<?php

/*

 * PHP QR Code encoder

 *

 * Reed-Solomon error correction support

 * 

 * Copyright (C) 2002, 2003, 2004, 2006 Phil Karn, KA9Q

 * (libfec is released under the GNU Lesser General Public License.)

 *

 * Based on libqrencode C library distributed under LGPL 2.1

 * Copyright (C) 2006, 2007, 2008, 2009 Kentaro Fukuchi <fukuchi@megaui.net>

 *

 * PHP QR Code is distributed under LGPL 3

 * Copyright (C) 2010 Dominik Dzienia <deltalab at poczta dot fm>

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 3 of the License, or any later version.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

 */

 

    class QRrsItem {

    

        public $mm;                  // Bits per symbol 

        public $nn;                  // Symbols per block (= (1<<mm)-1) 

        public $alpha_to = array();  // log lookup table 

        public $index_of = array();  // Antilog lookup table 

        public $genpoly = array();   // Generator polynomial 

        public $nroots;              // Number of generator roots = number of parity symbols 

        public $fcr;                 // First consecutive root, index form 

        public $prim;                // Primitive element, index form 

        public $iprim;               // prim-th root of 1, index form 

        public $pad;                 // Padding bytes in shortened block 

        public $gfpoly;

    

        //----------------------------------------------------------------------

        public function modnn($x)

        {

            while ($x >= $this->nn) {

                $x -= $this->nn;

                $x = ($x >> $this->mm) + ($x & $this->nn);

            }

            

            return $x;

        }

        

        //----------------------------------------------------------------------

        public static function init_rs_char($symsize, $gfpoly, $fcr, $prim, $nroots, $pad)

        {

            // Common code for intializing a Reed-Solomon control block (char or int symbols)

            // Copyright 2004 Phil Karn, KA9Q

            // May be used under the terms of the GNU Lesser General Public License (LGPL)



            $rs = null;

            

            // Check parameter ranges

            if($symsize < 0 || $symsize > 8)                     return $rs;

            if($fcr < 0 || $fcr >= (1<<$symsize))                return $rs;

            if($prim <= 0 || $prim >= (1<<$symsize))             return $rs;

            if($nroots < 0 || $nroots >= (1<<$symsize))          return $rs; // Can't have more roots than symbol values!

            if($pad < 0 || $pad >= ((1<<$symsize) -1 - $nroots)) return $rs; // Too much padding



            $rs = new QRrsItem();

            $rs->mm = $symsize;

            $rs->nn = (1<<$symsize)-1;

            $rs->pad = $pad;



            $rs->alpha_to = array_fill(0, $rs->nn+1, 0);

            $rs->index_of = array_fill(0, $rs->nn+1, 0);

          

            // PHP style macro replacement ;)

            $NN =& $rs->nn;

            $A0 =& $NN;

            

            // Generate Galois field lookup tables

            $rs->index_of[0] = $A0; // log(zero) = -inf

            $rs->alpha_to[$A0] = 0; // alpha**-inf = 0

            $sr = 1;

          

            for($i=0; $i<$rs->nn; $i++) {

                $rs->index_of[$sr] = $i;

                $rs->alpha_to[$i] = $sr;

                $sr <<= 1;

                if($sr & (1<<$symsize)) {

                    $sr ^= $gfpoly;

                }

                $sr &= $rs->nn;

            }

            

            if($sr != 1){

                // field generator polynomial is not primitive!

                $rs = NULL;

                return $rs;

            }



            /* Form RS code generator polynomial from its roots */

            $rs->genpoly = array_fill(0, $nroots+1, 0);

        

            $rs->fcr = $fcr;

            $rs->prim = $prim;

            $rs->nroots = $nroots;

            $rs->gfpoly = $gfpoly;



            /* Find prim-th root of 1, used in decoding */

            for($iprim=1;($iprim % $prim) != 0;$iprim += $rs->nn)

            ; // intentional empty-body loop!

            

            $rs->iprim = (int)($iprim / $prim);

            $rs->genpoly[0] = 1;

            

            for ($i = 0,$root=$fcr*$prim; $i < $nroots; $i++, $root += $prim) {

                $rs->genpoly[$i+1] = 1;



                // Multiply rs->genpoly[] by  @**(root + x)

                for ($j = $i; $j > 0; $j--) {

                    if ($rs->genpoly[$j] != 0) {

                        $rs->genpoly[$j] = $rs->genpoly[$j-1] ^ $rs->alpha_to[$rs->modnn($rs->index_of[$rs->genpoly[$j]] + $root)];

                    } else {

                        $rs->genpoly[$j] = $rs->genpoly[$j-1];

                    }

                }

                // rs->genpoly[0] can never be zero

                $rs->genpoly[0] = $rs->alpha_to[$rs->modnn($rs->index_of[$rs->genpoly[0]] + $root)];

            }

            

            // convert rs->genpoly[] to index form for quicker encoding

            for ($i = 0; $i <= $nroots; $i++)

                $rs->genpoly[$i] = $rs->index_of[$rs->genpoly[$i]];



            return $rs;

        }

        

        //----------------------------------------------------------------------

        public function encode_rs_char($data, &$parity)

        {

            $MM       =& $this->mm;

            $NN       =& $this->nn;

            $ALPHA_TO =& $this->alpha_to;

            $INDEX_OF =& $this->index_of;

            $GENPOLY  =& $this->genpoly;

            $NROOTS   =& $this->nroots;

            $FCR      =& $this->fcr;

            $PRIM     =& $this->prim;

            $IPRIM    =& $this->iprim;

            $PAD      =& $this->pad;

            $A0       =& $NN;



            $parity = array_fill(0, $NROOTS, 0);



            for($i=0; $i< ($NN-$NROOTS-$PAD); $i++) {

                

                $feedback = $INDEX_OF[$data[$i] ^ $parity[0]];

                if($feedback != $A0) {      

                    // feedback term is non-zero

            

                    // This line is unnecessary when GENPOLY[NROOTS] is unity, as it must

                    // always be for the polynomials constructed by init_rs()

                    $feedback = $this->modnn($NN - $GENPOLY[$NROOTS] + $feedback);

            

                    for($j=1;$j<$NROOTS;$j++) {

                        $parity[$j] ^= $ALPHA_TO[$this->modnn($feedback + $GENPOLY[$NROOTS-$j])];

                    }

                }

                

                // Shift 

                array_shift($parity);

                if($feedback != $A0) {

                    array_push($parity, $ALPHA_TO[$this->modnn($feedback + $GENPOLY[0])]);

                } else {

                    array_push($parity, 0);

                }

            }

        }

    }

    

    //##########################################################################

    

    class QRrs {

    

        public static $items = array();

        

        //----------------------------------------------------------------------

        public static function init_rs($symsize, $gfpoly, $fcr, $prim, $nroots, $pad)

        {

            foreach(self::$items as $rs) {

                if($rs->pad != $pad)       continue;

                if($rs->nroots != $nroots) continue;

                if($rs->mm != $symsize)    continue;

                if($rs->gfpoly != $gfpoly) continue;

                if($rs->fcr != $fcr)       continue;

                if($rs->prim != $prim)     continue;



                return $rs;

            }



            $rs = QRrsItem::init_rs_char($symsize, $gfpoly, $fcr, $prim, $nroots, $pad);

            array_unshift(self::$items, $rs);



            return $rs;

        }

    }