<?php
/**
* @file
* Classes and functions for datastream validation.
*/
/**
* Converts a hexidecimal string to an integer.
*
* This is useful for running checks on values that appear in the binary
* of a datastream. Returns FALSE if the hex value contains non-hex characters
* or if the string would not return a 16- or 32-bit formatted big-endian
* signed integer.
*
* @param string $hex
* The hexidecimal string.
*
* @throws Exception
* if something horrible happens during the actual conversion.
*
* @return bool|int
* FALSE on failure, or the integer on success.
*/
function islandora_hex2int($hex) {
// A couple of quick string checks.
if (!ctype_xdigit($hex)) {
drupal_set_message(t('String passed to islandora_hex2int() contains non-hexidecimal characters.'), 'error');
return FALSE;
}
if (!strlen($hex) === 4 || !strlen($hex) === 8) {
drupal_set_message(t('String passed to islandora_hex2int() cannot create a 16- or 32-bit little-endian signed integer'), 'error');
return FALSE;
}
// The actual conversion.
try {
$reverse_hex = implode('', array_reverse(str_split($hex, 2)));
$int = hexdec($reverse_hex);
return $int;
}
catch (Exception $e) {
throw new Exception('An error occurred during the conversion of hexidecimal to integer.', 0, $e);
}
}
/**
* Abstraction for datastream validators.
*
* Classes extended from DatastreamValidator don't require much to be useful.
* They accept an IslandoraFedoraObject and a DSID to perform assertions on;
* all you have to do is place a series of functions inside the extended class
* using the naming convention assertThing(); each of these functions should
* ideally assert one thing and one thing only (for simplicity's sake), and
* should generate either a pass or a fail message by calling addPass() or
* addFail(). That's it, really; they don't have to return any values, as
* addPass() and addFail() just add messages to the overall pass/fail array.
*
* As long as you use those rules and naming conventions, all the magic is done
* when you instantiate the new datastream validator object.
*
* The IslandoraWebTestCase::assertDatastreams() function accepts paired DSIDs
* and datastream validator names in order to do the rest of the work. It grabs
* all the test results using getPasses() and getFails() and transforms those
* into something that DrupalWebTestCase can use.
*/
abstract class DatastreamValidator extends IslandoraTestUtilityClass {
/**
* The IslandoraFedoraObject containing the datastream to test.
*
* @var IslandoraFedoraObject|FedoraObject
*/
public $object;
/**
* The DSID of the string to test.
*
* @var string
*/
public $datastream;
/**
* The content of the datastream.
*
* @var string[]
*/
public $datastreamContent;
/**
* An array of additional required parameters.
*
* @var array
*/
public $params = array();
/**
* Constructs a DatastreamValidator.
*
* @param IslandoraFedoraObject|FedoraObject $object
* The object to grab the datastream from.
* @param string $datastream
* The DSID of the datastream itself.
* @param array $params
* An extra array of parameters the validator might need.
*/
public function __construct($object, $datastream, array $params = array()) {
$this->object = $object;
$this->datastream = $datastream;
$this->params = $params;
if ($object[$datastream]) {
$this->datastreamContent = $object[$datastream]->content;
}
else {
drupal_set_message(t("Error grabbing content from datastream %datastream in object %id", array(
'%datastream' => $datastream,
'%id' => $object->id,
)), 'error');
}
}
/**
* Helper function to run all the validators in a class.
*
* On DatastreamValidator::__construct(), this looks for any functions
* within the class beginning in "assert" and runs them. In all current cases
* (and realistically in all future cases), this adds one or more passes or
* fails to $this->passes and/or $this->fails.
*/
public function runValidators() {
if ($this->object[$this->datastream]) {
$methods = get_class_methods($this);
foreach ($methods as $method) {
if (substr($method, 0, 6) === 'assert') {
$this->$method();
}
}
}
else {
$this->addResult(FALSE, "Unable to load the requested datastream {$this->datastream} from object {$this->object->id}.");
}
}
/**
* Returns an array of IslandoraTestUtilityResults.
