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<?php |
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/** |
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* @file |
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* Assertions for various datastream types. |
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* |
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* For a datastream validator to work correctly with IslandoraWebTestCase:: |
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* validateDatastreams(), it needs to return an array of results, each entry of |
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* which contains two values: first, TRUE or FALSE, depending on whether or not |
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* that particular result passed or failed, and second, a string containing a |
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* message to accompany the result. |
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* |
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* It also should contain three parameters, all of which may use any label, but |
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* must be organized in the following order: |
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* $object - an object that the datastream can be loaded from. |
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* $datastream - a DSID to pull from $object. |
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* $optional_params - a parameter for any data the function requires. |
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* |
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* When IslandoraWebTestCase::validateDatastreams() is called, it is passed an |
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* array of datastreams, each of which is itself an array containing the DSID of |
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* the datastream, the middle of the function name (image, pdf, tiff, etc.), and |
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* (optional) data to be passed to that third parameter. |
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*/ |
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/** |
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* A function to pass assertions to and receive results from. |
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* |
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* @param bool $assertion |
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* The if/then statement to validate against. |
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* @param array $results |
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* An array of results to append the generated result to. |
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* @param string $pass |
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* A message to return if the assertion turns up true. |
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* @param string $fail |
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* An optional message to return if the assertion turns up false. |
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* If left empty, the $pass message will be returned. |
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* |
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* @return array |
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* A result that can be made useful in the validation functions below. |
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*/ |
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function islandora_assert_valid($assertion, $results, $pass, $fail = NULL) { |
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if ($assertion) { |
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$result = array(TRUE, $pass); |
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} |
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else { |
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if (isset($fail)) { |
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$result = array(FALSE, $fail); |
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} |
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else { |
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$result = array(FALSE, $pass); |
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} |
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} |
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array_push($results, $result); |
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return $results; |
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} |
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/** |
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* Converts a hexidecimal string to an integer. |
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* |
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* This is useful for running checks on values that appear in the binary |
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* of a datastream. Returns FALSE if the hex value contains non-hex characters |
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* or if the string would not return a 16- or 32-bit formatted big-endian |
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* signed integer. |
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* |
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* @param string $hex |
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* The hexidecimal string. |
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* |
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* @return bool|int |
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* FALSE on failure, or the integer on success. |
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*/ |
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function islandora_hex2int($hex) { |
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// A couple of quick string checks. |
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if (!ctype_xdigit($hex)) { |
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drupal_set_message(t('String passed to islandora_hex2int() contains non-hexidecimal characters.'), 'error'); |
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return FALSE; |
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} |
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if (!strlen($hex) === 4 || !strlen($hex) === 8) { |
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drupal_set_message(t('String passed to islandora_hex2int() cannot create a 16- or 32-bit little-endian signed integer'), 'error'); |
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return FALSE; |
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} |
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// The actual conversion. |
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try { |
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$reverse_hex = implode('', array_reverse(str_split($hex, 2))); |
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$int = hexdec($reverse_hex); |
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return $int; |
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} |
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catch (Exception $e) { |
