includes/utils/ZipDirectoryReader.php

   1 <?php
   2 /**
   3  * ZIP file directories reader, for the purposes of upload verification.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  */
  22
  23 /**
  24  * A class for reading ZIP file directories, for the purposes of upload
  25  * verification.
  26  *
  27  * Only a functional interface is provided: ZipFileReader::read(). No access is
  28  * given to object instances.
  29  *
  30  */
  31 class ZipDirectoryReader {
  32         /**
  33          * Read a ZIP file and call a function for each file discovered in it.
  34          *
  35          * Because this class is aimed at verification, an error is raised on
  36          * suspicious or ambiguous input, instead of emulating some standard
  37          * behavior.
  38          *
  39          * @param string $fileName The archive file name
  40          * @param array $callback The callback function. It will be called for each file
  41          *   with a single associative array each time, with members:
  42          *
  43          *      - name: The file name. Directories conventionally have a trailing
  44          *        slash.
  45          *
  46          *      - mtime: The file modification time, in MediaWiki 14-char format
  47          *
  48          *      - size: The uncompressed file size
  49          *
  50          * @param array $options An associative array of read options, with the option
  51          *    name in the key. This may currently contain:
  52          *
  53          *      - zip64: If this is set to true, then we will emulate a
  54          *        library with ZIP64 support, like OpenJDK 7. If it is set to
  55          *        false, then we will emulate a library with no knowledge of
  56          *        ZIP64.
  57          *
  58          *        NOTE: The ZIP64 code is untested and probably doesn't work. It
  59          *        turned out to be easier to just reject ZIP64 archive uploads,
  60          *        since they are likely to be very rare. Confirming safety of a
  61          *        ZIP64 file is fairly complex. What do you do with a file that is
  62          *        ambiguous and broken when read with a non-ZIP64 reader, but valid
  63          *        when read with a ZIP64 reader? This situation is normal for a
  64          *        valid ZIP64 file, and working out what non-ZIP64 readers will make
  65          *        of such a file is not trivial.
  66          *
  67          * @return Status A Status object. The following fatal errors are defined:
  68          *
  69          *      - zip-file-open-error: The file could not be opened.
  70          *
  71          *      - zip-wrong-format: The file does not appear to be a ZIP file.
  72          *
  73          *      - zip-bad: There was something wrong or ambiguous about the file
  74          *        data.
  75          *
  76          *      - zip-unsupported: The ZIP file uses features which
  77          *        ZipDirectoryReader does not support.
  78          *
  79          * The default messages for those fatal errors are written in a way that
  80          * makes sense for upload verification.
  81          *
  82          * If a fatal error is returned, more information about the error will be
  83          * available in the debug log.
  84          *
  85          * Note that the callback function may be called any number of times before
  86          * a fatal error is returned. If this occurs, the data sent to the callback
  87          * function should be discarded.
  88          */
  89         public static function read( $fileName, $callback, $options = array() ) {
  90                 $zdr = new self( $fileName, $callback, $options );
  91
  92                 return $zdr->execute();
  93         }
  94
  95         /** The file name */
  96         protected $fileName;
  97
  98         /** The opened file resource */
  99         protected $file;
 100
 101         /** The cached length of the file, or null if it has not been loaded yet. */
 102         protected $fileLength;
 103
 104         /** A segmented cache of the file contents */
 105         protected $buffer;
 106
 107         /** The file data callback */
 108         protected $callback;
 109
 110         /** The ZIP64 mode */
 111         protected $zip64 = false;
 112
 113         /** Stored headers */
 114         protected $eocdr, $eocdr64, $eocdr64Locator;
 115
 116         protected $data;
 117
 118         /** The "extra field" ID for ZIP64 central directory entries */
 119         const ZIP64_EXTRA_HEADER = 0x0001;
 120
 121         /** The segment size for the file contents cache */
 122         const SEGSIZE = 16384;
 123
 124         /** The index of the "general field" bit for UTF-8 file names */
 125         const GENERAL_UTF8 = 11;
 126
 127         /** The index of the "general field" bit for central directory encryption */
 128         const GENERAL_CD_ENCRYPTED = 13;
 129
 130         /**
 131          * Private constructor
 132          * @param string $fileName
 133          * @param callable $callback
 134          * @param array $options
 135          */
 136         protected function __construct( $fileName, $callback, $options ) {
 137                 $this->fileName = $fileName;
 138                 $this->callback = $callback;
 139
 140                 if ( isset( $options['zip64'] ) ) {
 141                         $this->zip64 = $options['zip64'];
 142                 }
 143         }
 144
 145         /**
 146          * Read the directory according to settings in $this.
