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   1  <?php
   2  
   3  namespace Algo26\IdnaConvert\Punycode;
   4  
   5  class FromPunycode extends AbstractPunycode implements PunycodeInterface
   6  {
   7      public function __construct(?string $idnVersion = null)
   8      {
   9          parent::__construct();
  10      }
  11  
  12      /**
  13       * The actual decoding algorithm
  14       * @param string
  15       * @return mixed
  16       */
  17      public function convert($encoded)
  18      {
  19          if (!$this->validate($encoded)) {
  20              return false;
  21          }
  22  
  23          $decoded = [];
  24          // Find last occurrence of the delimiter
  25          $delimiterPosition = strrpos($encoded, '-');
  26          if ($delimiterPosition > self::byteLength(self::punycodePrefix)) {
  27              for ($k = $this->byteLength(self::punycodePrefix); $k < $delimiterPosition; ++$k) {
  28                  $decoded[] = ord($encoded[$k]);
  29              }
  30          }
  31          $decodedLength = count($decoded);
  32          $encodedLength = $this->byteLength($encoded);
  33  
  34          // Wandering through the strings; init
  35          $isFirst = true;
  36          $bias = self::initialBias;
  37          $currentIndex = 0;
  38          $char = self::initialN;
  39  
  40          for ($encodedIndex = ($delimiterPosition) ? ($delimiterPosition + 1) : 0; $encodedIndex < $encodedLength; ++$decodedLength) {
  41              for ($oldIndex = $currentIndex, $w = 1, $k = self::base; 1; $k += self::base) {
  42                  $digit = $this->decodeDigit($encoded[$encodedIndex++]);
  43                  $currentIndex += $digit * $w;
  44                  $t = ($k <= $bias)
  45                      ? self::tMin
  46                      : (
  47                          ($k >= $bias + self::tMax)
  48                              ? self::tMax
  49                              : ($k - $bias)
  50                      );
  51                  if ($digit < $t) {
  52                      break;
  53                  }
  54                  $w = (int) ($w * (self::base - $t));
  55              }
  56              $bias = $this->adapt($currentIndex - $oldIndex, $decodedLength + 1, $isFirst);
  57              $isFirst = false;
  58              $char += (int) ($currentIndex / ($decodedLength + 1));
  59              $currentIndex %= ($decodedLength + 1);
  60              if ($decodedLength > 0) {
  61                  // Make room for the decoded char
  62                  for ($i = $decodedLength; $i > $currentIndex; $i--) {
  63                      $decoded[$i] = $decoded[($i - 1)];
  64                  }
  65              }
  66              $decoded[$currentIndex++] = $char;
  67          }
  68  
  69          return $this->unicodeTransCoder->convert(
  70              $decoded,
  71              $this->unicodeTransCoder::FORMAT_UCS4_ARRAY,
  72              $this->unicodeTransCoder::FORMAT_UTF8
  73          );
  74      }
  75  
  76  
  77      /**
  78       * Checks, whether or not the provided string is a valid punycode string
  79       * @param string $encoded
  80       * @return boolean
  81       */
  82      private function validate($encoded): bool
  83      {
  84          // Check for existence of the prefix
  85          if (strpos($encoded, self::punycodePrefix) !== 0) {
  86              return false;
  87          }
  88  
  89          // If nothing is left after the prefix, it is hopeless
  90          if (strlen(trim($encoded)) <= strlen(self::punycodePrefix)) {
  91              return false;
  92          }
  93  
  94          return true;
  95      }
  96  
  97      private function decodeDigit(string $cp): int
  98      {
  99          $cp = ord($cp);
 100          if ($cp - 48 < 10) {
 101              return $cp - 22;
 102          }
 103  
 104          if ($cp - 65 < 26) {
 105              return $cp - 65;
 106          }
 107  
 108          if ($cp - 97 < 26) {
 109              return $cp - 97;
 110          }
 111  
 112          return self::base;
 113      }
 114  }