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throw new Exception('An error occurred during the conversion of hexidecimal to integer.', 0, $e); |
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} |
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} |
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/** |
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* Asserts that an object's given datastreams are common-type image files. |
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* |
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* Uses PHPGD to run the assertion check. This means that only certain kinds |
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* of image files can be checked. Please check the documentation for the PHPGD |
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* imagecreatefromstring() function to determine what filetypes are valid. |
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* |
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* @param AbstractObject $object |
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* The PID of the object. |
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* @param string $datastream |
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* A DSID to check that corresponds to a PHPGD-valid image datastream. |
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* |
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* @return array |
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* A series of TRUE(pass)/FALSE(fail) results paired with result messages. |
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*/ |
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function islandora_validate_image_datastream($object, $datastream) { |
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$datastream_string = $object[$datastream]->content; |
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$results = array(); |
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$pass = "Image datastream {$datastream} is valid."; |
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$fail = "Image datastream {$datastream} is either invalid or corrupt."; |
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$results = islandora_assert_valid(imagecreatefromstring($datastream_string), $results, $pass, $fail); |
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return $results; |
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} |
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/** |
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* Asserts the validity of any .tif/.tiff datastream. |
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* |
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* Does not use the islandora_assert_valid() function, as this is not a simple |
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* true/false. |
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* |
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* @param AbstractObject $object |
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* The PID of the object. |
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* @param string $datastream |
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* A DSID to check that corresponds to a .tif/.tiff datastream. |
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* |
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* @return array |
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* A series of TRUE(pass)/FALSE(fail) results paired with result messages. |
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*/ |
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function islandora_validate_tiff_datastream($object, $datastream) { |
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$datastream_string = $object[$datastream]->content; |
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$datastream_header_hex = substr(bin2hex($datastream_string), 0, 8); |
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$results = array(); |
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if ($datastream_header_hex == "49492a00") { |
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// In this case, the ingested TIFF is designated as using the "Intel |
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// byte-order" (e.g. little-endian) by starting with the characters "II" |
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// (repeated so that byte order does not yet need to be significant). |
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// The number that follows is '42' in little-endian hex, a number of |
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// 'deep philosophical significance' to the TIFF format creators. |
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array_push($results, array(TRUE, "{$datastream} datastream asserts that it is a valid Intel-byte-orderded TIF/TIFF file.")); |
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} |
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elseif ($datastream_header_hex == "4d4d002a") { |
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// In this case, the ingested TIFF is designated as using the "Motorola |
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// byte-order" (e.g. big-endian) by starting with the characters "MM" |
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// instead. 42 follows once again, this time in big-endian hex. |
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array_push($results, array(TRUE, "{$datastream} datastream asserts that it is a valid Motorola-byte-ordered TIF/TIFF file.")); |
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} |
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else { |
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array_push($results, array(FALSE, "{$datastream} datastream does not assert that it is a valid TIF/TIFF file.")); |
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} |
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return $results; |
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} |
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/** |
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* Asserts the validity of any .jp2 datastream. |
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* |
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* @param AbstractObject $object |
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* The PID of the object. |
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* @param string $datastream |
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* A DSID to check that corresponds to a .jp2 datastream. |
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* |
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* @return array |
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* A series of TRUE(pass)/FALSE(fail) results paired with result messages. |
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*/ |
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function islandora_validate_jp2_datastream($object, $datastream) { |
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$datastream_hex = bin2hex($object[$datastream]->content); |
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$results = array(); |
