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31 lines
1.1 KiB
PHP
31 lines
1.1 KiB
PHP
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<?php
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/** @license MIT
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* Copyright 2017 J. King, Dustin Wilson et al.
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* See LICENSE and AUTHORS files for details */
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declare(strict_types=1);
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namespace JKingWeb\Arsse\Rule;
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abstract class Rule {
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public static function prep(string $pattern): string {
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if (preg_match_all("<`>", $pattern, $m, \PREG_OFFSET_CAPTURE)) {
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// where necessary escape our chosen delimiter (backtick) in reverse order
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foreach (array_reverse($m[0]) as [,$pos]) {
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// count the number of backslashes preceding the delimiter character
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$count = 0;
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$p = $pos;
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while ($p-- && $pattern[$p] === "\\" && ++$count);
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// if the number is even (including zero), add a backslash
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if ($count % 2 === 0) {
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$pattern = substr($pattern, 0, $pos)."\\".substr($pattern, $pos);
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}
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}
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}
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// add the delimiters and test the pattern
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$pattern = "`$pattern`u";
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if (@preg_match($pattern, "") === false) {
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throw new Exception("invalidPattern");
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}
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return $pattern;
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}
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}
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