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FPDI/pdf_parser.php
Dave Umrysh 0a47a984e0 first commit
2022-12-30 13:48:08 -07:00

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<?php
/**
* This file is part of FPDI
*
* @package FPDI
* @copyright Copyright (c) 2017 Setasign - Jan Slabon (https://www.setasign.com)
* @license http://opensource.org/licenses/mit-license The MIT License
* @version 1.6.2
*/
/**
* Class pdf_parser
*/
class pdf_parser
{
/**
* Type constant
*
* @var integer
*/
const TYPE_NULL = 0;
/**
* Type constant
*
* @var integer
*/
const TYPE_NUMERIC = 1;
/**
* Type constant
*
* @var integer
*/
const TYPE_TOKEN = 2;
/**
* Type constant
*
* @var integer
*/
const TYPE_HEX = 3;
/**
* Type constant
*
* @var integer
*/
const TYPE_STRING = 4;
/**
* Type constant
*
* @var integer
*/
const TYPE_DICTIONARY = 5;
/**
* Type constant
*
* @var integer
*/
const TYPE_ARRAY = 6;
/**
* Type constant
*
* @var integer
*/
const TYPE_OBJDEC = 7;
/**
* Type constant
*
* @var integer
*/
const TYPE_OBJREF = 8;
/**
* Type constant
*
* @var integer
*/
const TYPE_OBJECT = 9;
/**
* Type constant
*
* @var integer
*/
const TYPE_STREAM = 10;
/**
* Type constant
*
* @var integer
*/
const TYPE_BOOLEAN = 11;
/**
* Type constant
*
* @var integer
*/
const TYPE_REAL = 12;
/**
* Define the amount of byte in which the initial keyword of a PDF document should be searched.
*
* @var int
*/
static public $searchForStartxrefLength = 5500;
/**
* Filename
*
* @var string
*/
public $filename;
/**
* File resource
*
* @var resource
*/
protected $_f;
/**
* PDF Context
*
* @var pdf_context
*/
protected $_c;
/**
* xref-Data
*
* @var array
*/
protected $_xref;
/**
* Data of the Root object
*
* @var array
*/
protected $_root;
/**
* PDF version of the loaded document
*
* @var string
*/
protected $_pdfVersion;
/**
* For reading encrypted documents and xref/object streams are in use
*
* @var boolean
*/
protected $_readPlain = true;
/**
* The current read object
*
* @var array
*/
protected $_currentObj;
/**
* Constructor
*
* @param string $filename Source filename
* @throws InvalidArgumentException
*/
public function __construct($filename)
{
$this->filename = $filename;
$this->_f = @fopen($this->filename, 'rb');
if (!$this->_f) {
throw new InvalidArgumentException(sprintf('Cannot open %s !', $filename));
}
$this->getPdfVersion();
if (!class_exists('pdf_context')) {
require_once('pdf_context.php');
}
$this->_c = new pdf_context($this->_f);
// Read xref-Data
$this->_xref = array();
$this->_readXref($this->_xref, $this->_findXref());
// Check for Encryption
$this->getEncryption();
// Read root
$this->_readRoot();
}
/**
* Destructor
*/
public function __destruct()
{
$this->closeFile();
}
/**
* Close the opened file
*/
public function closeFile()
{
if (isset($this->_f) && is_resource($this->_f)) {
fclose($this->_f);
unset($this->_f);
}
}
/**
* Check Trailer for Encryption
*
* @throws Exception
*/
public function getEncryption()
{
if (isset($this->_xref['trailer'][1]['/Encrypt'])) {
throw new Exception('File is encrypted!');
}
}
/**
* Get PDF-Version
*
* @return string
*/
public function getPdfVersion()
{
if ($this->_pdfVersion === null) {
fseek($this->_f, 0);
preg_match('/\d\.\d/', fread($this->_f, 16), $m);
if (isset($m[0]))
$this->_pdfVersion = $m[0];
}
return $this->_pdfVersion;
}
/**
* Read the /Root dictionary
*/
protected function _readRoot()
{
if ($this->_xref['trailer'][1]['/Root'][0] != self::TYPE_OBJREF) {
throw new Exception('Wrong Type of Root-Element! Must be an indirect reference');
}
$this->_root = $this->resolveObject($this->_xref['trailer'][1]['/Root']);
}
/**
* Find the xref table
*
* @return integer
* @throws Exception
*/
protected function _findXref()
{
$toRead = self::$searchForStartxrefLength;
$stat = fseek($this->_f, -$toRead, SEEK_END);
if ($stat === -1) {
fseek($this->_f, 0);
}