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// JP2 files begin with an offset header at the second 32-bit integer, |
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// 0x6A502020. This header is in all .jp2s, and we check for it here. |
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$pass = "{$datastream} datastream begins correctly with the appropriate .jp2 header."; |
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$fail = "{$datastream} datastream does not begin with the appropriate .jp2 header."; |
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$results = islandora_assert_valid(substr($datastream_hex, 8, 8) == '6a502020', $results, $pass, $fail); |
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// JP2 files have their codestream capped with a marker, 0xFFD9. We're |
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// just checking for it here to see if the .jp2 encoder finished okay. |
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$pass = "{$datastream} datastream ends correctly with the appropriate .jp2 marker."; |
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$fail = "{$datastream} datastream does not end with a .jp2 marker; derivative generation was likely interrupted."; |
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$results = islandora_assert_valid(substr($datastream_hex, strlen($datastream_hex) - 4, 4) == 'ffd9', $results, $pass, $fail); |
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return $results; |
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} |
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/** |
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* Asserts the validity of any .pdf datastream. |
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* |
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* @param AbstractObject $object |
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* The PID of the object. |
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* @param string $datastream |
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* A DSID to check that corresponds to a .pdf datastream. |
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* |
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* @return array |
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* A series of TRUE(pass)/FALSE(fail) results paired with result messages. |
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*/ |
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function islandora_validate_pdf_datastream($object, $datastream) { |
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$pdf = $object[$datastream]->content; |
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$pdf_version = substr($pdf, 5, 3); |
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$results = array(); |
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$pass = "{$datastream} datastream asserts that it is a valid PDF file using PDF version {$pdf_version}"; |
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$fail = "{$datastream} datastream binary header appears to be corrupt and missing a valid PDF signature."; |
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$results = islandora_assert_valid(substr($pdf, 0, 5) == '%PDF-', $results, $pass, $fail); |
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$pdf_streams = substr_count(bin2hex($pdf), '0a73747265616d0a'); |
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$pass = "{$datastream} datastream reports the existence of {$pdf_streams} PDF streams. Note that an extremely low number could still indicate corruption."; |
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$fail = "{$datastream} datastream contains zero PDF streams, and is likely not a PDF file."; |
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$results = islandora_assert_valid($pdf_streams, $results, $pass, $fail); |
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$pass = "{$datastream} datastream reports the existence of the closing 'EOF' tag required at the end of PDFs"; |
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$fail = "{$datastream} datastream does not contain the closing 'EOF' tag. If this is the only PDF validation that failed, it is likely that derivative generation was interrupted."; |
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$results = islandora_assert_valid(strpos(bin2hex($pdf), '0a2525454f460a'), $results, $pass, $fail); |
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return $results; |
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} |
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/** |
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* Asserts that a string of text shows up inside a datastream. |
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* |
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* @param AbstractObject $object |
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* The PID of the object. |
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* @param string $datastream |
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* A DSID to check that corresponds to a datastream containing text. |
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* @param array $text |
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* An array of strings/the number of times it should appear in the datastream. |
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* |
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* @return array |
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* A series of TRUE(pass)/FALSE(fail) results paired with result messages. |
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*/ |
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function islandora_validate_text_datastream($object, $datastream, array $text) { |
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$results = array(); |
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$content = $object[$datastream]->content; |
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$string_count = substr_count($content, $text[0]); |
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$pass = "{$datastream} datastream contains the word(s) '{$text[0]}' repeated {$string_count} time(s) (expected: {$text[1]})."; |
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$fail = "{$datastream} datastream contains the word(s) '{$text[0]}' repeated {$string_count} time(s) (expected: {$text[1]})."; |
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$results = islandora_assert_valid($string_count == $text[1], $results, $pass, $fail); |
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return $results; |
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} |
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/** |
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* Asserts the validity of any .wav datastraeam. |
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* |
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* WAV files contain a rigidly detailed header that contains all sorts of fun |
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* information we can use to validate things against other things. So, we check |
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* rigorously that the header contains properly constructed data by looking to |
