<?php

class QRrsItem
{
	public $mm;
	public $nn;
	public $alpha_to = array();
	public $index_of = array();
	public $genpoly = array();
	public $nroots;
	public $fcr;
	public $prim;
	public $iprim;
	public $pad;
	public $gfpoly;

	public function modnn($x)
	{
		while ($this->nn <= $x) {
			$x -= $this->nn;
			$x = ($x >> $this->mm) + ($x & $this->nn);
		}

		return $x;
	}

	static public function init_rs_char($symsize, $gfpoly, $fcr, $prim, $nroots, $pad)
	{
		$rs = NULL;
		if ($symsize < 0 || 8 < $symsize) {
			return $rs;
		}

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

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

		if ($nroots < 0 || 1 << $symsize <= $nroots) {
			return $rs;
		}

		if ($pad < 0 || (1 << $symsize) - 1 - $nroots <= $pad) {
			return $rs;
		}

		$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);
		$NN = &$rs->nn;
		$A0 = &$NN;
		$rs->index_of[0] = $A0;
		$rs->alpha_to[$A0] = 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) {
			$rs = NULL;
			return $rs;
		}

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

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

		$rs->iprim = (int) ($iprim / $prim);
		$rs->genpoly[0] = 1;
		$i = 0;

		for ($root = $fcr * $prim; $i < $nroots; $i++, $root += $prim) {
			$rs->genpoly[$i + 1] = 1;

			for ($j = $i; 0 < $j; $j--) {
				if ($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] = $rs->alpha_to[$rs->modnn($rs->index_of[$rs->genpoly[0]] + $root)];
		}

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

				for ($j = 1; $j < $NROOTS; $j++) {
					$parity[$j] ^= $ALPHA_TO[$this->modnn($feedback + $GENPOLY[$NROOTS - $j])];
				}
			}

			array_shift($parity);

			if ($feedback != $A0) {
				array_push($parity, $ALPHA_TO[$this->modnn($feedback + $GENPOLY[0])]);
			}
			else {
				array_push($parity, 0);
			}
		}
	}
}

class QRrs
{
	static public $items = array();

	static public 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;
	}
}


?>