class EasyRdf_Serialiser_Ntriples

Format.php in drupal/core/vendor/easyrdf/easyrdf/lib/EasyRdf/Format.php

class EasyRdf_Serialiser_Ntriples extends EasyRdf_Serialiser {
  private $escChars = array();

  // Character encoding cache

  /**
   * @ignore
   */
  protected function escapeString($str) {
    if (strpos(utf8_decode(str_replace('?', '', $str)), '?') === false) {
      $str = utf8_decode($str);
    }
    $result = '';
    $strLen = strlen($str);
    for ($i = 0; $i < $strLen; $i++) {
      $c = $str[$i];
      if (!isset($this->escChars[$c])) {
        $this->escChars[$c] = $this
          ->escapedChar($c);
      }
      $result .= $this->escChars[$c];
    }
    return $result;
  }

  /**
   * @ignore
   */
  protected function unicodeCharNo($c) {
    $cUtf = utf8_encode($c);
    $bl = strlen($cUtf);

    /* binary length */
    $r = 0;
    switch ($bl) {
      case 1:

        /* 0####### (0-127) */
        $r = ord($cUtf);
        break;
      case 2:

        /* 110##### 10###### = 192+x 128+x */
        $r = (ord($cUtf[0]) - 192) * 64 + (ord($cUtf[1]) - 128);
        break;
      case 3:

        /* 1110#### 10###### 10###### = 224+x 128+x 128+x */
        $r = (ord($cUtf[0]) - 224) * 4096 + (ord($cUtf[1]) - 128) * 64 + (ord($cUtf[2]) - 128);
        break;
      case 4:

        /* 1111#### 10###### 10###### 10###### = 240+x 128+x 128+x 128+x */
        $r = (ord($cUtf[0]) - 240) * 262144 + (ord($cUtf[1]) - 128) * 4096 + (ord($cUtf[2]) - 128) * 64 + (ord($cUtf[3]) - 128);
        break;
    }
    return $r;
  }

  /**
   * @ignore
   */
  protected function escapedChar($c) {
    $no = $this
      ->unicodeCharNo($c);

    /* see http://www.w3.org/TR/rdf-testcases/#ntrip_strings */
    if ($no < 9) {
      return "\\u" . sprintf('%04X', $no);

      /* #x0-#x8 (0-8) */
    }
    elseif ($no == 9) {
      return '\\t';

      /* #x9 (9) */
    }
    elseif ($no == 10) {
      return '\\n';

      /* #xA (10) */
    }
    elseif ($no < 13) {
      return "\\u" . sprintf('%04X', $no);

      /* #xB-#xC (11-12) */
    }
    elseif ($no == 13) {
      return '\\r';

      /* #xD (13) */
    }
    elseif ($no < 32) {
      return "\\u" . sprintf('%04X', $no);

      /* #xE-#x1F (14-31) */
    }
    elseif ($no < 34) {
      return $c;

      /* #x20-#x21 (32-33) */
    }
    elseif ($no == 34) {
      return '\\"';

      /* #x22 (34) */
    }
    elseif ($no < 92) {
      return $c;

      /* #x23-#x5B (35-91) */
    }
    elseif ($no == 92) {
      return '\\';

      /* #x5C (92) */
    }
    elseif ($no < 127) {
      return $c;

      /* #x5D-#x7E (93-126) */
    }
    elseif ($no < 65536) {
      return "\\u" . sprintf('%04X', $no);

      /* #x7F-#xFFFF (128-65535) */
    }
    elseif ($no < 1114112) {
      return "\\U" . sprintf('%08X', $no);

      /* #x10000-#x10FFFF (65536-1114111) */
    }
    else {
      return '';

      /* not defined => ignore */
    }
  }

  /**
   * @ignore
   */
  protected function ntriplesResource($res) {
    $escaped = $this
      ->escapeString($res);
    if (substr($res, 0, 2) == '_:') {
      return $escaped;
    }
    else {
      return "<{$escaped}>";
    }
  }

  /**
   * @ignore
   */
  protected function ntriplesValue($value) {
    if ($value['type'] == 'uri' or $value['type'] == 'bnode') {
      return $this
        ->ntriplesResource($value['value']);
    }
    elseif ($value['type'] == 'literal') {
      $escaped = $this
        ->escapeString($value['value']);
      if (isset($value['lang'])) {
        $lang = $this
          ->escapeString($value['lang']);
        return '"' . $escaped . '"' . '@' . $lang;
      }
      elseif (isset($value['datatype'])) {
        $datatype = $this
          ->escapeString($value['datatype']);
        return '"' . $escaped . '"' . "^^<{$datatype}>";
      }
      else {
        return '"' . $escaped . '"';
      }
    }
    else {
      throw new EasyRdf_Exception("Unable to serialise object to ntriples: " . $value['type']);
    }
  }

  /**
   * Serialise an EasyRdf_Graph into N-Triples
   *
   * @param object EasyRdf_Graph $graph   An EasyRdf_Graph object.
   * @param string  $format               The name of the format to convert to.
   * @return string                       The RDF in the new desired format.
   */
  public function serialise($graph, $format) {
    parent::checkSerialiseParams($graph, $format);
    if ($format == 'ntriples') {
      $nt = '';
      foreach ($graph
        ->toArray() as $resource => $properties) {
        foreach ($properties as $property => $values) {
          foreach ($values as $value) {
            $nt .= $this
              ->ntriplesResource($resource) . " ";
            $nt .= "<" . $this
              ->escapeString($property) . "> ";
            $nt .= $this
              ->ntriplesValue($value) . " .\n";
          }
        }
      }
      return $nt;
    }
    else {
      throw new EasyRdf_Exception("EasyRdf_Serialiser_Ntriples does not support: {$format}");
    }
  }

}