 147          *
 148          * @return Status
 149          */
 150         function execute() {
 151                 $this->file = fopen( $this->fileName, 'r' );
 152                 $this->data = array();
 153                 if ( !$this->file ) {
 154                         return Status::newFatal( 'zip-file-open-error' );
 155                 }
 156
 157                 $status = Status::newGood();
 158                 try {
 159                         $this->readEndOfCentralDirectoryRecord();
 160                         if ( $this->zip64 ) {
 161                                 list( $offset, $size ) = $this->findZip64CentralDirectory();
 162                                 $this->readCentralDirectory( $offset, $size );
 163                         } else {
 164                                 if ( $this->eocdr['CD size'] == 0xffffffff
 165                                         || $this->eocdr['CD offset'] == 0xffffffff
 166                                         || $this->eocdr['CD entries total'] == 0xffff
 167                                 ) {
 168                                         $this->error( 'zip-unsupported', 'Central directory header indicates ZIP64, ' .
 169                                                 'but we are in legacy mode. Rejecting this upload is necessary to avoid ' .
 170                                                 'opening vulnerabilities on clients using OpenJDK 7 or later.' );
 171                                 }
 172
 173                                 list( $offset, $size ) = $this->findOldCentralDirectory();
 174                                 $this->readCentralDirectory( $offset, $size );
 175                         }
 176                 } catch ( ZipDirectoryReaderError $e ) {
 177                         $status->fatal( $e->getErrorCode() );
 178                 }
 179
 180                 fclose( $this->file );
 181
 182                 return $status;
 183         }
 184
 185         /**
 186          * Throw an error, and log a debug message
 187          * @param mixed $code
 188          * @param string $debugMessage
 189          */
 190         function error( $code, $debugMessage ) {
 191                 wfDebug( __CLASS__ . ": Fatal error: $debugMessage\n" );
 192                 throw new ZipDirectoryReaderError( $code );
 193         }
 194
 195         /**
 196          * Read the header which is at the end of the central directory,
 197          * unimaginatively called the "end of central directory record" by the ZIP
 198          * spec.
 199          */
 200         function readEndOfCentralDirectoryRecord() {
 201                 $info = array(
 202                         'signature' => 4,
 203                         'disk' => 2,
 204                         'CD start disk' => 2,
 205                         'CD entries this disk' => 2,
 206                         'CD entries total' => 2,
 207                         'CD size' => 4,
 208                         'CD offset' => 4,
 209                         'file comment length' => 2,
 210                 );
 211                 $structSize = $this->getStructSize( $info );
 212                 $startPos = $this->getFileLength() - 65536 - $structSize;
 213                 if ( $startPos < 0 ) {
 214                         $startPos = 0;
 215                 }
 216
 217                 $block = $this->getBlock( $startPos );
 218                 $sigPos = strrpos( $block, "PK\x05\x06" );
 219                 if ( $sigPos === false ) {
 220                         $this->error( 'zip-wrong-format',
 221                                 "zip file lacks EOCDR signature. It probably isn't a zip file." );
 222                 }
 223
 224                 $this->eocdr = $this->unpack( substr( $block, $sigPos ), $info );
 225                 $this->eocdr['EOCDR size'] = $structSize + $this->eocdr['file comment length'];
 226
 227                 if ( $structSize + $this->eocdr['file comment length'] != strlen( $block ) - $sigPos ) {
 228                         $this->error( 'zip-bad', 'trailing bytes after the end of the file comment' );
 229                 }
 230                 if ( $this->eocdr['disk'] !== 0
 231                         || $this->eocdr['CD start disk'] !== 0
 232                 ) {
 233                         $this->error( 'zip-unsupported', 'more than one disk (in EOCDR)' );
 234                 }
 235                 $this->eocdr += $this->unpack(
 236                         $block,
 237                         array( 'file comment' => array( 'string', $this->eocdr['file comment length'] ) ),
 238                         $sigPos + $structSize );
 239                 $this->eocdr['position'] = $startPos + $sigPos;
 240         }
 241
 242         /**
 243          * Read the header called the "ZIP64 end of central directory locator". An
 244          * error will be raised if it does not exist.