$data = fread($this->_f, $toRead);
$keywordPos = strpos(strrev($data), strrev('startxref'));
if (false === $keywordPos) {
$keywordPos = strpos(strrev($data), strrev('startref'));
}
if (false === $keywordPos) {
throw new Exception('Unable to find "startxref" keyword.');
}
$pos = strlen($data) - $keywordPos;
$data = substr($data, $pos);
if (!preg_match('/\s*(\d+).*$/s', $data, $matches)) {
throw new Exception('Unable to find pointer to xref table.');
}
return (int) $matches[1];
}
/**
* Read the xref table
*
* @param array $result Array of xref table entries
* @param integer $offset of xref table
* @return boolean
* @throws Exception
*/
protected function _readXref(&$result, $offset)
{
$tempPos = $offset - min(20, $offset);
fseek($this->_f, $tempPos); // set some bytes backwards to fetch corrupted docs
$data = fread($this->_f, 100);
$xrefPos = strrpos($data, 'xref');
if ($xrefPos === false) {
$this->_c->reset($offset);
$xrefStreamObjDec = $this->_readValue($this->_c);
if (is_array($xrefStreamObjDec) && isset($xrefStreamObjDec[0]) && $xrefStreamObjDec[0] == self::TYPE_OBJDEC) {
throw new Exception(
sprintf(
'This document (%s) probably uses a compression technique which is not supported by the ' .
'free parser shipped with FPDI. (See https://www.setasign.com/fpdi-pdf-parser for more details)',
$this->filename
)
);
} else {
throw new Exception('Unable to find xref table.');
}
}
if (!isset($result['xrefLocation'])) {
$result['xrefLocation'] = $tempPos + $xrefPos;
$result['maxObject'] = 0;
}
$cycles = -1;
$bytesPerCycle = 100;
fseek($this->_f, $tempPos = $tempPos + $xrefPos + 4); // set the handle directly after the "xref"-keyword
$data = fread($this->_f, $bytesPerCycle);
while (($trailerPos = strpos($data, 'trailer', max($bytesPerCycle * $cycles++, 0))) === false && !feof($this->_f)) {
$data .= fread($this->_f, $bytesPerCycle);
}
if ($trailerPos === false) {
throw new Exception('Trailer keyword not found after xref table');
}
$data = ltrim(substr($data, 0, $trailerPos));
// get Line-Ending
$found = preg_match_all("/(\r\n|\n|\r)/", substr($data, 0, 100), $m); // check the first 100 bytes for line breaks
if ($found === 0) {
throw new Exception('Xref table seems to be corrupted.');
}
$differentLineEndings = count(array_unique($m[0]));
if ($differentLineEndings > 1) {
$lines = preg_split("/(\r\n|\n|\r)/", $data, -1, PREG_SPLIT_NO_EMPTY);
} else {
$lines = explode($m[0][0], $data);
}
$data = $differentLineEndings = $m = null;
unset($data, $differentLineEndings, $m);
$linesCount = count($lines);
$start = 1;
for ($i = 0; $i < $linesCount; $i++) {
$line = trim($lines[$i]);
if ($line) {
$pieces = explode(' ', $line);
$c = count($pieces);
switch($c) {
case 2:
$start = (int)$pieces[0];
$end = $start + (int)$pieces[1];
if ($end > $result['maxObject'])
$result['maxObject'] = $end;
break;
case 3:
if (!isset($result['xref'][$start]))
$result['xref'][$start] = array();
if (!array_key_exists($gen = (int) $pieces[1], $result['xref'][$start])) {
$result['xref'][$start][$gen] = $pieces[2] == 'n' ? (int) $pieces[0] : null;
}
$start++;
break;
default:
throw new Exception('Unexpected data in xref table');
}
}
}
$lines = $pieces = $line = $start = $end = $gen = null;
unset($lines, $pieces, $line, $start, $end, $gen);
$this->_c->reset($tempPos + $trailerPos + 7);
$trailer = $this->_readValue($this->_c);
if (!isset($result['trailer'])) {
$result['trailer'] = $trailer;
}
if (isset($trailer[1]['/Prev'])) {
$this->_readXref($result, $trailer[1]['/Prev'][1]);
}
$trailer = null;
unset($trailer);
return true;
}
/**
* Reads a PDF value
*
* @param pdf_context $c
* @param string $token A token
* @return mixed
* @throws Exception
*/
protected function _readValue(&$c, $token = null)
{
if (is_null($token)) {
$token = $this->_readToken($c);
}
if ($token === false) {
return false;
}
switch ($token) {
case '<':
// This is a hex string.
