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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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