/**
* Serialise an EasyRdf_Graph to the RDF format of choice.
*
* @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);
$ntriples = parent::serialise($graph, 'ntriples');
// Open a pipe to the rapper command
$descriptorspec = array(0 => array("pipe", "r"), 1 => array("pipe", "w"), 2 => array("pipe", "w"));
// Hack to produce more concise RDF/XML
if ($format == 'rdfxml') {
$format = 'rdfxml-abbrev';
}
$process = proc_open(escapeshellcmd($this->_rapperCmd) . " --quiet " . " --input ntriples " . " --output " . escapeshellarg($format) . " - " . 'unknown://', $descriptorspec, $pipes, '/tmp', null);
if (is_resource($process)) {
// $pipes now looks like this:
// 0 => writeable handle connected to child stdin
// 1 => readable handle connected to child stdout
// 2 => readable handle connected to child stderr
fwrite($pipes[0], $ntriples);
fclose($pipes[0]);
$output = stream_get_contents($pipes[1]);
fclose($pipes[1]);
$error = stream_get_contents($pipes[2]);
fclose($pipes[2]);
// It is important that you close any pipes before calling
// proc_close in order to avoid a deadlock
$returnValue = proc_close($process);
if ($returnValue) {
throw new EasyRdf_Exception("Failed to convert RDF: " . $error);
}
} else {
throw new EasyRdf_Exception("Failed to execute rapper command.");
}
return $output;
}
/**
* Serialise an EasyRdf_Graph to the RDF format of choice.
*
* @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);
$ntriples = parent::serialise($graph, 'ntriples');
// Hack to produce more concise RDF/XML
if ($format == 'rdfxml') {
$format = 'rdfxml-abbrev';
}
return EasyRdf_Utils::execCommandPipe($this->_rapperCmd, array('--quiet', '--input', 'ntriples', '--output', $format, '-', 'unknown://'), $ntriples);
}
/**
* Serialise an EasyRdf_Graph into an array of N-Triples objects
*
* @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);
$triples = array();
foreach ($graph->toArray() as $resource => $properties) {
foreach ($properties as $property => $values) {
foreach ($values as $value) {
array_push($triples, array('s' => $this->ntriplesResource($resource), 'p' => "<" . $this->escapeString($property) . ">", 'o' => $this->ntriplesValue($value)));
}
}
}
// Sort the triples into a consistent order
usort($triples, array($this, 'compareTriples'));
return $triples;
}
/**
* Provides a string for the given node for use in a string signature
* Non-anonymous nodes will return their string form. Grounded anonymous
* nodes will return their hashed form.
*
* @ignore
*/
private static function stringForNode($node, $hashes, $target)
{
if (is_null($node)) {
return "";
} elseif ($node['type'] == 'bnode') {
if ($node['value'] == $target) {
return "itself";
} elseif (isset($hashes[$node['value']])) {
return $hashes[$node['value']];
} else {
return "a blank node";
}
} else {
$s = new EasyRdf_Serialiser_Ntriples();
return $s->serialiseValue($node);
}
}