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* see if certain values are at their expected byte offset. We also compare |
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* declared chunk sizes against actual sizes. If any of these are off, WAV |
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* players will fail to function. |
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* |
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* @param AbstractObject $object |
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* The PID of the object. |
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* @param string $datastream |
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* A DSID to check that corresponds to a datastream generated via OCR or HOCR. |
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* |
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* @return array |
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* A series of TRUE(pass)/FALSE(fail) results paired with result messages. |
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*/ |
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function islandora_validate_wav_datastream($object, $datastream) { |
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$results = array(); |
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$wav = bin2hex($object['OBJ']->content); |
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$wav_subchunk2size = islandora_hex2int(substr($wav, 80, 8)); |
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$wav_samplerate = islandora_hex2int(substr($wav, 48, 8)); |
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$wav_numchannels = islandora_hex2int(substr($wav, 44, 4)); |
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$wav_bytespersample = islandora_hex2int(substr($wav, 68, 4)) / 8; |
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$wav_numsamples = strlen(substr($wav, 88)) / $wav_numchannels / $wav_bytespersample / 2; |
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$magic_number = str_split(substr($wav, 0, 24), 8); |
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$pass = "Header of the {$datastream} datastream contains correct file signature"; |
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$fail = "Header of the {$datastream} datastream contains corrupt file signature"; |
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$results = islandora_assert_valid($magic_number[0] = '52494646' && $magic_number[2] = '57415645', $results, $pass, $fail); |
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$pass = "{$datastream} datastream chunksize in WAV header is correct"; |
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$fail = "{$datastream} datastream chunksize in WAV header does not match actual chunksize."; |
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$results = islandora_assert_valid(islandora_hex2int(substr($wav, 8, 8)) === 36 + $wav_subchunk2size, $results, $pass, $fail); |
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$pass = "{$datastream} datastream contains a 'fmt' subchunk."; |
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$fail = "{$datastream} datastream is missing the required 'fmt' subchunk."; |
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$results = islandora_assert_valid(substr($wav, 24, 8) === '666d7420', $results, $pass, $fail); |
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$pass = "{$datastream} datastream byterate in the WAV header is correct."; |
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$fail = "{$datastream} datastream byterate in the WAV header does not match actual calculated byterate."; |
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$results = islandora_assert_valid(islandora_hex2int(substr($wav, 56, 8)) === $wav_samplerate * $wav_numchannels * $wav_bytespersample, $results, $pass, $fail); |
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$pass = "{$datastream} datastream block alignment is set correctly."; |
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$fail = "{$datastream} datastream block alignment is off."; |
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$results = islandora_assert_valid(islandora_hex2int(substr($wav, 64, 4)) === $wav_numchannels * $wav_bytespersample, $results, $pass, $fail); |
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$pass = "{$datastream} datastream contains 'data' subchunk."; |
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$fail = "{$datastream} datastream is missing the 'data' subchunk."; |
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$results = islandora_assert_valid(substr($wav, 72, 8) === '64617461', $results, $pass, $fail); |
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$pass = "{$datastream} datastream 'data' chunk is the correct size."; |
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$fail = "{$datastream} datastream 'data' chunk is sized incorrectly."; |
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$results = islandora_assert_valid($wav_subchunk2size === $wav_numsamples * $wav_numchannels * $wav_bytespersample, $results, $pass, $fail); |
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return $results; |
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} |
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/** |
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* Asserts the validity of any .mp3 datastream. |
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* |
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* Our default setup tries to create an MP3 using VBR, but we do some extra |
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* checks in case someone turns that off. If the header contains the characters |
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* 'Xing', it is flagged as VBR, and we can do an in-depth check on each of the |
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* VBR settings. Otherwise, we look for the basic MP3 signature 'fffa' or 'fffb' |
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* at the start of the binary. |
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* |
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* @param AbstractObject $object |
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* The PID of the object. |
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* @param string $datastream |
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* A DSID of a datastream corresponding to an mp3 file. |
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* |
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* @return array |
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* A series of TRUE(pass)/FALSE(fail) results paired with result messages. |
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*/ |
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function islandora_validate_mp3_datastream($object, $datastream) { |
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$results = array(); |
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$mp3 = bin2hex($object[$datastream]->content); |
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$mp3_size = strlen($mp3) / 2; |
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// Looks to see if VBR was set properly by LAME. If so, MATH TIME! |
