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          * @throws ZipDirectoryReaderError
 190          */
 191         function error( $code, $debugMessage ) {
 192                 wfDebug( __CLASS__ . ": Fatal error: $debugMessage\n" );
 193                 throw new ZipDirectoryReaderError( $code );
 194         }
 195
 196         /**
 197          * Read the header which is at the end of the central directory,
 198          * unimaginatively called the "end of central directory record" by the ZIP
 199          * spec.
 200          */
 201         function readEndOfCentralDirectoryRecord() {
 202                 $info = array(
 203                         'signature' => 4,
 204                         'disk' => 2,
 205                         'CD start disk' => 2,
 206                         'CD entries this disk' => 2,
 207                         'CD entries total' => 2,
 208                         'CD size' => 4,
 209                         'CD offset' => 4,
 210                         'file comment length' => 2,
 211                 );
 212                 $structSize = $this->getStructSize( $info );
 213                 $startPos = $this->getFileLength() - 65536 - $structSize;
 214                 if ( $startPos < 0 ) {
 215                         $startPos = 0;
 216                 }
 217
 218                 $block = $this->getBlock( $startPos );
 219                 $sigPos = strrpos( $block, "PK\x05\x06" );
 220                 if ( $sigPos === false ) {
 221                         $this->error( 'zip-wrong-format',
 222                                 "zip file lacks EOCDR signature. It probably isn't a zip file." );
 223                 }
 224
 225                 $this->eocdr = $this->unpack( substr( $block, $sigPos ), $info );
 226                 $this->eocdr['EOCDR size'] = $structSize + $this->eocdr['file comment length'];
 227
 228                 if ( $structSize + $this->eocdr['file comment length'] != strlen( $block ) - $sigPos ) {
 229                         $this->error( 'zip-bad', 'trailing bytes after the end of the file comment' );
 230                 }
 231                 if ( $this->eocdr['disk'] !== 0
 232                         || $this->eocdr['CD start disk'] !== 0
 233                 ) {
 234                         $this->error( 'zip-unsupported', 'more than one disk (in EOCDR)' );
 235                 }
 236                 $this->eocdr += $this->unpack(
 237                         $block,
 238                         array( 'file comment' => array( 'string', $this->eocdr['file comment length'] ) ),
 239                         $sigPos + $structSize );
 240                 $this->eocdr['position'] = $startPos + $sigPos;
 241         }
 242
 243         /**
 244          * Read the header called the "ZIP64 end of central directory locator". An
 245          * error will be raised if it does not exist.
 246          */
 247         function readZip64EndOfCentralDirectoryLocator() {
 248                 $info = array(
 249                         'signature' => array( 'string', 4 ),
 250                         'eocdr64 start disk' => 4,
 251                         'eocdr64 offset' => 8,
 252                         'number of disks' => 4,
 253                 );
 254                 $structSize = $this->getStructSize( $info );
 255
 256                 $start = $this->getFileLength() - $this->eocdr['EOCDR size'] - $structSize;
 257                 $block = $this->getBlock( $start, $structSize );
 258                 $this->eocdr64Locator = $data = $this->unpack( $block, $info );
 259
 260                 if ( $data['signature'] !== "PK\x06\x07" ) {
 261                         // Note: Java will allow this and continue to read the
 262                         // EOCDR64, so we have to reject the upload, we can't
 263                         // just use the EOCDR header instead.
 264                         $this->error( 'zip-bad', 'wrong signature on Zip64 end of central directory locator' );
 265                 }
 266         }
 267
 268         /**
 269          * Read the header called the "ZIP64 end of central directory record". It
 270          * may replace the regular "end of central directory record" in ZIP64 files.