 245          */
 246         function readZip64EndOfCentralDirectoryLocator() {
 247                 $info = array(
 248                         'signature' => array( 'string', 4 ),
 249                         'eocdr64 start disk' => 4,
 250                         'eocdr64 offset' => 8,
 251                         'number of disks' => 4,
 252                 );
 253                 $structSize = $this->getStructSize( $info );
 254
 255                 $start = $this->getFileLength() - $this->eocdr['EOCDR size'] - $structSize;
 256                 $block = $this->getBlock( $start, $structSize );
 257                 $this->eocdr64Locator = $data = $this->unpack( $block, $info );
 258
 259                 if ( $data['signature'] !== "PK\x06\x07" ) {
 260                         // Note: Java will allow this and continue to read the
 261                         // EOCDR64, so we have to reject the upload, we can't
 262                         // just use the EOCDR header instead.
 263                         $this->error( 'zip-bad', 'wrong signature on Zip64 end of central directory locator' );
 264                 }
 265         }
 266
 267         /**
 268          * Read the header called the "ZIP64 end of central directory record". It
 269          * may replace the regular "end of central directory record" in ZIP64 files.
 270          */
 271         function readZip64EndOfCentralDirectoryRecord() {
 272                 if ( $this->eocdr64Locator['eocdr64 start disk'] != 0
 273                         || $this->eocdr64Locator['number of disks'] != 0
 274                 ) {
 275                         $this->error( 'zip-unsupported', 'more than one disk (in EOCDR64 locator)' );
 276                 }
 277
 278                 $info = array(
 279                         'signature' => array( 'string', 4 ),
 280                         'EOCDR64 size' => 8,
 281                         'version made by' => 2,
 282                         'version needed' => 2,
 283                         'disk' => 4,
 284                         'CD start disk' => 4,
 285                         'CD entries this disk' => 8,
 286                         'CD entries total' => 8,
 287                         'CD size' => 8,
 288                         'CD offset' => 8
 289                 );
 290                 $structSize = $this->getStructSize( $info );
 291                 $block = $this->getBlock( $this->eocdr64Locator['eocdr64 offset'], $structSize );
 292                 $this->eocdr64 = $data = $this->unpack( $block, $info );
 293                 if ( $data['signature'] !== "PK\x06\x06" ) {
 294                         $this->error( 'zip-bad', 'wrong signature on Zip64 end of central directory record' );
 295                 }
 296                 if ( $data['disk'] !== 0
 297                         || $data['CD start disk'] !== 0
 298                 ) {
 299                         $this->error( 'zip-unsupported', 'more than one disk (in EOCDR64)' );
 300                 }
 301         }
 302
 303         /**
 304          * Find the location of the central directory, as would be seen by a
 305          * non-ZIP64 reader.
 306          *
 307          * @return array List containing offset, size and end position.
 308          */
 309         function findOldCentralDirectory() {
 310                 $size = $this->eocdr['CD size'];
 311                 $offset = $this->eocdr['CD offset'];
 312                 $endPos = $this->eocdr['position'];
 313
 314                 // Some readers use the EOCDR position instead of the offset field
 315                 // to find the directory, so to be safe, we check if they both agree.
