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vichan/inc/lib/webm/matroska.php

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<?php
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/* This file is dedicated to the public domain; you may do as you wish with it. */
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// Information needed to parse an element type
class EBMLElementType {
public $name;
public $datatype;
public $validParents;
}
// Information needed to parse all possible element types in a document
class EBMLElementTypeList {
private $_els;
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private $_ids;
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public function __construct($filename) {
$lines = file($filename);
foreach($lines as $line) {
$fields = explode(' ', trim($line));
$t = new EBMLElementType;
$id = hexdec($fields[0]);
$t->datatype = $fields[1];
$t->name = $fields[2];
$t->validParents = array();
for ($i = 0; $i + 3 < count($fields); $i++) {
if ($fields[$i+3] == '*' || $fields[$i+3] == 'root') {
$t->validParents[$i] = $fields[$i+3];
} else {
$t->validParents[$i] = hexdec($fields[$i+3]);
}
}
$this->_els[$id] = $t;
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$this->_ids[strtoupper($t->name)] = $id;
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}
}
public function exists($id) {
return isset($this->_els[$id]);
}
public function name($id) {
if (!isset($this->_els[$id])) return NULL;
return $this->_els[$id]->name;
}
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public function id($name) {
$name = strtoupper($name);
if (!isset($this->_ids[$name])) return NULL;
return $this->_ids[$name];
}
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public function datatype($id) {
if ($id == 'root') return 'container';
if (!isset($this->_els[$id])) return 'binary';
return $this->_els[$id]->datatype;
}
public function validChild($id1, $id2) {
if (!isset($this->_els[$id2])) return TRUE;
$parents = $this->_els[$id2]->validParents;
return in_array('*', $parents) || in_array($id1, $parents);
}
}
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// Matroska element types
global $EBML_ELEMENTS;
$EBML_ELEMENTS = new EBMLElementTypeList(dirname(__FILE__) . '/matroska-elements.txt');
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// Decode big-endian integer
function ebmlDecodeInt($data, $signed=FALSE, $carryIn=0) {
$n = $carryIn;
if (strlen($data) > 8) throw new Exception('not supported: integer too long');
for ($i = 0; $i < strlen($data); $i++) {
if ($n > (PHP_INT_MAX >> 8) || $n < ((-PHP_INT_MAX-1) >> 8)) {
$n = floatval($n);
}
$n = $n * 0x100 + ord($data[$i]);
if ($i == 0 && $signed && ($n & 0x80) != 0) {
$n -= 0x100;
}
}
return $n;
}
// Decode big-endian IEEE float
function ebmlDecodeFloat($data) {
switch (strlen($data)) {
case 0:
return 0;
case 4:
switch(pack('f', 1e9)) {
case '(knN':
$arr = unpack('f', strrev($data));
return $arr[1];
case 'Nnk(':
$arr = unpack('f', $data);
return $arr[1];
default:
error_log('cannot decode floats');
return NULL;
}
case 8:
switch(pack('d', 1e9)) {
case "\x00\x00\x00\x00\x65\xcd\xcd\x41":
$arr = unpack('d', strrev($data));
return $arr[1];
case "\x41\xcd\xcd\x65\x00\x00\x00\x00":
$arr = unpack('d', $data);
return $arr[1];
default:
error_log('cannot decode floats');
return NULL;
}
default:
error_log('unsupported float length');
return NULL;
}
}
// Decode big-endian signed offset from Jan 01, 2000 in nanoseconds
// Convert to offset from Jan 01, 1970 in seconds
function ebmlDecodeDate($data) {
return ebmlDecodeInt($data, TRUE) * 1e-9 + 946684800;
}
// Decode data of specified datatype
function ebmlDecode($data, $datatype) {
switch ($datatype) {
case 'int': return ebmlDecodeInt($data, TRUE);
case 'uint': return ebmlDecodeInt($data, FALSE);
case 'float': return ebmlDecodeFloat($data);
case 'string': return chop($data, "\0");
case 'date': return ebmlDecodeDate($data);
case 'binary': return $data;
default: throw new Exception('unknown datatype');
}
}
// Methods for reading data from section of EBML file
class EBMLReader {
private $_fileHandle;
private $_offset;
private $_size;
private $_position;
public function __construct($fileHandle, $offset=0, $size=NULL) {
$this->_fileHandle = $fileHandle;
$this->_offset = $offset;
$this->_size = $size;
$this->_position = 0;
}
// Tell position within data section
public function position() {
return $this->_position;
}
// Set position within data section
public function setPosition($position) {
$this->_position = $position;
}
// Total size of data section (NULL if unknown)
public function size() {
return $this->_size;
}
// Set end of data section
public function setSize($size) {
if ($this->_size === NULL) {
$this->_size = $size;
} else {
throw new Exception('size already set');
}
}
// Determine whether we are at end of data