 271          */
 272         function readZip64EndOfCentralDirectoryRecord() {
 273                 if ( $this->eocdr64Locator['eocdr64 start disk'] != 0
 274                         || $this->eocdr64Locator['number of disks'] != 0
 275                 ) {
 276                         $this->error( 'zip-unsupported', 'more than one disk (in EOCDR64 locator)' );
 277                 }
 278
 279                 $info = array(
 280                         'signature' => array( 'string', 4 ),
 281                         'EOCDR64 size' => 8,
 282                         'version made by' => 2,
 283                         'version needed' => 2,
 284                         'disk' => 4,
 285                         'CD start disk' => 4,
 286                         'CD entries this disk' => 8,
 287                         'CD entries total' => 8,
 288                         'CD size' => 8,
 289                         'CD offset' => 8
 290                 );
 291                 $structSize = $this->getStructSize( $info );
 292                 $block = $this->getBlock( $this->eocdr64Locator['eocdr64 offset'], $structSize );
 293                 $this->eocdr64 = $data = $this->unpack( $block, $info );
 294                 if ( $data['signature'] !== "PK\x06\x06" ) {
 295                         $this->error( 'zip-bad', 'wrong signature on Zip64 end of central directory record' );
 296                 }
 297                 if ( $data['disk'] !== 0
 298                         || $data['CD start disk'] !== 0
 299                 ) {
 300                         $this->error( 'zip-unsupported', 'more than one disk (in EOCDR64)' );
 301                 }
 302         }
 303
 304         /**
 305          * Find the location of the central directory, as would be seen by a
 306          * non-ZIP64 reader.
 307          *
 308          * @return array List containing offset, size and end position.
 309          */
 310         function findOldCentralDirectory() {
 311                 $size = $this->eocdr['CD size'];
 312                 $offset = $this->eocdr['CD offset'];
 313                 $endPos = $this->eocdr['position'];
 314
 315                 // Some readers use the EOCDR position instead of the offset field
 316                 // to find the directory, so to be safe, we check if they both agree.
 317                 if ( $offset + $size != $endPos ) {
 318                         $this->error( 'zip-bad', 'the central directory does not immediately precede the end ' .
 319                                 'of central directory record' );
 320                 }
 321
 322                 return array( $offset, $size );
 323         }
 324
 325         /**
 326          * Find the location of the central directory, as would be seen by a
 327          * ZIP64-compliant reader.
 328          *
 329          * @return array List containing offset, size and end position.
 330          */
 331         function findZip64CentralDirectory() {
 332                 // The spec is ambiguous about the exact rules of precedence between the
 333                 // ZIP64 headers and the original headers. Here we follow zip_util.c
 334                 // from OpenJDK 7.
 335                 $size = $this->eocdr['CD size'];
 336                 $offset = $this->eocdr['CD offset'];
 337                 $numEntries = $this->eocdr['CD entries total'];
 338                 $endPos = $this->eocdr['position'];
 339                 if ( $size == 0xffffffff
 340                         || $offset == 0xffffffff
 341                         || $numEntries == 0xffff
 342                 ) {
 343                         $this->readZip64EndOfCentralDirectoryLocator();
 344
 345                         if ( isset( $this->eocdr64Locator['eocdr64 offset'] ) ) {
 346                                 $this->readZip64EndOfCentralDirectoryRecord();
 347                                 if ( isset( $this->eocdr64['CD offset'] ) ) {
 348                                         $size = $this->eocdr64['CD size'];
 349                                         $offset = $this->eocdr64['CD offset'];
 350                                         $endPos = $this->eocdr64Locator['eocdr64 offset'];
 351                                 }
 352                         }
 353                 }
 354                 // Some readers use the EOCDR position instead of the offset field
 355                 // to find the directory, so to be safe, we check if they both agree.
 356                 if ( $offset + $size != $endPos ) {
 357                         $this->error( 'zip-bad', 'the central directory does not immediately precede the end ' .
