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- <?php
- /**
- * QRrsItem.php
- *
- * Created by arielferrandini
- */
- namespace PHPQRCode;
- 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);
- }
- }
- }
- }
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