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