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          */
 133         protected function __construct( $fileName, $callback, $options ) {
 134                 $this->fileName = $fileName;
 135                 $this->callback = $callback;
 136
 137                 if ( isset( $options['zip64'] ) ) {
 138                         $this->zip64 = $options['zip64'];
 139                 }
 140         }
 141
 142         /**
 143          * Read the directory according to settings in $this.
 144          *
 145          * @return Status
 146          */
 147         function execute() {
 148                 $this->file = fopen( $this->fileName, 'r' );
 149                 $this->data = array();
 150                 if ( !$this->file ) {
 151                         return Status::newFatal( 'zip-file-open-error' );
 152                 }
 153
 154                 $status = Status::newGood();
 155                 try {
 156                         $this->readEndOfCentralDirectoryRecord();
 157                         if ( $this->zip64 ) {
 158                                 list( $offset, $size ) = $this->findZip64CentralDirectory();
 159                                 $this->readCentralDirectory( $offset, $size );
 160                         } else {
 161                                 if ( $this->eocdr['CD size'] == 0xffffffff
 162                                         || $this->eocdr['CD offset'] == 0xffffffff
 163                                         || $this->eocdr['CD entries total'] == 0xffff
 164                                 ) {
 165                                         $this->error( 'zip-unsupported', 'Central directory header indicates ZIP64, ' .
 166                                                 'but we are in legacy mode. Rejecting this upload is necessary to avoid ' .
 167                                                 'opening vulnerabilities on clients using OpenJDK 7 or later.' );
 168                                 }
 169
 170                                 list( $offset, $size ) = $this->findOldCentralDirectory();
 171                                 $this->readCentralDirectory( $offset, $size );
 172                         }
 173                 } catch ( ZipDirectoryReaderError $e ) {
 174                         $status->fatal( $e->getErrorCode() );
 175                 }
 176
 177                 fclose( $this->file );
 178
 179                 return $status;
 180         }
 181
 182         /**
 183          * Throw an error, and log a debug message
 184          * @param mixed $code
 185          * @param string $debugMessage
 186          */
 187         function error( $code, $debugMessage ) {
 188                 wfDebug( __CLASS__ . ": Fatal error: $debugMessage\n" );
 189                 throw new ZipDirectoryReaderError( $code );
 190         }
 191
 192         /**
 193          * Read the header which is at the end of the central directory,
 194          * unimaginatively called the "end of central directory record" by the ZIP
 195          * spec.
 196          */
 197         function readEndOfCentralDirectoryRecord() {
 198                 $info = array(
 199                         'signature' => 4,
 200                         'disk' => 2,
 201                         'CD start disk' => 2,
 202                         'CD entries this disk' => 2,
 203                         'CD entries total' => 2,
 204                         'CD size' => 4,
 205                         'CD offset' => 4,
 206                         'file comment length' => 2,
 207                 );
 208                 $structSize = $this->getStructSize( $info );
 209                 $startPos = $this->getFileLength() - 65536 - $structSize;
 210                 if ( $startPos < 0 ) {
 211                         $startPos = 0;
 212                 }
 213
 214                 $block = $this->getBlock( $startPos );
 215                 $sigPos = strrpos( $block, "PK\x05\x06" );
 216                 if ( $sigPos === false ) {
 217                         $this->error( 'zip-wrong-format',
 218                                 "zip file lacks EOCDR signature. It probably isn't a zip file." );
 219                 }
 220
 221                 $this->eocdr = $this->unpack( substr( $block, $sigPos ), $info );
 222                 $this->eocdr['EOCDR size'] = $structSize + $this->eocdr['file comment length'];
 223
 224                 if ( $structSize + $this->eocdr['file comment length'] != strlen( $block ) - $sigPos ) {
 225                         $this->error( 'zip-bad', 'trailing bytes after the end of the file comment' );
 226                 }
 227                 if ( $this->eocdr['disk'] !== 0
 228                         || $this->eocdr['CD start disk'] !== 0
 229                 ) {
 230                         $this->error( 'zip-unsupported', 'more than one disk (in EOCDR)' );
 231                 }
 232                 $this->eocdr += $this->unpack(
 233                         $block,
 234                         array( 'file comment' => array( 'string', $this->eocdr['file comment length'] ) ),
 235                         $sigPos + $structSize );
 236                 $this->eocdr['position'] = $startPos + $sigPos;
 237         }
 238
 239         /**
 240          * Read the header called the "ZIP64 end of central directory locator". An
 241          * error will be raised if it does not exist.
