^ crc) & 0xff));

    return((SInt16)crc);
   }

and the following is the code I've written so far in php

$CRC16_Table = array
        (   0x0000, 0x2110, 0x4220, 0x6330, 0x8440, 0xa550, 0xc660, 0xe770,
            0x0881, 0x2991, 0x4aa1, 0x6bb1, 0x8cc1, 0xadd1, 0xcee1, 0xeff1,
            0x3112, 0x1002, 0x7332, 0x5222, 0xb552, 0x9442, 0xf772, 0xd662,
            0x3993, 0x1883, 0x7bb3, 0x5aa3, 0xbdd3, 0x9cc3, 0xfff3, 0xdee3,
            0x6224, 0x4334, 0x2004, 0x0114, 0xe664, 0xc774, 0xa444, 0x8554,
            0x6aa5, 0x4bb5, 0x2885, 0x0995, 0xeee5, 0xcff5, 0xacc5, 0x8dd5,
            0x5336, 0x7226, 0x1116, 0x3006, 0xd776, 0xf666, 0x9556, 0xb446,
            0x5bb7, 0x7aa7, 0x1997, 0x3887, 0xdff7, 0xfee7, 0x9dd7, 0xbcc7,
            0xc448, 0xe558, 0x8668, 0xa778, 0x4008, 0x6118, 0x0228, 0x2338,
            0xccc9, 0xedd9, 0x8ee9, 0xaff9, 0x4889, 0x6999, 0x0aa9, 0x2bb9,
            0xf55a, 0xd44a, 0xb77a, 0x966a, 0x711a, 0x500a, 0x333a, 0x122a,
            0xfddb, 0xdccb, 0xbffb, 0x9eeb, 0x799b, 0x588b, 0x3bbb, 0x1aab,
            0xa66c, 0x877c, 0xe44c, 0xc55c, 0x222c, 0x033c, 0x600c, 0x411c,
            0xaeed, 0x8ffd, 0xeccd, 0xcddd, 0x2aad, 0x0bbd, 0x688d, 0x499d,
            0x977e, 0xb66e, 0xd55e, 0xf44e, 0x133e, 0x322e, 0x511e, 0x700e,
            0x9fff, 0xbeef, 0xdddf, 0xfccf, 0x1bbf, 0x3aaf, 0x599f, 0x788f,
            0x8891, 0xa981, 0xcab1, 0xeba1, 0x0cd1, 0x2dc1, 0x4ef1, 0x6fe1,
            0x8010, 0xa100, 0xc230, 0xe320, 0x0450, 0x2540, 0x4670, 0x6760,
            0xb983, 0x9893, 0xfba3, 0xdab3, 0x3dc3, 0x1cd3, 0x7fe3, 0x5ef3,
            0xb102, 0x9012, 0xf322, 0xd232, 0x3542, 0x1452, 0x7762, 0x5672,
            0xeab5, 0xcba5, 0xa895, 0x8985, 0x6ef5, 0x4fe5, 0x2cd5, 0x0dc5,
            0xe234, 0xc324, 0xa014, 0x8104, 0x6674, 0x4764, 0x2454, 0x0544,
            0xdba7, 0xfab7, 0x9987, 0xb897, 0x5fe7, 0x7ef7, 0x1dc7, 0x3cd7,
            0xd326, 0xf236, 0x9106, 0xb016, 0x5766, 0x7676, 0x1546, 0x3456,
            0x4cd9, 0x6dc9, 0x0ef9, 0x2fe9, 0xc899, 0xe989, 0x8ab9, 0xaba9,
            0x4458, 0x6548, 0x0678, 0x2768, 0xc018, 0xe108, 0x8238, 0xa328,
            0x7dcb, 0x5cdb, 0x3feb, 0x1efb, 0xf98b, 0xd89b, 0xbbab, 0x9abb,
            0x754a, 0x545a, 0x376a, 0x167a, 0xf10a, 0xd01a, 0xb32a, 0x923a,
            0x2efd, 0x0fed, 0x6cdd, 0x4dcd, 0xaabd, 0x8bad, 0xe89d, 0xc98d,
            0x267c, 0x076c, 0x645c, 0x454c, 0xa23c, 0x832c, 0xe01c, 0xc10c,
            0x1fef, 0x3eff, 0x5dcf, 0x7cdf, 0x9baf, 0xbabf, 0xd98f, 0xf89f,
            0x176e, 0x367e, 0x554e, 0x745e, 0x932e, 0xb23e, 0xd10e, 0xf01e
        );