 358                                 'of central directory record' );
 359                 }
 360
 361                 return array( $offset, $size );
 362         }
 363
 364         /**
 365          * Read the central directory at the given location
 366          * @param int $offset
 367          * @param int $size
 368          */
 369         function readCentralDirectory( $offset, $size ) {
 370                 $block = $this->getBlock( $offset, $size );
 371
 372                 $fixedInfo = array(
 373                         'signature' => array( 'string', 4 ),
 374                         'version made by' => 2,
 375                         'version needed' => 2,
 376                         'general bits' => 2,
 377                         'compression method' => 2,
 378                         'mod time' => 2,
 379                         'mod date' => 2,
 380                         'crc-32' => 4,
 381                         'compressed size' => 4,
 382                         'uncompressed size' => 4,
 383                         'name length' => 2,
 384                         'extra field length' => 2,
 385                         'comment length' => 2,
 386                         'disk number start' => 2,
 387                         'internal attrs' => 2,
 388                         'external attrs' => 4,
 389                         'local header offset' => 4,
 390                 );
 391                 $fixedSize = $this->getStructSize( $fixedInfo );
 392
 393                 $pos = 0;
 394                 while ( $pos < $size ) {
 395                         $data = $this->unpack( $block, $fixedInfo, $pos );
 396                         $pos += $fixedSize;
 397
 398                         if ( $data['signature'] !== "PK\x01\x02" ) {
 399                                 $this->error( 'zip-bad', 'Invalid signature found in directory entry' );
 400                         }
 401
 402                         $variableInfo = array(
 403                                 'name' => array( 'string', $data['name length'] ),
 404                                 'extra field' => array( 'string', $data['extra field length'] ),
 405                                 'comment' => array( 'string', $data['comment length'] ),
 406                         );
 407                         $data += $this->unpack( $block, $variableInfo, $pos );
 408                         $pos += $this->getStructSize( $variableInfo );
 409
 410                         if ( $this->zip64 && (
 411                                         $data['compressed size'] == 0xffffffff
 412                                         || $data['uncompressed size'] == 0xffffffff
 413                                         || $data['local header offset'] == 0xffffffff )
 414                         ) {
 415                                 $zip64Data = $this->unpackZip64Extra( $data['extra field'] );
 416                                 if ( $zip64Data ) {
 417                                         $data = $zip64Data + $data;
 418                                 }
 419                         }
 420
 421                         if ( $this->testBit( $data['general bits'], self::GENERAL_CD_ENCRYPTED ) ) {
 422                                 $this->error( 'zip-unsupported', 'central directory encryption is not supported' );
 423                         }
 424
 425                         // Convert the timestamp into MediaWiki format
 426                         // For the format, please see the MS-DOS 2.0 Programmer's Reference,
 427                         // pages 3-5 and 3-6.
 428                         $time = $data['mod time'];
 429                         $date = $data['mod date'];
 430
 431                         $year = 1980 + ( $date >> 9 );
 432                         $month = ( $date >> 5 ) & 15;
 433                         $day = $date & 31;
 434                         $hour = ( $time >> 11 ) & 31;
 435                         $minute = ( $time >> 5 ) & 63;
 436                         $second = ( $time & 31 ) * 2;
 437                         $timestamp = sprintf( "%04d%02d%02d%02d%02d%02d",
 438                                 $year, $month, $day, $hour, $minute, $second );
 439
 440                         // Convert the character set in the file name
 441                         if ( $this->testBit( $data['general bits'], self::GENERAL_UTF8 ) ) {
 442                                 $name = $data['name'];
 443                         } else {
 444                                 $name = iconv( 'CP437', 'UTF-8', $data['name'] );
 445                         }
 446
 447                         // Compile a data array for the user, with a sensible format
 448                         $userData = array(
 449                                 'name' => $name,
 450                                 'mtime' => $timestamp,
 451                                 'size' => $data['uncompressed size'],
 452                         );
 453                         call_user_func( $this->callback, $userData );
 454                 }
 455         }
 456
 457         /**
 458          * Interpret ZIP64 "extra field" data and return an associative array.
 459          * @param string $extraField
 460          * @return array|bool
 461          */
 462         function unpackZip64Extra( $extraField ) {
 463                 $extraHeaderInfo = array(
 464                         'id' => 2,
 465                         'size' => 2,
 466                 );
 467                 $extraHeaderSize = $this->getStructSize( $extraHeaderInfo );
 468
 469                 $zip64ExtraInfo = array(
 470                         'uncompressed size' => 8,
 471                         'compressed size' => 8,
 472                         'local header offset' => 8,
 473                         'disk number start' => 4,
 474                 );
 475
 476                 $extraPos = 0;
 477                 while ( $extraPos < strlen( $extraField ) ) {
 478                         $extra = $this->unpack( $extraField, $extraHeaderInfo, $extraPos );
 479                         $extraPos += $extraHeaderSize;
 480                         $extra += $this->unpack( $extraField,
 481                                 array( 'data' => array( 'string', $extra['size'] ) ),
 482                                 $extraPos );
 483                         $extraPos += $extra['size'];
 484
 485                         if ( $extra['id'] == self::ZIP64_EXTRA_HEADER ) {
 486                                 return $this->unpack( $extra['data'], $zip64ExtraInfo );
 487                         }
 488                 }
 489
 490                 return false;
 491         }
 492
 493         /**
 494          * Get the length of the file.