*
* @return IslandoraTestUtilityResult[]
* The results.
*/
public function getResults() {
if (empty($this->results)) {
$this->runValidators();
}
return $this->results;
}
/**
* Adds a result to $this->results.
*
* @param bool $type
* The type of result (TRUE for pass, FALSE for fail).
* @param string $message
* The message to put in the result.
*/
public function addResult($type, $message) {
$result = new IslandoraTestUtilityResult($type, $message, $this->getAssertionCall());
$this->results[] = $result;
}
/**
* Cycles through backtrace until the first non-assertion method is found.
*
* This is a manipulated version of DrupalWebTestCase::getAssertionCall().
* We use it here so that we can pass back assertion calls from
* DatastreamValidator assertions instead of less useful TestCase functions.
*
* @return array
* Array representing the true caller.
*/
public function getAssertionCall() {
$backtrace = debug_backtrace();
// While the current caller's function starts with 'assert', and another one
// exists after this function, keep poppin' em off.
while (substr($backtrace[1]['function'], 0, 6) !== 'assert' & & isset($backtrace[2])) {
array_shift($backtrace);
}
return _drupal_get_last_caller($backtrace);
}
}
/**
* Asserts that an object's given datastreams are common-type image files.
*
* Uses PHPGD to run the assertion check. This means that only certain kinds
* of image files can be checked. Please check the documentation for the PHPGD
* imagecreatefromstring() function to determine what filetypes are valid.
*/
class ImageDatastreamValidator extends DatastreamValidator {
/**
* Asserts the validity of an image using PHPGD.
*/
protected function assertImageGeneration() {
$assertion = imagecreatefromstring($this->datastreamContent) !== FALSE;
$pass = "Image datastream {$this->datastream} is valid.";
$fail = "Image datastream {$this->datastream} is either invalid or corrupt.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
}
/**
* Asserts the validity of any .tif/.tiff datastream.
*/
class TIFFDatastreamValidator extends DatastreamValidator {
/**
* Asserts that the TIFF contains an appropriate header.
*/
public function assertTIFFHeaderHex() {
$datastream_header_hex = self::getTIFFHeaderHex();
if ($datastream_header_hex == "49492a00") {
// In this case, the ingested TIFF is designated as using the "Intel
// byte-order" (i.e. little-endian) by starting with the characters "II"
// (repeated so that byte order does not yet need to be significant).
// The number that follows is '42' in little-endian hex, a number of
// 'deep philosophical significance' to the TIFF format creators.'
$this->addResult(TRUE, "{$this->datastream} datastream asserts that it is a valid Intel-byte-orderded TIF/TIFF file.");
}
elseif ($datastream_header_hex == "4d4d002a") {
// In this case, the ingested TIFF is designated as using the "Motorola
// byte-order" (i.e. big-endian) by starting with the characters "MM"
// instead. 42 follows once again, this time in big-endian hex.
$this->addResult(TRUE, "{$this->datastream} datastream asserts that it is a valid Motorola-byte-ordered TIF/TIFF file.");
}
else {
$this->addResult(FALSE, "{$this->datastream} datastream does not assert that it is a valid TIF/TIFF file.");
}
}
/**
* Grabs the first 8 characters from the TIFF datastream's hex.
*
* @return string
* The ... thing I just wrote up there.
*/
protected function getTIFFHeaderHex() {
return substr(bin2hex($this->datastreamContent), 0, 8);
}
}
/**
* Asserts the validity of a JP2 datastream.
*/
class JP2DatastreamValidator extends DatastreamValidator {
/**
* Asserts the hex values at the head of the JP2 file.
*
* JP2 files begin with an offset header at the second 32-bit integer,
* 0x6A502020. This header is in all .jp2s, and we check for it here.
*/
protected function assertJP2Header() {
$assertion = substr(bin2hex($this->datastreamContent), 8, 8) == '6a502020';
$pass = "Datastream {$this->datastream} contains the appropriate JP2 header.";
$fail = "Datastream {$this->datastream} does not contain the appropriate JP2 header.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
/**
* Asserts the marker at the end of the JP2 file.