   function CalculateCRC16($strMessage)
   {
      $hexdata = pack('H*',$strMessage);
        $nLength = strlen($hexdata);
        $crc = 0xFFFF;
        $pos = 0;
        while($nLength > 0)
        {
            $crc = ($crc >> 8) ^ $CRC16_Table[($crc ^ ord($hexdata[$pos])) &       0xFF];
            $nLength--;
            $pos++;
        }
        return ~$crc;
   }

Where $strMessage contains packed values, but it does not give the correct result.

Any help will be highly appreciated.

PHP does integers oddly. You're probably hitting an overflow and PHP's transforming it silently into a float. Do you *need* CRC16? The [hash extension](http://php.net/book.hash) includes implementations of CRC32, CRC32B, Adler32 and more... — Charles, Dec 24 '12 at 07:40
yea I need CRC16, because we are using it throughout our architeture. — Amjad khan, Dec 24 '12 at 07:43
A correct crc16 algo will never return a value more that 16 bits [max value of 65,536]. This will never overflow a PHP int which is typically 32 bits, with the only exception of 64 bit ints on systems compiled for 64 bit architectures. Any overflow issues will be specifically due to an incorrect crc16 implementation. — JSON, Jun 18 '15 at 07:34
@Charles - PHP numbers are typicaly unsigned 32 bit ints. Although this may seem odd to some, it is well defined and will always represent a value of -2,147,483,648 through 2,147,483,647. PHP ints on 64 bit systems will be unsigned 64 bit ints if PHP was specifically compiled to as such. This might be confusing to some, but it is well documented and should be easy to understand. — JSON, Jun 18 '15 at 07:34

Esailija · Accepted Answer · 2012-12-24T08:05:06.270

This seems to work, tested with several values against this website for CRC-16-CCITT

Note that it uses PHP strings as direct byte buffers, because it's PHP's closest equivalent to byte[]