 242          */
 243         function readZip64EndOfCentralDirectoryLocator() {
 244                 $info = array(
 245                         'signature' => array( 'string', 4 ),
 246                         'eocdr64 start disk' => 4,
 247                         'eocdr64 offset' => 8,
 248                         'number of disks' => 4,
 249                 );
 250                 $structSize = $this->getStructSize( $info );
 251
 252                 $start = $this->getFileLength() - $this->eocdr['EOCDR size'] - $structSize;
 253                 $block = $this->getBlock( $start, $structSize );
 254                 $this->eocdr64Locator = $data = $this->unpack( $block, $info );
 255
 256                 if ( $data['signature'] !== "PK\x06\x07" ) {
 257                         // Note: Java will allow this and continue to read the
 258                         // EOCDR64, so we have to reject the upload, we can't
 259                         // just use the EOCDR header instead.
 260                         $this->error( 'zip-bad', 'wrong signature on Zip64 end of central directory locator' );
 261                 }
 262         }
 263
 264         /**
 265          * Read the header called the "ZIP64 end of central directory record". It
 266          * may replace the regular "end of central directory record" in ZIP64 files.
 267          */
 268         function readZip64EndOfCentralDirectoryRecord() {
 269                 if ( $this->eocdr64Locator['eocdr64 start disk'] != 0
 270                         || $this->eocdr64Locator['number of disks'] != 0
 271                 ) {
 272                         $this->error( 'zip-unsupported', 'more than one disk (in EOCDR64 locator)' );
 273                 }
 274
 275                 $info = array(
 276                         'signature' => array( 'string', 4 ),
 277                         'EOCDR64 size' => 8,
 278                         'version made by' => 2,
 279                         'version needed' => 2,
 280                         'disk' => 4,
 281                         'CD start disk' => 4,
 282                         'CD entries this disk' => 8,
 283                         'CD entries total' => 8,
 284                         'CD size' => 8,
 285                         'CD offset' => 8
 286                 );
 287                 $structSize = $this->getStructSize( $info );
 288                 $block = $this->getBlock( $this->eocdr64Locator['eocdr64 offset'], $structSize );
 289                 $this->eocdr64 = $data = $this->unpack( $block, $info );
 290                 if ( $data['signature'] !== "PK\x06\x06" ) {
 291                         $this->error( 'zip-bad', 'wrong signature on Zip64 end of central directory record' );
 292                 }
 293                 if ( $data['disk'] !== 0
 294                         || $data['CD start disk'] !== 0
 295                 ) {
 296                         $this->error( 'zip-unsupported', 'more than one disk (in EOCDR64)' );
 297                 }
 298         }
 299
 300         /**
 301          * Find the location of the central directory, as would be seen by a
 302          * non-ZIP64 reader.
 303          *
 304          * @return array List containing offset, size and end position.
 305          */
 306         function findOldCentralDirectory() {
 307                 $size = $this->eocdr['CD size'];
 308                 $offset = $this->eocdr['CD offset'];
 309                 $endPos = $this->eocdr['position'];
 310
 311                 // Some readers use the EOCDR position instead of the offset field
 312                 // to find the directory, so to be safe, we check if they both agree.
 313                 if ( $offset + $size != $endPos ) {
 314                         $this->error( 'zip-bad', 'the central directory does not immediately precede the end ' .
 315                                 'of central directory record' );
 316                 }
 317
 318                 return array( $offset, $size );
 319         }
 320
 321         /**
 322          * Find the location of the central directory, as would be seen by a
 323          * ZIP64-compliant reader.
 324          *
 325          * @return array List containing offset, size and end position.
 326          */
 327         function findZip64CentralDirectory() {
 328                 // The spec is ambiguous about the exact rules of precedence between the
 329                 // ZIP64 headers and the original headers. Here we follow zip_util.c
 330                 // from OpenJDK 7.
 331                 $size = $this->eocdr['CD size'];
 332                 $offset = $this->eocdr['CD offset'];
 333                 $numEntries = $this->eocdr['CD entries total'];
 334                 $endPos = $this->eocdr['position'];
 335                 if ( $size == 0xffffffff
 336                         || $offset == 0xffffffff
 337                         || $numEntries == 0xffff
 338                 ) {
 339                         $this->readZip64EndOfCentralDirectoryLocator();
 340
 341                         if ( isset( $this->eocdr64Locator['eocdr64 offset'] ) ) {
 342                                 $this->readZip64EndOfCentralDirectoryRecord();
 343                                 if ( isset( $this->eocdr64['CD offset'] ) ) {
 344                                         $size = $this->eocdr64['CD size'];
 345                                         $offset = $this->eocdr64['CD offset'];
 346                                         $endPos = $this->eocdr64Locator['eocdr64 offset'];
 347                                 }
 348                         }
 349                 }
 350                 // Some readers use the EOCDR position instead of the offset field
 351                 // to find the directory, so to be safe, we check if they both agree.