 316                 if ( $offset + $size != $endPos ) {
 317                         $this->error( 'zip-bad', 'the central directory does not immediately precede the end ' .
 318                                 'of central directory record' );
 319                 }
 320
 321                 return array( $offset, $size );
 322         }
 323
 324         /**
 325          * Find the location of the central directory, as would be seen by a
 326          * ZIP64-compliant reader.
 327          *
 328          * @return array List containing offset, size and end position.
 329          */
 330         function findZip64CentralDirectory() {
 331                 // The spec is ambiguous about the exact rules of precedence between the
 332                 // ZIP64 headers and the original headers. Here we follow zip_util.c
 333                 // from OpenJDK 7.
 334                 $size = $this->eocdr['CD size'];
 335                 $offset = $this->eocdr['CD offset'];
 336                 $numEntries = $this->eocdr['CD entries total'];
 337                 $endPos = $this->eocdr['position'];
 338                 if ( $size == 0xffffffff
 339                         || $offset == 0xffffffff
 340                         || $numEntries == 0xffff
 341                 ) {
 342                         $this->readZip64EndOfCentralDirectoryLocator();
 343
 344                         if ( isset( $this->eocdr64Locator['eocdr64 offset'] ) ) {
 345                                 $this->readZip64EndOfCentralDirectoryRecord();
 346                                 if ( isset( $this->eocdr64['CD offset'] ) ) {
 347                                         $size = $this->eocdr64['CD size'];
 348                                         $offset = $this->eocdr64['CD offset'];
 349                                         $endPos = $this->eocdr64Locator['eocdr64 offset'];
 350                                 }
 351                         }
 352                 }
 353                 // Some readers use the EOCDR position instead of the offset field
 354                 // to find the directory, so to be safe, we check if they both agree.
 355                 if ( $offset + $size != $endPos ) {
 356                         $this->error( 'zip-bad', 'the central directory does not immediately precede the end ' .
 357                                 'of central directory record' );
 358                 }
 359
 360                 return array( $offset, $size );
 361         }
 362
 363         /**
 364          * Read the central directory at the given location
 365          * @param int $offset
 366          * @param int $size
 367          */
 368         function readCentralDirectory( $offset, $size ) {
 369                 $block = $this->getBlock( $offset, $size );
 370
 371                 $fixedInfo = array(
 372                         'signature' => array( 'string', 4 ),
 373                         'version made by' => 2,
 374                         'version needed' => 2,
 375                         'general bits' => 2,
 376                         'compression method' => 2,
 377                         'mod time' => 2,
 378                         'mod date' => 2,
 379                         'crc-32' => 4,
 380                         'compressed size' => 4,
 381                         'uncompressed size' => 4,
 382                         'name length' => 2,
 383                         'extra field length' => 2,
 384                         'comment length' => 2,
 385                         'disk number start' => 2,
 386                         'internal attrs' => 2,
 387                         'external attrs' => 4,
 388                         'local header offset' => 4,
 389                 );
 390                 $fixedSize = $this->getStructSize( $fixedInfo );
 391
 392                 $pos = 0;
 393                 while ( $pos < $size ) {
 394                         $data = $this->unpack( $block, $fixedInfo, $pos );
 395                         $pos += $fixedSize;
 396
 397                         if ( $data['signature'] !== "PK\x01\x02" ) {
 398                                 $this->error( 'zip-bad', 'Invalid signature found in directory entry' );
 399                         }
 400
 401                         $variableInfo = array(
 402                                 'name' => array( 'string', $data['name length'] ),
 403                                 'extra field' => array( 'string', $data['extra field length'] ),
 404                                 'comment' => array( 'string', $data['comment length'] ),
 405                         );
 406                         $data += $this->unpack( $block, $variableInfo, $pos );
 407                         $pos += $this->getStructSize( $variableInfo );
 408
 409                         if ( $this->zip64 && (
 410                                         $data['compressed size'] == 0xffffffff
 411                                         || $data['uncompressed size'] == 0xffffffff
 412                                         || $data['local header offset'] == 0xffffffff )
 413                         ) {
 414                                 $zip64Data = $this->unpackZip64Extra( $data['extra field'] );
 415                                 if ( $zip64Data ) {
 416                                         $data = $zip64Data + $data;
 417                                 }
 418                         }
 419
 420                         if ( $this->testBit( $data['general bits'], self::GENERAL_CD_ENCRYPTED ) ) {
 421                                 $this->error( 'zip-unsupported', 'central directory encryption is not supported' );
 422                         }
 423
 424                         // Convert the timestamp into MediaWiki format
 425                         // For the format, please see the MS-DOS 2.0 Programmer's Reference,
 426                         // pages 3-5 and 3-6.
