153 lines
4.5 KiB
PHP
153 lines
4.5 KiB
PHP
<?php
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/**
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* This file is part of the Peast package
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*
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* (c) Marco Marchiò <marco.mm89@gmail.com>
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*
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* For the full copyright and license information refer to the LICENSE file
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* distributed with this source code
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*/
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namespace Peast\Syntax;
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/**
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* Longest Sequence Matcher. Utility class used by the scanner to consume
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* the longest sequence of character given a set of allowed characters sequences.
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*
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* @author Marco Marchiò <marco.mm89@gmail.com>
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*/
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class LSM
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{
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/**
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* Internal sequences map
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*
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* @var array
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*/
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protected $map = array();
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/**
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* Encoding handle flag
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*
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* @var bool
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*/
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protected $handleEncoding = false;
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/**
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* Class constructor
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*
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* @param array $sequences Allowed characters sequences
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* @param bool $handleEncoding True to handle encoding when matching
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*/
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function __construct($sequences, $handleEncoding = false)
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{
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$this->handleEncoding = $handleEncoding;
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foreach ($sequences as $s) {
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$this->add($s);
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}
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}
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/**
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* Adds a sequence
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*
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* @param string $sequence Sequence to add
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*
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* @return $this
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*/
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public function add($sequence)
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{
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if ($this->handleEncoding) {
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$s = Utils::stringToUTF8Array($sequence);
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$first = $s[0];
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$len = count($s);
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} else {
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$first = $sequence[0];
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$len = strlen($sequence);
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}
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if (!isset($this->map[$first])) {
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$this->map[$first] = array(
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"maxLen" => $len,
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"map" => array($sequence)
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);
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} else {
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$this->map[$first]["map"][] = $sequence;
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$this->map[$first]["maxLen"] = max($this->map[$first]["maxLen"], $len);
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}
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return $this;
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}
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/**
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* Removes a sequence
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*
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* @param string $sequence Sequence to remove
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*
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* @return $this
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*/
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public function remove($sequence)
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{
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if ($this->handleEncoding) {
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$s = Utils::stringToUTF8Array($sequence);
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$first = $s[0];
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} else {
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$first = $sequence[0];
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}
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if (isset($this->map[$first])) {
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$len = $this->handleEncoding ? count($s) : strlen($sequence);
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$this->map[$first]["map"] = array_diff(
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$this->map[$first]["map"], array($sequence)
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);
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if (!count($this->map[$first]["map"])) {
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unset($this->map[$first]);
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} elseif ($this->map[$first]["maxLen"] === $len) {
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// Recalculate the max length if necessary
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foreach ($this->map[$first]["map"] as $m) {
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$this->map[$first]["maxLen"] = max(
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$this->map[$first]["maxLen"],
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strlen($m)
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);
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}
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}
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}
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return $this;
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}
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/**
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* Executes the match. It returns an array where the first element is the
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* number of consumed characters and the second element is the match. If
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* no match is found it returns null.
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*
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* @param Scanner $scanner Scanner instance
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* @param int $index Current index
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* @param string $char Current character
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*
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* @return array|null
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*/
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public function match($scanner, $index, $char)
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{
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$consumed = 1;
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$bestMatch = null;
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if (isset($this->map[$char])) {
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//If the character is present in the map and it has a max length of
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//1, match immediately
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if ($this->map[$char]["maxLen"] === 1) {
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$bestMatch = array($consumed, $char);
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} else {
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//Otherwise consume a number of characters equal to the max
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//length and find the longest match
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$buffer = $char;
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$map = $this->map[$char]["map"];
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$maxLen = $this->map[$char]["maxLen"];
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do {
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if (in_array($buffer, $map)) {
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$bestMatch = array($consumed, $buffer);
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}
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$nextChar = $scanner->charAt($index + $consumed);
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if ($nextChar === null) {
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break;
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}
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$buffer .= $nextChar;
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$consumed++;
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} while ($consumed <= $maxLen);
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}
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}
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return $bestMatch;
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}
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} |