 495          * @return int
 496          */
 497         function getFileLength() {
 498                 if ( $this->fileLength === null ) {
 499                         $stat = fstat( $this->file );
 500                         $this->fileLength = $stat['size'];
 501                 }
 502
 503                 return $this->fileLength;
 504         }
 505
 506         /**
 507          * Get the file contents from a given offset. If there are not enough bytes
 508          * in the file to satisfy the request, an exception will be thrown.
 509          *
 510          * @param int $start The byte offset of the start of the block.
 511          * @param int $length The number of bytes to return. If omitted, the remainder
 512          *    of the file will be returned.
 513          *
 514          * @return string
 515          */
 516         function getBlock( $start, $length = null ) {
 517                 $fileLength = $this->getFileLength();
 518                 if ( $start >= $fileLength ) {
 519                         $this->error( 'zip-bad', "getBlock() requested position $start, " .
 520                                 "file length is $fileLength" );
 521                 }
 522                 if ( $length === null ) {
 523                         $length = $fileLength - $start;
 524                 }
 525                 $end = $start + $length;
 526                 if ( $end > $fileLength ) {
 527                         $this->error( 'zip-bad', "getBlock() requested end position $end, " .
 528                                 "file length is $fileLength" );
 529                 }
 530                 $startSeg = floor( $start / self::SEGSIZE );
 531                 $endSeg = ceil( $end / self::SEGSIZE );
 532
 533                 $block = '';
 534                 for ( $segIndex = $startSeg; $segIndex <= $endSeg; $segIndex++ ) {
 535                         $block .= $this->getSegment( $segIndex );
 536                 }
 537
 538                 $block = substr( $block,
 539                         $start - $startSeg * self::SEGSIZE,
 540                         $length );
 541
 542                 if ( strlen( $block ) < $length ) {
 543                         $this->error( 'zip-bad', 'getBlock() returned an unexpectedly small amount of data' );
 544                 }
 545
 546                 return $block;
 547         }
 548
 549         /**
 550          * Get a section of the file starting at position $segIndex * self::SEGSIZE,
 551          * of length self::SEGSIZE. The result is cached. This is a helper function
 552          * for getBlock().
 553          *
 554          * If there are not enough bytes in the file to satisfy the request, the
 555          * return value will be truncated. If a request is made for a segment beyond
 556          * the end of the file, an empty string will be returned.
 557          *
 558          * @param int $segIndex
 559          *
 560          * @return string
 561          */
 562         function getSegment( $segIndex ) {
 563                 if ( !isset( $this->buffer[$segIndex] ) ) {
 564                         $bytePos = $segIndex * self::SEGSIZE;
 565                         if ( $bytePos >= $this->getFileLength() ) {
 566                                 $this->buffer[$segIndex] = '';
 567
 568                                 return '';
 569                         }
 570                         if ( fseek( $this->file, $bytePos ) ) {
 571                                 $this->error( 'zip-bad', "seek to $bytePos failed" );
 572                         }
 573                         $seg = fread( $this->file, self::SEGSIZE );
 574                         if ( $seg === false ) {
 575                                 $this->error( 'zip-bad', "read from $bytePos failed" );
 576                         }
 577                         $this->buffer[$segIndex] = $seg;
 578                 }
 579
 580                 return $this->buffer[$segIndex];
 581         }
 582
 583         /**
 584          * Get the size of a structure in bytes. See unpack() for the format of $struct.
 585          * @param array $struct
 586          * @return int
 587          */
 588         function getStructSize( $struct ) {
 589                 $size = 0;
 590                 foreach ( $struct as $type ) {
 591                         if ( is_array( $type ) ) {
 592                                 list( , $fieldSize ) = $type;
 593                                 $size += $fieldSize;
 594                         } else {
 595                                 $size += $type;
 596                         }
 597                 }
 598
 599                 return $size;
 600         }
 601
 602         /**
 603          * Unpack a binary structure. This is like the built-in unpack() function
 604          * except nicer.
 605          *
 606          * @param string $string The binary data input
 607          *
 608          * @param array $struct An associative array giving structure members and their
 609          *    types. In the key is the field name. The value may be either an
 610          *    integer, in which case the field is a little-endian unsigned integer
 611          *    encoded in the given number of bytes, or an array, in which case the
 612          *    first element of the array is the type name, and the subsequent
 613          *    elements are type-dependent parameters. Only one such type is defined:
 614          *       - "string": The second array element gives the length of string.