 427                         $time = $data['mod time'];
 428                         $date = $data['mod date'];
 429
 430                         $year = 1980 + ( $date >> 9 );
 431                         $month = ( $date >> 5 ) & 15;
 432                         $day = $date & 31;
 433                         $hour = ( $time >> 11 ) & 31;
 434                         $minute = ( $time >> 5 ) & 63;
 435                         $second = ( $time & 31 ) * 2;
 436                         $timestamp = sprintf( "%04d%02d%02d%02d%02d%02d",
 437                                 $year, $month, $day, $hour, $minute, $second );
 438
 439                         // Convert the character set in the file name
 440                         if ( $this->testBit( $data['general bits'], self::GENERAL_UTF8 ) ) {
 441                                 $name = $data['name'];
 442                         } else {
 443                                 $name = iconv( 'CP437', 'UTF-8', $data['name'] );
 444                         }
 445
 446                         // Compile a data array for the user, with a sensible format
 447                         $userData = array(
 448                                 'name' => $name,
 449                                 'mtime' => $timestamp,
 450                                 'size' => $data['uncompressed size'],
 451                         );
 452                         call_user_func( $this->callback, $userData );
 453                 }
 454         }
 455
 456         /**
 457          * Interpret ZIP64 "extra field" data and return an associative array.
 458          * @param string $extraField
 459          * @return array|bool
 460          */
 461         function unpackZip64Extra( $extraField ) {
 462                 $extraHeaderInfo = array(
 463                         'id' => 2,
 464                         'size' => 2,
 465                 );
 466                 $extraHeaderSize = $this->getStructSize( $extraHeaderInfo );
 467
 468                 $zip64ExtraInfo = array(
 469                         'uncompressed size' => 8,
 470                         'compressed size' => 8,
 471                         'local header offset' => 8,
 472                         'disk number start' => 4,
 473                 );
 474
 475                 $extraPos = 0;
 476                 while ( $extraPos < strlen( $extraField ) ) {
 477                         $extra = $this->unpack( $extraField, $extraHeaderInfo, $extraPos );
 478                         $extraPos += $extraHeaderSize;
 479                         $extra += $this->unpack( $extraField,
 480                                 array( 'data' => array( 'string', $extra['size'] ) ),
 481                                 $extraPos );
 482                         $extraPos += $extra['size'];
 483
 484                         if ( $extra['id'] == self::ZIP64_EXTRA_HEADER ) {
 485                                 return $this->unpack( $extra['data'], $zip64ExtraInfo );
 486                         }
 487                 }
 488
 489                 return false;
 490         }
 491
 492         /**
 493          * Get the length of the file.
 494          * @return int
 495          */
 496         function getFileLength() {
 497                 if ( $this->fileLength === null ) {
 498                         $stat = fstat( $this->file );
 499                         $this->fileLength = $stat['size'];
 500                 }
 501
 502                 return $this->fileLength;
 503         }
 504
 505         /**
 506          * Get the file contents from a given offset. If there are not enough bytes
 507          * in the file to satisfy the request, an exception will be thrown.
 508          *
 509          * @param int $start The byte offset of the start of the block.
 510          * @param int $length The number of bytes to return. If omitted, the remainder
 511          *    of the file will be returned.