// Read the value, then the terminator
$pos = $c->offset;
while(1) {
$match = strpos($c->buffer, '>', $pos);
// If you can't find it, try
// reading more data from the stream
if ($match === false) {
if (!$c->increaseLength()) {
return false;
} else {
continue;
}
}
$result = substr($c->buffer, $c->offset, $match - $c->offset);
$c->offset = $match + 1;
return array (self::TYPE_HEX, $result);
}
break;
case '<<':
// This is a dictionary.
$result = array();
// Recurse into this function until we reach
// the end of the dictionary.
while (($key = $this->_readToken($c)) !== '>>') {
if ($key === false) {
return false;
}
if (($value = $this->_readValue($c)) === false) {
return false;
}
// Catch missing value
if ($value[0] == self::TYPE_TOKEN && $value[1] == '>>') {
$result[$key] = array(self::TYPE_NULL);
break;
}
$result[$key] = $value;
}
return array (self::TYPE_DICTIONARY, $result);
case '[':
// This is an array.
$result = array();
// Recurse into this function until we reach
// the end of the array.
while (($token = $this->_readToken($c)) !== ']') {
if ($token === false) {
return false;
}
if (($value = $this->_readValue($c, $token)) === false) {
return false;
}
$result[] = $value;
}
return array (self::TYPE_ARRAY, $result);
case '(':
// This is a string
$pos = $c->offset;
$openBrackets = 1;
do {
for (; $openBrackets != 0 && $pos < $c->length; $pos++) {
switch (ord($c->buffer[$pos])) {
case 0x28: // '('
$openBrackets++;
break;
case 0x29: // ')'
$openBrackets--;
break;
case 0x5C: // backslash
$pos++;
}
}
} while($openBrackets != 0 && $c->increaseLength());
$result = substr($c->buffer, $c->offset, $pos - $c->offset - 1);
$c->offset = $pos;
return array (self::TYPE_STRING, $result);
case 'stream':
$tempPos = $c->getPos() - strlen($c->buffer);
$tempOffset = $c->offset;
$c->reset($startPos = $tempPos + $tempOffset);
// Find the first "newline"
while ($c->buffer[0] !== chr(10) && $c->buffer[0] !== chr(13)) {
$c->reset(++$startPos);
if ($c->ensureContent() === false) {
throw new Exception(
'Unable to parse stream data. No newline followed the stream keyword.'
);
}
}
$e = 0; // ensure line breaks in front of the stream
if ($c->buffer[0] == chr(10) || $c->buffer[0] == chr(13))
$e++;
if ($c->buffer[1] == chr(10) && $c->buffer[0] != chr(10))
$e++;
if ($this->_currentObj[1][1]['/Length'][0] == self::TYPE_OBJREF) {
$tmpLength = $this->resolveObject($this->_currentObj[1][1]['/Length']);
$length = $tmpLength[1][1];
} else {
$length = $this->_currentObj[1][1]['/Length'][1];
}
if ($length > 0) {
$c->reset($startPos + $e, $length);
$v = $c->buffer;
} else {
$v = '';
}
$c->reset($startPos + $e + $length);
$endstream = $this->_readToken($c);
if ($endstream != 'endstream') {
$c->reset($startPos + $e + $length + 9); // 9 = strlen("endstream")
// We don't throw an error here because the next
// round trip will start at a new offset
}
return array(self::TYPE_STREAM, $v);
default:
if (is_numeric($token)) {
// A numeric token. Make sure that
// it is not part of something else.
if (($tok2 = $this->_readToken($c)) !== false) {
if (is_numeric($tok2)) {
// Two numeric tokens in a row.
