1<?php
2/**
3 * QRrsItem.php
4 *
5 * Created by arielferrandini
6 */
7
8namespace PHPQRCode;
9
10class QRrsItem {
11
12    public $mm;                  // Bits per symbol
13    public $nn;                  // Symbols per block (= (1<<mm)-1)
14    public $alpha_to = array();  // log lookup table
15    public $index_of = array();  // Antilog lookup table
16    public $genpoly = array();   // Generator polynomial
17    public $nroots;              // Number of generator roots = number of parity symbols
18    public $fcr;                 // First consecutive root, index form
19    public $prim;                // Primitive element, index form
20    public $iprim;               // prim-th root of 1, index form
21    public $pad;                 // Padding bytes in shortened block
22    public $gfpoly;
23
24    //----------------------------------------------------------------------
25    public function modnn($x)
26    {
27        while ($x >= $this->nn) {
28            $x -= $this->nn;
29            $x = ($x >> $this->mm) + ($x & $this->nn);
30        }
31
32        return $x;
33    }
34
35    //----------------------------------------------------------------------
36    public static function init_rs_char($symsize, $gfpoly, $fcr, $prim, $nroots, $pad)
37    {
38        // Common code for intializing a Reed-Solomon control block (char or int symbols)
39        // Copyright 2004 Phil Karn, KA9Q
40        // May be used under the terms of the GNU Lesser General Public License (LGPL)
41
42        $rs = null;
43
44        // Check parameter ranges
45        if($symsize < 0 || $symsize > 8)                     return $rs;
46        if($fcr < 0 || $fcr >= (1<<$symsize))                return $rs;
47        if($prim <= 0 || $prim >= (1<<$symsize))             return $rs;
48        if($nroots < 0 || $nroots >= (1<<$symsize))          return $rs; // Can't have more roots than symbol values!
49        if($pad < 0 || $pad >= ((1<<$symsize) -1 - $nroots)) return $rs; // Too much padding
50
51        $rs = new QRrsItem();
52        $rs->mm = $symsize;
53        $rs->nn = (1<<$symsize)-1;
54        $rs->pad = $pad;
55
56        $rs->alpha_to = array_fill(0, $rs->nn+1, 0);
57        $rs->index_of = array_fill(0, $rs->nn+1, 0);
58
59        // PHP style macro replacement ;)
60        $NN =& $rs->nn;
61        $A0 =& $NN;
62
63        // Generate Galois field lookup tables
64        $rs->index_of[0] = $A0; // log(zero) = -inf
65        $rs->alpha_to[$A0] = 0; // alpha**-inf = 0
66        $sr = 1;
67
68        for($i=0; $i<$rs->nn; $i++) {
69            $rs->index_of[$sr] = $i;
70            $rs->alpha_to[$i] = $sr;
71            $sr <<= 1;
72            if($sr & (1<<$symsize)) {
73                $sr ^= $gfpoly;
74            }
75            $sr &= $rs->nn;
76        }
77
78        if($sr != 1){
79            // field generator polynomial is not primitive!
80            $rs = NULL;
81            return $rs;
82        }
83
84        /* Form RS code generator polynomial from its roots */
85        $rs->genpoly = array_fill(0, $nroots+1, 0);
86
87        $rs->fcr = $fcr;
88        $rs->prim = $prim;
89        $rs->nroots = $nroots;
90        $rs->gfpoly = $gfpoly;
91
92        /* Find prim-th root of 1, used in decoding */
93        for($iprim=1;($iprim % $prim) != 0;$iprim += $rs->nn)
94        ; // intentional empty-body loop!
95
96        $rs->iprim = (int)($iprim / $prim);
97        $rs->genpoly[0] = 1;
98
99        for ($i = 0,$root=$fcr*$prim; $i < $nroots; $i++, $root += $prim) {
100            $rs->genpoly[$i+1] = 1;
101
102            // Multiply rs->genpoly[] by  @**(root + x)
103            for ($j = $i; $j > 0; $j--) {
104                if ($rs->genpoly[$j] != 0) {
105                    $rs->genpoly[$j] = $rs->genpoly[$j-1] ^ $rs->alpha_to[$rs->modnn($rs->index_of[$rs->genpoly[$j]] + $root)];
106                } else {
107                    $rs->genpoly[$j] = $rs->genpoly[$j-1];
108                }
109            }
110            // rs->genpoly[0] can never be zero
111            $rs->genpoly[0] = $rs->alpha_to[$rs->modnn($rs->index_of[$rs->genpoly[0]] + $root)];
112        }
113
114        // convert rs->genpoly[] to index form for quicker encoding
115        for ($i = 0; $i <= $nroots; $i++)
116            $rs->genpoly[$i] = $rs->index_of[$rs->genpoly[$i]];
117
118        return $rs;
119    }
120
121    //----------------------------------------------------------------------
122    public function encode_rs_char($data, &$parity)
123    {
124        $MM       =& $this->mm;
125        $NN       =& $this->nn;
126        $ALPHA_TO =& $this->alpha_to;
127        $INDEX_OF =& $this->index_of;
128        $GENPOLY  =& $this->genpoly;
129        $NROOTS   =& $this->nroots;
130        $FCR      =& $this->fcr;
131        $PRIM     =& $this->prim;
132        $IPRIM    =& $this->iprim;
133        $PAD      =& $this->pad;
134        $A0       =& $NN;
135
136        $parity = array_fill(0, $NROOTS, 0);
137
138        for($i=0; $i< ($NN-$NROOTS-$PAD); $i++) {
139
140            $feedback = $INDEX_OF[$data[$i] ^ $parity[0]];
141            if($feedback != $A0) {
142                // feedback term is non-zero
143
144                // This line is unnecessary when GENPOLY[NROOTS] is unity, as it must
145                // always be for the polynomials constructed by init_rs()
146                $feedback = $this->modnn($NN - $GENPOLY[$NROOTS] + $feedback);
147
148                for($j=1;$j<$NROOTS;$j++) {
149                    $parity[$j] ^= $ALPHA_TO[$this->modnn($feedback + $GENPOLY[$NROOTS-$j])];
150                }
151            }
152
153            // Shift
154            array_shift($parity);
155            if($feedback != $A0) {
156                array_push($parity, $ALPHA_TO[$this->modnn($feedback + $GENPOLY[0])]);
157            } else {
158                array_push($parity, 0);
159            }
160        }
161    }
162}