*
* JP2 files have their codestream capped with a marker, 0xFFD9. We're just
* checking for it here to see if the .jp2 encoder finished okay.
*/
protected function assertJP2Marker() {
$assertion = substr(bin2hex($this->datastreamContent), strlen(bin2hex($this->datastreamContent)) - 4, 4) == 'ffd9';
$pass = "Datastream {$this->datastream} contains the appropriate JP2 ending marker.";
$fail = "Datastream {$this->datastream} does not contain the appropriate JP2 ending marker. If this is the only JP2 validator that failed, it is likely that derivative generation was interrupted.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
}
/**
* Asserts the validity of a PDF datastream.
*/
class PDFDatastreamValidator extends DatastreamValidator {
/**
* Validates the PDF signature.
*/
protected function assertPDFSignature() {
$assertion = substr($this->datastreamContent, 0, 5) == '%PDF-';
$pdf_version = substr($this->datastreamContent, 5, 3);
$pass = "{$this->datastream} datastream asserts that it is a valid PDF file using PDF version {$pdf_version}";
$fail = "{$this->datastream} datastream binary header appears to be corrupt and missing a valid PDF signature.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
/**
* Counts the number of signatures in this PDF file and asserts there are any.
*/
protected function assertPDFStreamCount() {
$pdf_stream_count = substr_count(bin2hex($this->datastreamContent), '0a73747265616d0a');
$assertion = $pdf_stream_count !== 0;
$pass = "{$this->datastream} datastream reports the existence of {$pdf_stream_count} PDF streams. Note that an extremely low number could still indicate corruption.";
$fail = "{$this->datastream} datastream contains zero PDF streams, and is likely not a PDF file.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
/**
* Validates the PDF closing tag.
*
* @return bool
* TRUE if it was present; FALSE otherwise.
*/
protected function assertPDFClosingTag() {
$assertion = strpos(bin2hex($this->datastreamContent), '0a2525454f460a') == TRUE;
$pass = "{$this->datastream} datastream reports the existence of the closing 'EOF' tag required at the end of PDFs";
$fail = "{$this->datastream} datastream does not contain the closing 'EOF' tag. If this is the only PDF validation that failed, it is likely that derivative generation was interrupted.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
}
/**
* Validates the number of times a string occurs in a datastream.
*
* Requires $this->params to be set to an array containing two keys - the first
* is the string we're looking to find in the datastream, and the second is an
* integer representing the number of times it should appear in the datastream.
*/
class TextDatastreamValidator extends DatastreamValidator {
/**
* Constructor override; blow up if we don't have our two values.
*/
public function __construct(IslandoraFedoraObject $object, $datastream, array $params = array()) {
if (count($params) < 2 ) {
throw new InvalidArgumentException('$params must contain at least two values to instantiate a TextDatastreamValidator.');
}
parent::__construct($object, $datastream, $params);
}
/**
* Asserts that the string given appears the correct number of times.
*/
protected function assertTextStringCount() {
$string_count = self::getTextStringCount();
list($string, $expected) = $this->params;
$assertion = $string_count === $expected;
$this->addResult($assertion, "{$this->datastream} datastream contains the word(s) '{$string}' repeated {$string_count} time(s) (expected: {$expected}).");
}
/**
* The number of times key [0] in $this->params appears in the datastream.
*
* @return int
* That count I just mentioned up there.
*/
protected function getTextStringCount() {
return substr_count($this->datastreamContent, $this->params[0]);
}
}
/**
* Asserts the validity a WAV datastream.
*
* WAV files contain a rigidly detailed header that contains all sorts of fun
* information we can use to validate things against other things. So, we check
* rigorously that the header contains properly constructed data by looking to
* see if certain values are at their expected byte offset. We also compare
* declared chunk sizes against actual sizes. If any of these are off, WAV
* players will fail to function.
*/
class WAVDatastreamValidator extends DatastreamValidator {
/**
* We need a special constructor here to get the hex datastream content.
*
* @param IslandoraFedoraObject $object
* The object to grab the datastream from.
