1<?php
  2
  3/*
  4 * This file is part of the Symfony package.
  5 *
  6 * (c) Fabien Potencier <fabien@symfony.com>
  7 *
  8 * For the full copyright and license information, please view the LICENSE
  9 * file that was distributed with this source code.
 10 */
 11
 12namespace Symfony\Component\Yaml;
 13
 14use Symfony\Component\Yaml\Exception\ParseException;
 15
 16/**
 17 * Unescaper encapsulates unescaping rules for single and double-quoted
 18 * YAML strings.
 19 *
 20 * @author Matthew Lewinski <matthew@lewinski.org>
 21 *
 22 * @internal
 23 */
 24class Unescaper
 25{
 26    /**
 27     * Regex fragment that matches an escaped character in a double quoted string.
 28     */
 29    const REGEX_ESCAPED_CHARACTER = '\\\\(x[0-9a-fA-F]{2}|u[0-9a-fA-F]{4}|U[0-9a-fA-F]{8}|.)';
 30
 31    /**
 32     * Unescapes a single quoted string.
 33     *
 34     * @param string $value A single quoted string
 35     *
 36     * @return string The unescaped string
 37     */
 38    public function unescapeSingleQuotedString(string $value): string
 39    {
 40        return str_replace('\'\'', '\'', $value);
 41    }
 42
 43    /**
 44     * Unescapes a double quoted string.
 45     *
 46     * @param string $value A double quoted string
 47     *
 48     * @return string The unescaped string
 49     */
 50    public function unescapeDoubleQuotedString(string $value): string
 51    {
 52        $callback = function ($match) {
 53            return $this->unescapeCharacter($match[0]);
 54        };
 55
 56        // evaluate the string
 57        return preg_replace_callback('/'.self::REGEX_ESCAPED_CHARACTER.'/u', $callback, $value);
 58    }
 59
 60    /**
 61     * Unescapes a character that was found in a double-quoted string.
 62     *
 63     * @param string $value An escaped character
 64     *
 65     * @return string The unescaped character
 66     */
 67    private function unescapeCharacter(string $value): string
 68    {
 69        switch ($value[1]) {
 70            case '0':
 71                return "\x0";
 72            case 'a':
 73                return "\x7";
 74            case 'b':
 75                return "\x8";
 76            case 't':
 77                return "\t";
 78            case "\t":
 79                return "\t";
 80            case 'n':
 81                return "\n";
 82            case 'v':
 83                return "\xB";
 84            case 'f':
 85                return "\xC";
 86            case 'r':
 87                return "\r";
 88            case 'e':
 89                return "\x1B";
 90            case ' ':
 91                return ' ';
 92            case '"':
 93                return '"';
 94            case '/':
 95                return '/';
 96            case '\\':
 97                return '\\';
 98            case 'N':
 99                // U+0085 NEXT LINE
100                return "\xC2\x85";
101            case '_':
102                // U+00A0 NO-BREAK SPACE
103                return "\xC2\xA0";
104            case 'L':
105                // U+2028 LINE SEPARATOR
106                return "\xE2\x80\xA8";
107            case 'P':
108                // U+2029 PARAGRAPH SEPARATOR
109                return "\xE2\x80\xA9";
110            case 'x':
111                return self::utf8chr(hexdec(substr($value, 2, 2)));
112            case 'u':
113                return self::utf8chr(hexdec(substr($value, 2, 4)));
114            case 'U':
115                return self::utf8chr(hexdec(substr($value, 2, 8)));
116            default:
117                throw new ParseException(sprintf('Found unknown escape character "%s".', $value));
118        }
119    }
120
121    /**
122     * Get the UTF-8 character for the given code point.
123     */
124    private static function utf8chr(int $c): string
125    {
126        if (0x80 > $c %= 0x200000) {
127            return \chr($c);
128        }
129        if (0x800 > $c) {
130            return \chr(0xC0 | $c >> 6).\chr(0x80 | $c & 0x3F);
131        }
132        if (0x10000 > $c) {
133            return \chr(0xE0 | $c >> 12).\chr(0x80 | $c >> 6 & 0x3F).\chr(0x80 | $c & 0x3F);
134        }
135
136        return \chr(0xF0 | $c >> 18).\chr(0x80 | $c >> 12 & 0x3F).\chr(0x80 | $c >> 6 & 0x3F).\chr(0x80 | $c & 0x3F);
137    }
138}
139