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if (strpos($mp3, '58696e67')) { |
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$mp3_vbrheader = substr($mp3, strpos($mp3, '58696e67'), 240); |
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// Check the field flags. VBR-formatted MP3 files contain a 32-bit |
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// integer (stored as $mp3_flag_value) that is a combination of four |
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// bits, each one indicating the on-off status of a VBR setting, via |
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// logical OR. Rather than disassembling this value into individual |
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// bits, we use the algorithm "if (binary_total+bit_value*2)/bit_value*2 |
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// is greater than or equal to bit_value, that bit is turned on" to find |
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// the status of each bit, so we know whether to offset the rest. |
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$mp3_field_offset = array(0, 0, 0); |
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$mp3_flag_value = hexdec(substr($mp3_vbrheader, 8, 8)); |
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// We can't use the first flag, but we still need to offset the rest. |
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if (($mp3_flag_value + 1) % 2 == 0) { |
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$mp3_field_offset[0] += 8; |
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$mp3_field_offset[1] += 8; |
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$mp3_field_offset[2] += 8; |
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} |
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// The second flag leads us to filesize data, which we can verify. |
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if (($mp3_flag_value + 4) % 4 > 1) { |
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$mp3_field_bytes = hexdec(substr($mp3_vbrheader, $mp3_field_offset[0] + 16, 8)); |
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$pass = "{$datastream} datastream reported filesize of {$mp3_size} bytes matches size field value of {$mp3_field_bytes}"; |
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$fail = "{$datastream} datastream reported filesize of {$mp3_size} bytes does not match size field value of {$mp3_field_bytes}"; |
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$results = islandora_assert_valid($mp3_size == $mp3_field_bytes, $results, $pass, $fail); |
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$mp3_field_offset[1] += 8; |
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$mp3_field_offset[2] += 8; |
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} |
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// We can't use the third flag for anything either. |
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if (($mp3_flag_value + 8) % 8 > 3) { |
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$mp3_field_offset[2] += 200; |
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} |
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// The fourth flag leads us to VBR quality data, which we can validate. |
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if ($mp3_flag_value > 7) { |
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$mp3_field_quality = hexdec(substr($mp3_vbrheader, $mp3_field_offset[2] + 16, 8)); |
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$pass = "{$datastream} datastream reports valid VBR quality of {$mp3_field_quality} (expected: between 0-100)"; |
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$fail = "{$datastream} datastream reports invalid VBR quality of {$mp3_field_quality} (expected: between 0-100)"; |
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$results = islandora_assert_valid($mp3_field_quality <= 100 && $mp3_field_quality >= 0, $results, $pass, $fail); |
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} |
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} |
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// Otherwise, just forget everything and check the file signature. |
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elseif (strpos($mp3, '58696e67') == FALSE && substr($mp3, 0, 4) == 'fffa') { |
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$results = array(array(TRUE, "{$datastream} datastream is encoded as a valid MPEG-1 Layer 3 file with CRC protection")); |
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} |
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elseif (strpos($mp3, '58696e67') == FALSE && substr($mp3, 0, 4) == 'fffb') { |
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$results = array(array(TRUE, "{$datastream} datastream is encoded as a valid unprotected MPEG-1 Layer 3 file")); |
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} |
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else { |
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$results = array(array(FALSE, "{$datastream} datastream is corrupt and does not identify as a valid MP3.")); |
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} |
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return $results; |
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} |
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/** |
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* Attempts to validate an .mp4 datastream. |
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* |
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* MP4 files are a subset of the ISO file format specification, and as such need |
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* to contain a 64-bit declaration of type within the first eight eight bytes of |
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* the file. This declaration is comprised of the characters 'ftyp', followed by |
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* a four-character filetype code. Below, we look for 'ftyp', and then pass the |
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* filetype code to the test message. |
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* |
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* @param AbstractObject $object |
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* The PID of the object. |
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* @param string $datastream |
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* A DSID of a datastream corresponding to an mp4 file. |
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* |
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* @return array |
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* A series of TRUE(pass)/FALSE(fail) results paired with result messages. |
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*/ |
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function islandora_validate_mp4_datastream($object, $datastream) { |
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$results = array(); |
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$mp4 = $object[$datastream]->content; |
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if (strpos($mp4, 'ftyp')) { |