* @param string $datastream
* The DSID of the datastream itself.
* @param array $params
* An extra array of parameters the validator might need.
*/
public function __construct(IslandoraFedoraObject $object, $datastream, array $params = array()) {
parent::__construct($object, $datastream, $params);
$this->datastreamContent = bin2hex($this->datastreamContent);
}
/**
* Asserts that the datastream contains a valid WAV signature.
*/
protected function assertWAVSignature() {
$signatures = str_split(substr($this->datastreamContent, 0, 24), 8);
$assertion = $signatures[0] == '52494646' & & $signatures[2] == '57415645';
$pass = "Header of the {$this->datastream} datastream contains a valid file signature.";
$fail = "Header of the {$this->datastream} datastream contains corrupt file signature.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
/**
* Asserts that the chunksize in the header is correct.
*/
protected function assertWAVChunkSize() {
$assertion = islandora_hex2int(substr($this->datastreamContent, 8, 8)) === 36 + self::getDataSubChunkSize();
$pass = "{$this->datastream} datastream chunksize in WAV header is correct";
$fail = "{$this->datastream} datastream chunksize in WAV header does not match actual chunksize.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
/**
* Asserts that the datastream contains a 'fmt' subchunk.
*/
protected function assertWAVFmtSubChunk() {
$assertion = substr($this->datastreamContent, 24, 8) === '666d7420';
$pass = "{$this->datastream} datastream contains a 'fmt' subchunk.";
$fail = "{$this->datastream} datastream is missing the required 'fmt' subchunk.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
/**
* Asserts that the byterate reported by the WAV header is valid.
*/
protected function assertWAVByteRate() {
$wav_samplerate = islandora_hex2int(substr($this->datastreamContent, 48, 8));
$assertion = islandora_hex2int(substr($this->datastreamContent, 56, 8)) === $wav_samplerate * self::getNumChannels() * self::getBytesPerSample();
$pass = "{$this->datastream} datastream byterate in the WAV header is correct.";
$fail = "{$this->datastream} datastream byterate in the WAV header does not match actual calculated byterate.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
/**
* Asserts that the block alignment is correct.
*/
protected function assertWAVBlockAlignment() {
$assertion = islandora_hex2int(substr($this->datastreamContent, 64, 4)) === self::getNumChannels() * self::getBytesPerSample();
$pass = "{$this->datastream} datastream block alignment is set correctly.";
$fail = "{$this->datastream} datastream block alignment is off.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
/**
* Asserts the existence of a 'data' subchunk.
*
* Also asserts that the subchunk size is correct.
*/
protected function assertWAVDataSubChunk() {
if (substr($this->datastreamContent, 72, 8) !== '64617461') {
$this->addResult(FALSE, "{$this->datastream} datastream is missing the 'data' subchunk.");
return;
}
else {
$this->addResult(TRUE, "{$this->datastream} datastream contains 'data' subchunk.");
$wav_numsamples = strlen(substr($this->datastreamContent, 88)) / self::getNumChannels() / self::getBytesPerSample() / 2;
$assertion = self::getDataSubChunkSize() === $wav_numsamples * self::getNumChannels() * self::getBytesPerSample();
$pass = "{$this->datastream} datastream 'data' chunk is the correct size.";
$fail = "{$this->datastream} datastream 'data' chunk is sized incorrectly.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
}
/**
* Gets the number of channels reported by the WAV header.
*
* @return int
* The number of channels reported by the datastream header.
*/
protected function getNumChannels() {
return islandora_hex2int(substr($this->datastreamContent, 44, 4));
}
/**
* Gets the reported number of byte rates per sample.
*
* @return int
* The number of bytes per sample reported by the datastream header.
*/
protected function getBytesPerSample() {
return islandora_hex2int(substr($this->datastreamContent, 68, 4)) / 8;
}
/**
* Gets the size of the 'data' subchunk.
*
* @return int
* The size of the 'data' subchunk.
*/
protected function getDataSubChunkSize() {
return islandora_hex2int(substr($this->datastreamContent, 80, 8));
}
}
/**
* Asserts the validity of any .mp3 datastream.