 512          *
 513          * @return string
 514          */
 515         function getBlock( $start, $length = null ) {
 516                 $fileLength = $this->getFileLength();
 517                 if ( $start >= $fileLength ) {
 518                         $this->error( 'zip-bad', "getBlock() requested position $start, " .
 519                                 "file length is $fileLength" );
 520                 }
 521                 if ( $length === null ) {
 522                         $length = $fileLength - $start;
 523                 }
 524                 $end = $start + $length;
 525                 if ( $end > $fileLength ) {
 526                         $this->error( 'zip-bad', "getBlock() requested end position $end, " .
 527                                 "file length is $fileLength" );
 528                 }
 529                 $startSeg = floor( $start / self::SEGSIZE );
 530                 $endSeg = ceil( $end / self::SEGSIZE );
 531
 532                 $block = '';
 533                 for ( $segIndex = $startSeg; $segIndex <= $endSeg; $segIndex++ ) {
 534                         $block .= $this->getSegment( $segIndex );
 535                 }
 536
 537                 $block = substr( $block,
 538                         $start - $startSeg * self::SEGSIZE,
 539                         $length );
 540
 541                 if ( strlen( $block ) < $length ) {
 542                         $this->error( 'zip-bad', 'getBlock() returned an unexpectedly small amount of data' );
 543                 }
 544
 545                 return $block;
 546         }
 547
 548         /**
 549          * Get a section of the file starting at position $segIndex * self::SEGSIZE,
 550          * of length self::SEGSIZE. The result is cached. This is a helper function
 551          * for getBlock().
 552          *
 553          * If there are not enough bytes in the file to satisfy the request, the
 554          * return value will be truncated. If a request is made for a segment beyond
 555          * the end of the file, an empty string will be returned.
 556          *
 557          * @param int $segIndex
 558          *
 559          * @return string
 560          */
 561         function getSegment( $segIndex ) {
 562                 if ( !isset( $this->buffer[$segIndex] ) ) {
 563                         $bytePos = $segIndex * self::SEGSIZE;
 564                         if ( $bytePos >= $this->getFileLength() ) {
 565                                 $this->buffer[$segIndex] = '';
 566
 567                                 return '';
 568                         }
 569                         if ( fseek( $this->file, $bytePos ) ) {
 570                                 $this->error( 'zip-bad', "seek to $bytePos failed" );
 571                         }
 572                         $seg = fread( $this->file, self::SEGSIZE );
 573                         if ( $seg === false ) {
 574                                 $this->error( 'zip-bad', "read from $bytePos failed" );
 575                         }
 576                         $this->buffer[$segIndex] = $seg;
 577                 }
 578
 579                 return $this->buffer[$segIndex];
 580         }
 581
 582         /**
 583          * Get the size of a structure in bytes. See unpack() for the format of $struct.
 584          * @param array $struct
 585          * @return int
 586          */
 587         function getStructSize( $struct ) {
 588                 $size = 0;
 589                 foreach ( $struct as $type ) {
 590                         if ( is_array( $type ) ) {
 591                                 list( , $fieldSize ) = $type;
 592                                 $size += $fieldSize;
 593                         } else {
 594                                 $size += $type;
 595                         }
 596                 }
 597
 598                 return $size;
 599         }
 600
 601         /**
 602          * Unpack a binary structure. This is like the built-in unpack() function
 603          * except nicer.
 604          *
 605          * @param string $string The binary data input
 606          *
 607          * @param array $struct An associative array giving structure members and their
 608          *    types. In the key is the field name. The value may be either an
 609          *    integer, in which case the field is a little-endian unsigned integer
 610          *    encoded in the given number of bytes, or an array, in which case the
 611          *    first element of the array is the type name, and the subsequent
 612          *    elements are type-dependent parameters. Only one such type is defined:
 613          *       - "string": The second array element gives the length of string.
 614          *          Not null terminated.
 615          *
 616          * @param int $offset The offset into the string at which to start unpacking.
 617          *
 618          * @throws MWException
 619          * @return array Unpacked associative array. Note that large integers in the input
 620          *    may be represented as floating point numbers in the return value, so
 621          *    the use of weak comparison is advised.