public function endOfData() {
if ($this->_size === NULL) {
fseek($this->_fileHandle, $this->_offset + $this->_position);
fread($this->_fileHandle, 1);
if (feof($this->_fileHandle)) {
$this->_size = $this->_position;
return TRUE;
} else {
return FALSE;
}
} else {
return $this->_position >= $this->_size;
}
}
// Create EBMLReader containing $size bytes and advance
public function nextSlice($size) {
$slice = new EBMLReader($this->_fileHandle, $this->_offset + $this->_position, $size);
if ($size !== NULL) {
$this->_position += $size;
if ($this->_size !== NULL && $this->_position > $this->_size) {
throw new Exception('unexpected end of data');
}
}
return $slice;
}
// Read entire region
public function readAll() {
if ($this->_size == 0) return '';
if ($this->_size === NULL) throw new Exception('unknown length');
fseek($this->_fileHandle, $this->_offset);
$data = fread($this->_fileHandle, $this->_size);
if ($data === FALSE || strlen($data) != $this->_size) {
throw new Exception('error reading from file');
}
return $data;
}
// Read $size bytes
public function read($size) {
return $this->nextSlice($size)->readAll();
}
// Read variable-length integer
public function readVarInt($signed=FALSE) {
// Read size and remove flag
$n = ord($this->read(1));
$size = 0;
if ($n == 0) {
throw new Exception('not supported: variable-length integer too long');
}
$flag = 0x80;
while (($n & $flag) == 0) {
$flag = $flag >> 1;
$size++;
}
$n -= $flag;
// Read remaining data
$rawInt = $this->read($size);
// Check for all ones
if ($n == $flag - 1 && $rawInt == str_repeat("\xFF", $size)) {
return NULL;
}
// Range shift for signed integers
if ($signed) {
if ($flag == 0x01) {
$n = ord($rawInt[0]) - 0x80;
$rawInt = $rawInt.substr(1);
} else {
$n -= ($flag >> 1);
}
}
// Convert to integer
$n = ebmlDecodeInt($rawInt, FALSE, $n);
// Range shift for signed integers
if ($signed) {
if ($n == PHP_INT_MAX) {
$n = floatval($n);
}
$n++;
}
return $n;
}
}
// EBML element
class EBMLElement {
private $_id;
private $_name;
private $_datatype;
private $_content;
private $_headSize;
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public function __construct($id, $content, $headSize) {
global $EBML_ELEMENTS;
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$this->_id = $id;
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$this->_name = $EBML_ELEMENTS->name($this->_id);
$this->_datatype = $EBML_ELEMENTS->datatype($this->_id);
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$this->_content = $content;
$this->_headSize = $headSize;
}
public function id() {return $this->_id;}
public function name() {return $this->_name;}
public function datatype() {return $this->_datatype;}
public function content() {return $this->_content;}
public function headSize() {return $this->_headSize;}
// Total size of element (including ID and datasize)
public function size() {
return $this->_headSize + $this->_content->size();
}
// Read and interpret content
public function value() {
if ($this->_datatype == 'binary') {
return $this->_content;
} else {
return ebmlDecode($this->_content->readAll(), $this->_datatype);
}
}
}
// Iterate over EBML elements in data
class EBMLElementList extends EBMLElement implements Iterator {
private $_cache;
private $_position;
private static $MAX_ELEMENTS = 10000;
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public function __construct($id, $content, $headSize) {
parent::__construct($id, $content, $headSize);
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$this->_cache = array();
$this->_position = 0;
}
public function rewind() {
$this->_position = 0;
}
public function current() {
if ($this->valid()) {
return $this->_cache[$this->_position];
} else {
return NULL;
}
}
public function key() {
return $this->_position;
}
public function next() {
$this->_position += $this->current()->size();
if ($this->content()->size() !== NULL && $this->_position > $this->content()->size()) {
throw new Exception('unexpected end of data');
}
}
public function valid() {
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global $EBML_ELEMENTS;
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if (isset($this->_cache[$this->_position])) return TRUE;
$this->content()->setPosition($this->_position);
if ($this->content()->endOfData()) return FALSE;
$id = $this->content()->readVarInt();
if ($id === NULL) throw new Exception('invalid ID');
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if ($this->content()->size() === NULL && !$EBML_ELEMENTS->validChild($this->id(), $id)) {
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$this->content()->setSize($this->_position);
return FALSE;
}
$size = $this->content()->readVarInt();
$headSize = $this->content()->position() - $this->_position;
$content = $this->content()->nextSlice($size);
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if ($EBML_ELEMENTS->datatype($id) == 'container') {