*
* Our default setup tries to create an MP3 using VBR, but we do some extra
* checks in case someone turns that off. If the header contains the characters
* 'Xing', it is flagged as VBR, and we can do an in-depth check on each of the
* VBR settings. Otherwise, we look for the basic MP3 signature 'fffa' or 'fffb'
* at the start of the binary.
*/
class MP3DatastreamValidator extends DatastreamValidator {
/**
* Asserts the validity of the MP3.
*
* The MP3 file format is a bit of a mess; the entire makeup of the file
* depends on whether it uses variable bit rate or static bit rate. So, I'm
* breaking my own rules here and using a single assert function so that I
* can handle the weird logic.
*/
protected function assertValidMP3() {
$this->datastreamContent = bin2hex($this->datastreamContent);
// If it's not a VBR MP3, we don't have to check much, so let's get that
// out of the way first before we go doing a bunch of potentially pointless
// math. Check to see if the VBR flag (58696e67) isn't there.
if (strpos($this->datastreamContent, '58696e67') == FALSE & & substr($this->datastreamContent, 0, 4) == 'fffa') {
$this->addResult(TRUE, "{$this->datastream} datastream is encoded as a valid MPEG-1 Layer 3 file with CRC protection");
return;
}
if (strpos($this->datastreamContent, '58696e67') == FALSE & & substr($this->datastreamContent, 0, 4) == 'fffb') {
$this->addResult(TRUE, "{$this->datastream} datastream is encoded as a valid unprotected MPEG-1 Layer 3 file");
return;
}
// And what if the flag IS set?
if (strpos($this->datastreamContent, '58696e67')) {
// Check the field flags. VBR-formatted MP3 files contain a 32-bit
// integer (stored as $mp3_flag_value) that is a combination of four
// bits, each one indicating the on-off status of a VBR setting, via
// logical OR. Rather than disassembling this value into individual
// bits, we use the algorithm "if (binary_total+bit_value*2)/bit_value*2
// is greater than or equal to bit_value, that bit is turned on" to find
// the status of each bit, so we know whether to offset the rest.
$mp3_field_offset = array(0, 0, 0);
$mp3_vbrheader = substr($this->datastreamContent, strpos($this->datastreamContent, '58696e67'), 240);
$mp3_flag_value = hexdec(substr($mp3_vbrheader, 8, 8));
// We can't use the first flag, but we still need to offset the rest.
if (($mp3_flag_value + 1) % 2 == 0) {
$mp3_field_offset[0] += 8;
$mp3_field_offset[1] += 8;
$mp3_field_offset[2] += 8;
}
// The second flag leads us to filesize data, which we can verify.
if (($mp3_flag_value + 4) % 4 > 1) {
$mp3_field_bytes = hexdec(substr($mp3_vbrheader, $mp3_field_offset[0] + 16, 8));
$mp3_size = strlen($this->datastreamContent) / 2;
$assertion = $mp3_size == $mp3_field_bytes;
$pass = "{$this->datastream} datastream reported filesize of {$mp3_size} bytes matches size field value of {$mp3_field_bytes}";
$fail = "{$this->datastream} datastream reported filesize of {$mp3_size} bytes does not match size field value of {$mp3_field_bytes}";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
$mp3_field_offset[1] += 8;
$mp3_field_offset[2] += 8;
}
// We can't use the third flag for anything, but we still have to offset.
if (($mp3_flag_value + 8) % 8 > 3) {
$mp3_field_offset[2] += 200;
}
// The fourth flag leads us to VBR quality data, which we can validate.
if ($mp3_flag_value > 7) {
$mp3_field_quality = hexdec(substr($mp3_vbrheader, $mp3_field_offset[2] + 16, 8));
$assertion = $mp3_field_quality < = 100 & & $mp3_field_quality >= 0;
$pass = "{$this->datastream} datastream reports valid VBR quality of {$mp3_field_quality} (expected: between 0-100)";
$fail = "{$this->datastream} datastream reports invalid VBR quality of {$mp3_field_quality} (expected: between 0-100)";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
}
// If none of that works out, fail.
else {
$this->addResult(FALSE, "{$this->datastream} datastream is corrupt and does not identify as a valid MP3.");
}
}
}
/**
* Attempts to validate an .mp4 datastream.
