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