// In this case, we're probably in
// front of either an object reference
// or an object specification.
// Determine the case and return the data
if (($tok3 = $this->_readToken($c)) !== false) {
switch ($tok3) {
case 'obj':
return array(self::TYPE_OBJDEC, (int)$token, (int)$tok2);
case 'R':
return array(self::TYPE_OBJREF, (int)$token, (int)$tok2);
}
// If we get to this point, that numeric value up
// there was just a numeric value. Push the extra
// tokens back into the stack and return the value.
array_push($c->stack, $tok3);
}
}
array_push($c->stack, $tok2);
}
if ($token === (string)((int)$token))
return array(self::TYPE_NUMERIC, (int)$token);
else
return array(self::TYPE_REAL, (float)$token);
} else if ($token == 'true' || $token == 'false') {
return array(self::TYPE_BOOLEAN, $token == 'true');
} else if ($token == 'null') {
return array(self::TYPE_NULL);
} else {
// Just a token. Return it.
return array(self::TYPE_TOKEN, $token);
}
}
}
/**
* Resolve an object
*
* @param array $objSpec The object-data
* @return array|boolean
* @throws Exception
*/
public function resolveObject($objSpec)
{
$c = $this->_c;
// Exit if we get invalid data
if (!is_array($objSpec)) {
return false;
}
if ($objSpec[0] == self::TYPE_OBJREF) {
// This is a reference, resolve it
if (isset($this->_xref['xref'][$objSpec[1]][$objSpec[2]])) {
// Save current file position
// This is needed if you want to resolve
// references while you're reading another object
// (e.g.: if you need to determine the length
// of a stream)
$oldPos = $c->getPos();
// Reposition the file pointer and
// load the object header.
$c->reset($this->_xref['xref'][$objSpec[1]][$objSpec[2]]);
$header = $this->_readValue($c);
if ($header[0] != self::TYPE_OBJDEC || $header[1] != $objSpec[1] || $header[2] != $objSpec[2]) {
$toSearchFor = $objSpec[1] . ' ' . $objSpec[2] . ' obj';
if (preg_match('/' . $toSearchFor . '/', $c->buffer)) {
$c->offset = strpos($c->buffer, $toSearchFor) + strlen($toSearchFor);
// reset stack
$c->stack = array();
} else {
throw new Exception(
sprintf("Unable to find object (%s, %s) at expected location.", $objSpec[1], $objSpec[2])
);
}
}
// If we're being asked to store all the information
// about the object, we add the object ID and generation
// number for later use
$result = array (
self::TYPE_OBJECT,
'obj' => $objSpec[1],
'gen' => $objSpec[2]
);
$this->_currentObj =& $result;
// Now simply read the object data until
// we encounter an end-of-object marker
while (true) {
$value = $this->_readValue($c);
if ($value === false || count($result) > 4) {
// in this case the parser couldn't find an "endobj" so we break here
break;
}
if ($value[0] == self::TYPE_TOKEN && $value[1] === 'endobj') {
break;
}
$result[] = $value;
}
$c->reset($oldPos);
if (isset($result[2][0]) && $result[2][0] == self::TYPE_STREAM) {
$result[0] = self::TYPE_STREAM;
}
} else {
throw new Exception(
sprintf("Unable to find object (%s, %s) at expected location.", $objSpec[1], $objSpec[2])
);
}
return $result;
} else {
return $objSpec;
}
}
/**
* Reads a token from the context
*
* @param pdf_context $c
* @return mixed
*/
protected function _readToken($c)
{
// If there is a token available
// on the stack, pop it out and
// return it.