<?php

class CRC16 {
    private static $CRC16_Table = array
        (   0x0000, 0x2110, 0x4220, 0x6330, 0x8440, 0xa550, 0xc660, 0xe770,
            0x0881, 0x2991, 0x4aa1, 0x6bb1, 0x8cc1, 0xadd1, 0xcee1, 0xeff1,
            0x3112, 0x1002, 0x7332, 0x5222, 0xb552, 0x9442, 0xf772, 0xd662,
            0x3993, 0x1883, 0x7bb3, 0x5aa3, 0xbdd3, 0x9cc3, 0xfff3, 0xdee3,
            0x6224, 0x4334, 0x2004, 0x0114, 0xe664, 0xc774, 0xa444, 0x8554,
            0x6aa5, 0x4bb5, 0x2885, 0x0995, 0xeee5, 0xcff5, 0xacc5, 0x8dd5,
            0x5336, 0x7226, 0x1116, 0x3006, 0xd776, 0xf666, 0x9556, 0xb446,
            0x5bb7, 0x7aa7, 0x1997, 0x3887, 0xdff7, 0xfee7, 0x9dd7, 0xbcc7,
            0xc448, 0xe558, 0x8668, 0xa778, 0x4008, 0x6118, 0x0228, 0x2338,
            0xccc9, 0xedd9, 0x8ee9, 0xaff9, 0x4889, 0x6999, 0x0aa9, 0x2bb9,
            0xf55a, 0xd44a, 0xb77a, 0x966a, 0x711a, 0x500a, 0x333a, 0x122a,
            0xfddb, 0xdccb, 0xbffb, 0x9eeb, 0x799b, 0x588b, 0x3bbb, 0x1aab,
            0xa66c, 0x877c, 0xe44c, 0xc55c, 0x222c, 0x033c, 0x600c, 0x411c,
            0xaeed, 0x8ffd, 0xeccd, 0xcddd, 0x2aad, 0x0bbd, 0x688d, 0x499d,
            0x977e, 0xb66e, 0xd55e, 0xf44e, 0x133e, 0x322e, 0x511e, 0x700e,
            0x9fff, 0xbeef, 0xdddf, 0xfccf, 0x1bbf, 0x3aaf, 0x599f, 0x788f,
            0x8891, 0xa981, 0xcab1, 0xeba1, 0x0cd1, 0x2dc1, 0x4ef1, 0x6fe1,
            0x8010, 0xa100, 0xc230, 0xe320, 0x0450, 0x2540, 0x4670, 0x6760,
            0xb983, 0x9893, 0xfba3, 0xdab3, 0x3dc3, 0x1cd3, 0x7fe3, 0x5ef3,
            0xb102, 0x9012, 0xf322, 0xd232, 0x3542, 0x1452, 0x7762, 0x5672,
            0xeab5, 0xcba5, 0xa895, 0x8985, 0x6ef5, 0x4fe5, 0x2cd5, 0x0dc5,
            0xe234, 0xc324, 0xa014, 0x8104, 0x6674, 0x4764, 0x2454, 0x0544,
            0xdba7, 0xfab7, 0x9987, 0xb897, 0x5fe7, 0x7ef7, 0x1dc7, 0x3cd7,
            0xd326, 0xf236, 0x9106, 0xb016, 0x5766, 0x7676, 0x1546, 0x3456,
            0x4cd9, 0x6dc9, 0x0ef9, 0x2fe9, 0xc899, 0xe989, 0x8ab9, 0xaba9,
            0x4458, 0x6548, 0x0678, 0x2768, 0xc018, 0xe108, 0x8238, 0xa328,
            0x7dcb, 0x5cdb, 0x3feb, 0x1efb, 0xf98b, 0xd89b, 0xbbab, 0x9abb,
            0x754a, 0x545a, 0x376a, 0x167a, 0xf10a, 0xd01a, 0xb32a, 0x923a,
            0x2efd, 0x0fed, 0x6cdd, 0x4dcd, 0xaabd, 0x8bad, 0xe89d, 0xc98d,
            0x267c, 0x076c, 0x645c, 0x454c, 0xa23c, 0x832c, 0xe01c, 0xc10c,
            0x1fef, 0x3eff, 0x5dcf, 0x7cdf, 0x9baf, 0xbabf, 0xd98f, 0xf89f,
            0x176e, 0x367e, 0x554e, 0x745e, 0x932e, 0xb23e, 0xd10e, 0xf01e
        );

    public static function calculate( $buffer ) {
        $length = strlen($buffer);

        $crc = 0;
        $i = 0;
        while( $length-- ) {
            $crc = (( $crc >> 8) & 0xff) ^ (self::$CRC16_Table[(ord($buffer[$i++]) ^ $crc) & 0xFF]);
        }

        return (($crc & 0xFFFF) ^ 0x8000) - 0x8000;
    }    
}

echo CRC16::calculate( "\x74\x65\x73\x74" );

Can this code be used to check CRC 16 algorithm using polynom 0x8005 ? — Furqan S. Mahmoud, Jul 25 '20 at 10:31

score 8 · Answer 2 · answered Nov 13 '14 at 16:21

8

It is CRC-16 CCITT, may be it'll help you

<?php
function crc16($data)
 {
   $crc = 0xFFFF;
   for ($i = 0; $i < strlen($data); $i++)
   {
     $x = (($crc >> 8) ^ ord($data[$i])) & 0xFF;
     $x ^= $x >> 4;
     $crc = (($crc << 8) ^ ($x << 12) ^ ($x << 5) ^ $x) & 0xFFFF;
   }
   return $crc;
 }
?>

answered Nov 13 '14 at 16:21

Roman Kazanovskyi

2,295
1
19
21

Very late to this comment, but something is wrong if I use the number 99. Any ideas? I am using it in a QR code generator and it fails only with the number 99. – moo moo Dec 20 '20 at 18:03
how can I decode this? – vishal vanpariya Apr 05 '21 at 10:34

How to calculate crc16 in php

2 Answers2

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