 622          */
 623         function unpack( $string, $struct, $offset = 0 ) {
 624                 $size = $this->getStructSize( $struct );
 625                 if ( $offset + $size > strlen( $string ) ) {
 626                         $this->error( 'zip-bad', 'unpack() would run past the end of the supplied string' );
 627                 }
 628
 629                 $data = array();
 630                 $pos = $offset;
 631                 foreach ( $struct as $key => $type ) {
 632                         if ( is_array( $type ) ) {
 633                                 list( $typeName, $fieldSize ) = $type;
 634                                 switch ( $typeName ) {
 635                                         case 'string':
 636                                                 $data[$key] = substr( $string, $pos, $fieldSize );
 637                                                 $pos += $fieldSize;
 638                                                 break;
 639                                         default:
 640                                                 throw new MWException( __METHOD__ . ": invalid type \"$typeName\"" );
 641                                 }
 642                         } else {
 643                                 // Unsigned little-endian integer
 644                                 $length = intval( $type );
 645
 646                                 // Calculate the value. Use an algorithm which automatically
 647                                 // upgrades the value to floating point if necessary.
 648                                 $value = 0;
 649                                 for ( $i = $length - 1; $i >= 0; $i-- ) {
 650                                         $value *= 256;
 651                                         $value += ord( $string[$pos + $i] );
 652                                 }
 653
 654                                 // Throw an exception if there was loss of precision
 655                                 if ( $value > pow( 2, 52 ) ) {
 656                                         $this->error( 'zip-unsupported', 'number too large to be stored in a double. ' .
 657                                                 'This could happen if we tried to unpack a 64-bit structure ' .
 658                                                 'at an invalid location.' );
 659                                 }
 660                                 $data[$key] = $value;
 661                                 $pos += $length;
 662                         }
 663                 }
 664
 665                 return $data;
 666         }
 667
 668         /**
 669          * Returns a bit from a given position in an integer value, converted to
 670          * boolean.
 671          *
 672          * @param int $value
 673          * @param int $bitIndex The index of the bit, where 0 is the LSB.
 674          * @return bool
 675          */
 676         function testBit( $value, $bitIndex ) {
 677                 return (bool)( ( $value >> $bitIndex ) & 1 );
 678         }
 679
 680         /**
 681          * Debugging helper function which dumps a string in hexdump -C format.
 682          * @param string $s
 683          */
 684         function hexDump( $s ) {
 685                 $n = strlen( $s );
 686                 for ( $i = 0; $i < $n; $i += 16 ) {
 687                         printf( "%08X ", $i );
 688                         for ( $j = 0; $j < 16; $j++ ) {
 689                                 print " ";
 690                                 if ( $j == 8 ) {
 691                                         print " ";
 692                                 }
 693                                 if ( $i + $j >= $n ) {
 694                                         print "  ";
 695                                 } else {
 696                                         printf( "%02X", ord( $s[$i + $j] ) );
 697                                 }
 698                         }
 699
 700                         print "  |";
 701                         for ( $j = 0; $j < 16; $j++ ) {
 702                                 if ( $i + $j >= $n ) {
 703                                         print " ";
 704                                 } elseif ( ctype_print( $s[$i + $j] ) ) {
 705                                         print $s[$i + $j];
 706                                 } else {
 707                                         print '.';
 708                                 }
 709                         }
 710                         print "|\n";
 711                 }
 712         }
 713 }
 714
 715 /**
 716  * Internal exception class. Will be caught by private code.
 717  */
 718 class ZipDirectoryReaderError extends Exception {
 719         protected $errorCode;
 720
 721         function __construct( $code ) {
 722                 $this->errorCode = $code;
 723                 parent::__construct( "ZipDirectoryReader error: $code" );
 724         }
 725
 726         /**
 727          * @return mixed
 728          */
 729         function getErrorCode() {
 730                 return $this->errorCode;
 731         }
 732 }