$element = new EBMLElementList($id, $content, $headSize);
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} else {
if ($size === NULL) {
throw new Exception('non-container element of unknown size');
}
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$element = new EBMLElement($id, $content, $headSize);
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}
$this->_cache[$this->_position] = $element;
return TRUE;
}
// Total size of element (including ID and size)
public function size() {
if ($this->content()->size() === NULL) {
$iElement = 0;
foreach ($this as $element) { // iterate over elements to find end
$iElement++;
if ($iElement > self::$MAX_ELEMENTS) throw new Exception('not supported: too many elements');
}
}
return $this->headSize() + $this->content()->size();
}
// Read and interpret content
public function value() {
return $this;
}
// Get element value by name
public function get($name, $defaultValue=NULL) {
$iElement = 0;
foreach ($this as $element) {
$iElement++;
if ($iElement > self::$MAX_ELEMENTS) throw new Exception('not supported: too many elements');
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if (strtoupper($element->name()) == strtoupper($name)) {
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return $element->value();
}
}
return $defaultValue;
}
}
// Parse block
class MatroskaBlock {
const LACING_NONE = 0;
const LACING_XIPH = 1;
const LACING_EBML = 3;
const LACING_FIXED = 2;
public $trackNumber;
public $timecode;
public $keyframe;
public $invisible;
public $lacing;
public $discardable;
public $frames;
public function __construct($reader) {
# Header
$this->trackNumber = $reader->readVarInt();
$this->timecode = ebmlDecodeInt($reader->read(2), TRUE);
$flags = ord($reader->read(1));
if (($flags & 0x70) != 0) {
throw new Exception('reserved flags set');
}
$this->keyframe = (($flags & 0x80) != 0);
$this->invisible = (($flags & 0x08) != 0);
$this->lacing = ($flags >> 1) & 0x03;
$this->discardable = (($flags & 0x01) != 0);
# Lacing sizes
if ($this->lacing == self::LACING_NONE) {
$nsizes = 0;
} else {
$nsizes = ord($reader->read(1));
}
$sizes = array();
switch ($this->lacing) {
case self::LACING_XIPH:
for ($i = 0; $i < $nsizes; $i++) {
$size = 0;
$x = 255;
while ($x == 255) {
$x = ord($reader->read(1));
$size += $x;
if ($size > 65536) throw new Exception('not supported: laced frame too long');
}
$sizes[$i] = $size;
}
break;
case self::LACING_EBML:
$size = 0;
for ($i = 0; $i < $nsizes; $i++) {
$dsize = $reader->readVarInt($i != 0);
if ($dsize === NULL || $size + $dsize < 0) {
throw new Exception('invalid frame size');
}
$size += $dsize;
$sizes[$i] = $size;
}
break;
case self::LACING_FIXED:
$lenRemaining = $reader->size() - $reader->position();
if ($lenRemaining % ($nsizes + 1) != 0) {
throw new Exception('data size not divisible by frame count');
}
$size = (int) ($lenRemaining / ($nsizes + 1));
for ($i = 0; $i < $nsizes; $i++) {
$sizes[$i] = $size;
}
break;
}
# Frames
$this->frames = array();
for ($i = 0; $i < $nsizes; $i++) {
$this->frames[$i] = $reader->nextSlice($sizes[$i]);
}
$this->frames[$nsizes] = $reader->nextSlice($reader->size() - $reader->position());
}
}
// Create element list from $fileHandle
function readMatroska($fileHandle) {
$reader = new EBMLReader($fileHandle);
if ($reader->read(4) != "\x1a\x45\xdf\xa3") {
throw new Exception('not an EBML file');
}
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$root = new EBMLElementList('root', $reader, 0);
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$header = $root->get('EBML');
$ebmlVersion = $header->get('EBMLReadVersion', 1);
$docType = $header->get('DocType');
$docTypeVersion = $header->get('DocTypeReadVersion', 1);
if ($ebmlVersion != 1) {
throw new Exception('unsupported EBML version');
}
if ($docType != 'matroska' && $docType != 'webm') {
throw new Exception ('unsupported document type');
}
if ($docTypeVersion < 1 || $docTypeVersion > 4) {
throw new Exception ('unsupported document type version');
}
return $root;
}
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function ebmlEncodeVarInt($n) {
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$data = '';
$flag = 0x80;
while ($n >= $flag) {
if ($flag == 0) {
throw new Exception('not supported: number too large');
}
$data = chr($n & 0xFF) . $data;
$n = $n >> 8;
$flag = $flag >> 1;
}
$data = chr($n | $flag) . $data;
return $data;
}
function ebmlEncodeElementName($name) {
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global $EBML_ELEMENTS;
return ebmlEncodeVarInt($EBML_ELEMENTS->id($name));
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}
function ebmlEncodeElement($name, $content) {
return ebmlEncodeElementName($name) . ebmlEncodeVarInt(strlen($content)) . $content;
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}