 615          *          Not null terminated.
 616          *
 617          * @param int $offset The offset into the string at which to start unpacking.
 618          *
 619          * @throws MWException
 620          * @return array Unpacked associative array. Note that large integers in the input
 621          *    may be represented as floating point numbers in the return value, so
 622          *    the use of weak comparison is advised.
 623          */
 624         function unpack( $string, $struct, $offset = 0 ) {
 625                 $size = $this->getStructSize( $struct );
 626                 if ( $offset + $size > strlen( $string ) ) {
 627                         $this->error( 'zip-bad', 'unpack() would run past the end of the supplied string' );
 628                 }
 629
 630                 $data = array();
 631                 $pos = $offset;
 632                 foreach ( $struct as $key => $type ) {
 633                         if ( is_array( $type ) ) {
 634                                 list( $typeName, $fieldSize ) = $type;
 635                                 switch ( $typeName ) {
 636                                         case 'string':
 637                                                 $data[$key] = substr( $string, $pos, $fieldSize );
 638                                                 $pos += $fieldSize;
 639                                                 break;
 640                                         default:
 641                                                 throw new MWException( __METHOD__ . ": invalid type \"$typeName\"" );
 642                                 }
 643                         } else {
 644                                 // Unsigned little-endian integer
 645                                 $length = intval( $type );
 646
 647                                 // Calculate the value. Use an algorithm which automatically
 648                                 // upgrades the value to floating point if necessary.
 649                                 $value = 0;
 650                                 for ( $i = $length - 1; $i >= 0; $i-- ) {
 651                                         $value *= 256;
 652                                         $value += ord( $string[$pos + $i] );
 653                                 }
 654
 655                                 // Throw an exception if there was loss of precision
 656                                 if ( $value > pow( 2, 52 ) ) {
 657                                         $this->error( 'zip-unsupported', 'number too large to be stored in a double. ' .
 658                                                 'This could happen if we tried to unpack a 64-bit structure ' .
 659                                                 'at an invalid location.' );
 660                                 }
 661                                 $data[$key] = $value;
 662                                 $pos += $length;
 663                         }
 664                 }
 665
 666                 return $data;
 667         }
 668
 669         /**
 670          * Returns a bit from a given position in an integer value, converted to
 671          * boolean.
 672          *
 673          * @param int $value
 674          * @param int $bitIndex The index of the bit, where 0 is the LSB.
 675          * @return bool
 676          */
 677         function testBit( $value, $bitIndex ) {
 678                 return (bool)( ( $value >> $bitIndex ) & 1 );
 679         }
 680
 681         /**
 682          * Debugging helper function which dumps a string in hexdump -C format.
 683          * @param string $s
 684          */
 685         function hexDump( $s ) {
 686                 $n = strlen( $s );
 687                 for ( $i = 0; $i < $n; $i += 16 ) {
 688                         printf( "%08X ", $i );
 689                         for ( $j = 0; $j < 16; $j++ ) {
 690                                 print " ";
 691                                 if ( $j == 8 ) {
 692                                         print " ";
 693                                 }
 694                                 if ( $i + $j >= $n ) {
 695                                         print "  ";
 696                                 } else {
 697                                         printf( "%02X", ord( $s[$i + $j] ) );
 698                                 }
 699                         }
 700
 701                         print "  |";
 702                         for ( $j = 0; $j < 16; $j++ ) {
 703                                 if ( $i + $j >= $n ) {
 704                                         print " ";
 705                                 } elseif ( ctype_print( $s[$i + $j] ) ) {
 706                                         print $s[$i + $j];
 707                                 } else {
 708                                         print '.';
 709                                 }
 710                         }
 711                         print "|\n";
 712                 }
 713         }
 714 }
 715
 716 /**
 717  * Internal exception class. Will be caught by private code.
 718  */
 719 class ZipDirectoryReaderError extends Exception {
 720         protected $errorCode;
 721
 722         function __construct( $code ) {
 723                 $this->errorCode = $code;
 724                 parent::__construct( "ZipDirectoryReader error: $code" );
 725         }
 726
 727         /**
 728          * @return mixed
 729          */
 730         function getErrorCode() {
 731                 return $this->errorCode;
 732         }
 733 }