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$mp4_ftyp = substr(strpos($mp4, 'ftyp'), 4, 4); |
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} |
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$pass = "{$datastream} datastream asserts that it is a valid ISO-formatted video file using ftyp {$mp4_ftyp}"; |
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$fail = "{$datastream} datastream is not a valid ISO-formatted video"; |
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$results = islandora_assert_valid(strpos($mp4, 'ftyp'), $results, $pass, $fail); |
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return $results; |
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} |
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/** |
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* Attempts to validate an .ogg/ogv datastream using Vorbis and Theora encoding. |
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* |
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* OGG files are made up of several 'pages' of OGG data, each prefaced with an |
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* OGG marker - the letters 'OggS'. The file header also contains information on |
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* what encoders were used to create the file. Here, we're looking for at least |
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* one OGG page, and confirming that the file asserts the Theora and Vorbis |
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* codecs were used to create the file. |
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* |
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|
* @param AbstractObject $object |
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|
* The PID of the object. |
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|
* @param string $datastream |
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|
* A DSID of a datastream corresponding to an ogg file. |
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* |
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* @return array |
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* A series of TRUE(pass)/FALSE(fail) results paired with result messages. |
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*/ |
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function islandora_validate_ogg_datastream($object, $datastream) { |
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$results = array(); |
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$ogg = $object[$datastream]->content; |
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$ogg_pages = substr_count($ogg, 'OggS'); |
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$pass = "{$datastream} datastream asserts that it contains {$ogg_pages} Ogg pages (even a very small file should contain several)."; |
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$fail = "{$datastream} datastream contains no Ogg pages."; |
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$results = islandora_assert_valid(substr_count($ogg, 'OggS'), $results, $pass, $fail); |
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$pass = "{$datastream} datastream asserts that it contains Theora-encoded video data."; |
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$fail = "{$datastream} datastream contains no marker indicating the presence of Theora-encoded video data."; |
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$results = islandora_assert_valid(substr_count($ogg, 'theora'), $results, $pass, $fail); |
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$pass = "{$datastream} datastream asserts that it contains Vorbis-encoded audio data"; |
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$fail = "{$datastream} datastream contains no marker indicating the presence of Vorbis-encoded audio data."; |
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$results = islandora_assert_valid(substr_count($ogg, 'vorbis'), $results, $pass, $fail); |
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return $results; |
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} |
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/** |
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* Attempts to validate an .mkv datastream. |
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* |
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* There's not much we can do to check an MKV file, since the format is really, |
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* really loose. We do know a couple of things though - first, since MKV is an |
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* EBML format, the first four characters will always be the same. Since they're |
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* non-standard characters, we're looking at their hex values instead. And |
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* second, we know that the file will contain the declaration 'matroska' soon |
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* after. We could look for this in the binary, but we already have the hex- |
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* translated version, so we just look for 'matroska' in hex. |
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|
* |
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|
|
* @param AbstractObject $object |
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|
|
* The PID of the object. |
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|
|
* @param string $datastream |
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|
|
* A DSID of a datastream corresponding to an MKV file. |
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|
* |
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|
* @return array |
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|
|
* A series of TRUE(pass)/FALSE(fail) results paired with result messages. |
|
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|
|
*/ |
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|
|
function islandora_validate_mkv_datastream($object, $datastream) { |
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|
$results = array(); |
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|
$mkv = bin2hex($object[$datastream]->content); |
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$pass = "{$datastream} datastream asserts that it is an EBML-formatted file"; |
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$fail = "{$datastream} datastream is not an EBML-formatted file."; |
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$results = islandora_assert_valid(substr($mkv, 0, 8) == '1a45dfa3', $results, $pass, $fail); |
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$pass = "{$datastream} datastream asserts that its EBML DocType is Matroska"; |
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$fail = "{$datastream} datastream does not contain a Matroska EBML DocType marker."; |
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$results = islandora_assert_valid(substr_count($mkv, '6d6174726f736b61') == 1, $results, $pass, $fail); |
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return $results; |
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} |
Nelson Hart
11 years ago