*
* MP4 files are a subset of the ISO file format specification, and as such need
* to contain a 64-bit declaration of type within the first eight eight bytes of
* the file. This declaration is comprised of the characters 'ftyp', followed by
* a four-character filetype code. Here, we look for 'ftyp', and then pass the
* filetype code to the test message.
*/
class MP4DatastreamValidator extends DatastreamValidator {
/**
* Asserts that the datastream is ISO-formatted video.
*/
protected function assertISOVideo() {
$mp4_ftyp = substr(strpos($this->datastreamContent, 'ftyp'), 4, 4);
$assertion = strpos($this->datastreamContent, 'ftyp') !== 0;
$pass = "{$this->datastream} datastream asserts that it is a valid ISO-formatted video file using ftyp {$mp4_ftyp}";
$fail = "{$this->datastream} datastream is not a valid ISO-formatted video";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
}
/**
* Attempts to validate an .ogg/ogv datastream using Vorbis and Theora encoding.
*
* OGG files are made up of several 'pages' of OGG data, each prefaced with an
* OGG marker - the letters 'OggS'. The file header also contains information on
* what encoders were used to create the file. Here, we're looking for at least
* one OGG page, and confirming that the file asserts the Theora and Vorbis
* codecs were used to create the file.
*/
class OGGDatastreamValidator extends DatastreamValidator {
/**
* Asserts that the datastream contains ogg pages.
*/
protected function assertOGGPages() {
$ogg_pages = substr_count($this->datastreamContent, 'OggS');
$assertion = $ogg_pages !== 0;
$pass = "{$this->datastream} datastream asserts that it contains {$ogg_pages} Ogg pages (even a very small file should contain several).";
$fail = "{$this->datastream} datastream contains no Ogg pages.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
/**
* Asserts that the datastream contains Theora-encoded video.
*/
protected function assertTheoraVideo() {
$assertion = substr_count($this->datastreamContent, 'theora') !== 0;
$pass = "{$this->datastream} datastream asserts that it contains Theora-encoded video data.";
$fail = "{$this->datastream} datastream contains no marker indicating the presence of Theora-encoded video data.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
/**
* Asserts that the datastream contains Vorbis-encoded audio.
*/
protected function assertVorbisAudio() {
$assertion = substr_count($this->datastreamContent, 'vorbis') !== 0;
$pass = "{$this->datastream} datastream asserts that it contains Vorbis-encoded audio data";
$fail = "{$this->datastream} datastream contains no marker indicating the presence of Vorbis-encoded audio data.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
}
/**
* Attempts to validate an .mkv datastream.
*
* There's not much we can do to check an MKV file, since the format is really,
* really loose. We do know a couple of things though - first, since MKV is an
* EBML format, the first four characters will always be the same. Since they're
* non-standard characters, we're looking at their hex values instead. And
* second, we know that the file will contain the declaration 'matroska' soon
* after.
*/
class MKVDatastreamValidator extends DatastreamValidator {
/**
* Asserts that the datastream is an EBML-format file.
*/
protected function assertEBMLFormat() {
$assertion = substr(bin2hex($this->datastreamContent), 0, 8) == '1a45dfa3';
$pass = "{$this->datastream} datastream asserts that it is an EBML-formatted file";
$fail = "{$this->datastream} datastream is not an EBML-formatted file.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
/**
* Asserts that the datastream contains a matroska marker.
*/
protected function assertMatroskaMarker() {
$assertion = substr_count($this->datastreamContent, 'matroska') == 1;
$pass = "{$this->datastream} datastream asserts that its EBML DocType is Matroska";
$fail = "{$this->datastream} datastream does not contain a Matroska EBML DocType marker.";
$message = $assertion ? $pass : $fail;
$this->addResult($assertion, $message);
}
}