if (count($c->stack)) {
return array_pop($c->stack);
}
// Strip away any whitespace
do {
if (!$c->ensureContent()) {
return false;
}
$c->offset += strspn($c->buffer, "\x20\x0A\x0C\x0D\x09\x00", $c->offset);
} while ($c->offset >= $c->length - 1);
// Get the first character in the stream
$char = $c->buffer[$c->offset++];
switch ($char) {
case '[':
case ']':
case '(':
case ')':
// This is either an array or literal string
// delimiter, Return it
return $char;
case '<':
case '>':
// This could either be a hex string or
// dictionary delimiter. Determine the
// appropriate case and return the token
if ($c->buffer[$c->offset] == $char) {
if (!$c->ensureContent()) {
return false;
}
$c->offset++;
return $char . $char;
} else {
return $char;
}
case '%':
// This is a comment - jump over it!
$pos = $c->offset;
while(1) {
$match = preg_match("/(\r\n|\r|\n)/", $c->buffer, $m, PREG_OFFSET_CAPTURE, $pos);
if ($match === 0) {
if (!$c->increaseLength()) {
return false;
} else {
continue;
}
}
$c->offset = $m[0][1] + strlen($m[0][0]);
return $this->_readToken($c);
}
default:
// This is "another" type of token (probably
// a dictionary entry or a numeric value)
// Find the end and return it.
if (!$c->ensureContent()) {
return false;
}
while(1) {
// Determine the length of the token
$pos = strcspn($c->buffer, "\x20%[]<>()/\x0A\x0C\x0D\x09\x00", $c->offset);
if ($c->offset + $pos <= $c->length - 1) {
break;
} else {
// If the script reaches this point,
// the token may span beyond the end
// of the current buffer. Therefore,
// we increase the size of the buffer
// and try again--just to be safe.
$c->increaseLength();
}
}
$result = substr($c->buffer, $c->offset - 1, $pos + 1);
$c->offset += $pos;
return $result;
}
}
/**
* Un-filter a stream object
*
* @param array $obj
* @return string
* @throws Exception
*/
protected function _unFilterStream($obj)
{
$filters = array();
if (isset($obj[1][1]['/Filter'])) {
$filter = $obj[1][1]['/Filter'];
if ($filter[0] == pdf_parser::TYPE_OBJREF) {
$tmpFilter = $this->resolveObject($filter);
$filter = $tmpFilter[1];
}
if ($filter[0] == pdf_parser::TYPE_TOKEN) {
$filters[] = $filter;
} else if ($filter[0] == pdf_parser::TYPE_ARRAY) {
$filters = $filter[1];
}
}
$stream = $obj[2][1];
foreach ($filters AS $filter) {
switch ($filter[1]) {
case '/FlateDecode':
case '/Fl':
if (function_exists('gzuncompress')) {
$oStream = $stream;
$stream = (strlen($stream) > 0) ? @gzuncompress($stream) : '';
} else {
throw new Exception(
sprintf('To handle %s filter, please compile php with zlib support.', $filter[1])
);
}
if ($stream === false) {
$tries = 0;
while ($tries < 8 && ($stream === false || strlen($stream) < strlen($oStream))) {
$oStream = substr($oStream, 1);
$stream = @gzinflate($oStream);
$tries++;
}
if ($stream === false) {
throw new Exception('Error while decompressing stream.');
}
}
break;
case '/LZWDecode':
if (!class_exists('FilterLZW')) {
require_once('filters/FilterLZW.php');
}
$decoder = new FilterLZW();
$stream = $decoder->decode($stream);
break;
case '/ASCII85Decode':
if (!class_exists('FilterASCII85')) {
require_once('filters/FilterASCII85.php');
}
$decoder = new FilterASCII85();
$stream = $decoder->decode($stream);
break;
case '/ASCIIHexDecode':
if (!class_exists('FilterASCIIHexDecode')) {
require_once('filters/FilterASCIIHexDecode.php');
}
$decoder = new FilterASCIIHexDecode();
$stream = $decoder->decode($stream);
break;
case null:
break;
default:
throw new Exception(sprintf('Unsupported Filter: %s', $filter[1]));
}
}
return $stream;
}
}
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