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323 lines
6.3 KiB
323 lines
6.3 KiB
1 year ago
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<?php
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/*
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** Zabbix
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** Copyright (C) 2001-2023 Zabbix SIA
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**
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** This program is free software; you can redistribute it and/or modify
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** it under the terms of the GNU General Public License as published by
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** the Free Software Foundation; either version 2 of the License, or
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** (at your option) any later version.
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**
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** This program is distributed in the hope that it will be useful,
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** but WITHOUT ANY WARRANTY; without even the implied warranty of
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** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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** GNU General Public License for more details.
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**
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** You should have received a copy of the GNU General Public License
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** along with this program; if not, write to the Free Software
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** Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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**/
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class CConditionFormula {
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// possible parsing states
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const STATE_AFTER_OPEN_BRACE = 0;
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const STATE_AFTER_OPERATOR = 1;
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const STATE_AFTER_CLOSE_BRACE = 2;
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const STATE_AFTER_CONSTANT = 3;
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const STATE_AFTER_NOT_OPERATOR = 4;
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/**
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* Set to true of the formula is valid.
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*
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* @var bool
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*/
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public $isValid;
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/**
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* Error message if the formula is invalid.
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*
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* @var string
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*/
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public $error;
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/**
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* The parsed formula.
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*
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* @var string
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*/
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public $formula;
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/**
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* Array of unique constants used in the formula.
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*
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* @var array
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*/
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public $constants = [];
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/**
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* Array of supported operators.
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*
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* @var array
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*/
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protected $allowedOperators = ['and', 'or'];
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/**
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* Current position on a parsed element.
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*
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* @var integer
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*/
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private $pos;
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/**
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* Parses the given condition formula.
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*
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* @param string $formula
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*
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* @return bool true if the formula is valid
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*/
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public function parse($formula) {
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$this->isValid = true;
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$this->error = '';
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$this->constants = [];
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$this->pos = 0;
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$this->formula = $formula;
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$state = self::STATE_AFTER_OPEN_BRACE;
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$afterSpace = false;
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$level = 0;
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while (isset($this->formula[$this->pos])) {
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if ($this->formula[$this->pos] === ' ') {
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$afterSpace = true;
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$this->pos++;
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continue;
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}
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switch ($state) {
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case self::STATE_AFTER_OPEN_BRACE:
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switch ($this->formula[$this->pos]) {
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case '(':
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$state = self::STATE_AFTER_OPEN_BRACE;
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$level++;
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break;
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default:
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if ($this->parseConstant()) {
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$state = self::STATE_AFTER_CONSTANT;
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}
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elseif ($this->parseNotOperator()) {
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$state = self::STATE_AFTER_NOT_OPERATOR;
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}
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else {
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break 3;
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}
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}
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break;
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case self::STATE_AFTER_OPERATOR:
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switch ($this->formula[$this->pos]) {
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case '(':
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$state = self::STATE_AFTER_OPEN_BRACE;
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$level++;
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break;
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default:
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if (!$afterSpace) {
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break 3;
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}
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if ($this->parseConstant()) {
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$state = self::STATE_AFTER_CONSTANT;
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}
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elseif ($this->parseNotOperator()) {
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$state = self::STATE_AFTER_NOT_OPERATOR;
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}
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else {
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break 3;
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}
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}
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break;
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case self::STATE_AFTER_NOT_OPERATOR:
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switch ($this->formula[$this->pos]) {
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case '(':
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$state = self::STATE_AFTER_OPEN_BRACE;
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$level++;
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break;
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default:
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if (!$afterSpace) {
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break 3;
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}
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if ($this->parseConstant()) {
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$state = self::STATE_AFTER_CONSTANT;
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}
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else {
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break 3;
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}
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}
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break;
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case self::STATE_AFTER_CLOSE_BRACE:
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switch ($this->formula[$this->pos]) {
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case ')':
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if ($level == 0) {
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break 3;
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}
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$level--;
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break;
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default:
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if ($this->parseOperator()) {
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$state = self::STATE_AFTER_OPERATOR;
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}
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else {
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break 3;
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}
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}
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break;
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case self::STATE_AFTER_CONSTANT:
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switch ($this->formula[$this->pos]) {
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case ')':
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$state = self::STATE_AFTER_CLOSE_BRACE;
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if ($level == 0) {
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break 3;
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}
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$level--;
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break;
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default:
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if (!$afterSpace) {
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break 3;
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}
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if ($this->parseOperator()) {
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$state = self::STATE_AFTER_OPERATOR;
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}
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else {
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break 3;
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}
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}
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break;
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}
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$afterSpace = false;
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$this->pos++;
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}
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if ($this->pos == 0) {
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$this->error = _('expression is empty');
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$this->isValid = false;
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}
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if ($level != 0 || isset($this->formula[$this->pos]) || $state == self::STATE_AFTER_OPERATOR) {
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$this->error = _s('incorrect syntax near "%1$s"',
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substr($this->formula, $this->pos == 0 ? 0 : $this->pos - 1)
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);
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$this->isValid = false;
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}
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return $this->isValid;
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}
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/**
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* Parses a constant and advances the position to its last character.
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*
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* @return bool
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*/
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protected function parseConstant() {
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$start = $this->pos;
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while (isset($this->formula[$this->pos]) && $this->isConstantChar($this->formula[$this->pos])) {
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$this->pos++;
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}
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// empty constant
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if ($start == $this->pos) {
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return false;
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}
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$constant = substr($this->formula, $start, $this->pos - $start);
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$this->constants[] = [
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'value' => $constant,
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'pos' => $start
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];
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$this->pos--;
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return true;
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}
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/**
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* Parses a keyword and advances the position to its last character.
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*
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* @return bool
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*/
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protected function parseNotOperator() {
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if (substr($this->formula, $this->pos, 3) !== 'not') {
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return false;
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}
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$this->pos += 2;
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return true;
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}
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/**
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* Parses an operator and advances the position to its last character.
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*
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* @return bool
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*/
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protected function parseOperator() {
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$start = $this->pos;
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while (isset($this->formula[$this->pos]) && $this->isOperatorChar($this->formula[$this->pos])) {
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$this->pos++;
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}
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// empty operator
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if ($start == $this->pos) {
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return false;
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}
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$operator = substr($this->formula, $start, $this->pos - $start);
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// check if this is a valid operator
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if (!in_array($operator, $this->allowedOperators)) {
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$this->pos = $start;
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return false;
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}
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$this->pos--;
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return true;
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}
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/**
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* Returns true if the given character is a valid constant character.
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*
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* @param string $c
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*
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* @return bool
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*/
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protected function isConstantChar($c) {
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return ($c >= 'A' && $c <= 'Z');
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}
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/**
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* Returns true if the given character is a valid operator character.
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*
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* @param string $c
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*
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* @return bool
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*/
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protected function isOperatorChar($c) {
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return ($c >= 'a' && $c <= 'z');
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}
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}
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