 352                 if ( $offset + $size != $endPos ) {
 353                         $this->error( 'zip-bad', 'the central directory does not immediately precede the end ' .
 354                                 'of central directory record' );
 355                 }
 356
 357                 return array( $offset, $size );
 358         }
 359
 360         /**
 361          * Read the central directory at the given location
 362          */
 363         function readCentralDirectory( $offset, $size ) {
 364                 $block = $this->getBlock( $offset, $size );
 365
 366                 $fixedInfo = array(
 367                         'signature' => array( 'string', 4 ),
 368                         'version made by' => 2,
 369                         'version needed' => 2,
 370                         'general bits' => 2,
 371                         'compression method' => 2,
 372                         'mod time' => 2,
 373                         'mod date' => 2,
 374                         'crc-32' => 4,
 375                         'compressed size' => 4,
 376                         'uncompressed size' => 4,
 377                         'name length' => 2,
 378                         'extra field length' => 2,
 379                         'comment length' => 2,
 380                         'disk number start' => 2,
 381                         'internal attrs' => 2,
 382                         'external attrs' => 4,
 383                         'local header offset' => 4,
 384                 );
 385                 $fixedSize = $this->getStructSize( $fixedInfo );
 386
 387                 $pos = 0;
 388                 while ( $pos < $size ) {
 389                         $data = $this->unpack( $block, $fixedInfo, $pos );
 390                         $pos += $fixedSize;
 391
 392                         if ( $data['signature'] !== "PK\x01\x02" ) {
 393                                 $this->error( 'zip-bad', 'Invalid signature found in directory entry' );
 394                         }
 395
 396                         $variableInfo = array(
 397                                 'name' => array( 'string', $data['name length'] ),
 398                                 'extra field' => array( 'string', $data['extra field length'] ),
 399                                 'comment' => array( 'string', $data['comment length'] ),
 400                         );
 401                         $data += $this->unpack( $block, $variableInfo, $pos );
 402                         $pos += $this->getStructSize( $variableInfo );
 403
 404                         if ( $this->zip64 && (
 405                                         $data['compressed size'] == 0xffffffff
 406                                         || $data['uncompressed size'] == 0xffffffff
 407                                         || $data['local header offset'] == 0xffffffff )
 408                         ) {
 409                                 $zip64Data = $this->unpackZip64Extra( $data['extra field'] );
 410                                 if ( $zip64Data ) {
 411                                         $data = $zip64Data + $data;
 412                                 }
 413                         }
 414
 415                         if ( $this->testBit( $data['general bits'], self::GENERAL_CD_ENCRYPTED ) ) {
 416                                 $this->error( 'zip-unsupported', 'central directory encryption is not supported' );
 417                         }
 418
 419                         // Convert the timestamp into MediaWiki format
 420                         // For the format, please see the MS-DOS 2.0 Programmer's Reference,
 421                         // pages 3-5 and 3-6.
 422                         $time = $data['mod time'];
 423                         $date = $data['mod date'];
 424
 425                         $year = 1980 + ( $date >> 9 );
 426                         $month = ( $date >> 5 ) & 15;
 427                         $day = $date & 31;
 428                         $hour = ( $time >> 11 ) & 31;
 429                         $minute = ( $time >> 5 ) & 63;
 430                         $second = ( $time & 31 ) * 2;
 431                         $timestamp = sprintf( "%04d%02d%02d%02d%02d%02d",
 432                                 $year, $month, $day, $hour, $minute, $second );
 433
 434                         // Convert the character set in the file name
 435                         if ( $this->testBit( $data['general bits'], self::GENERAL_UTF8 ) ) {
 436                                 $name = $data['name'];
 437                         } else {
 438                                 $name = iconv( 'CP437', 'UTF-8', $data['name'] );
 439                         }
 440
 441                         // Compile a data array for the user, with a sensible format
 442                         $userData = array(
 443                                 'name' => $name,
 444                                 'mtime' => $timestamp,
 445                                 'size' => $data['uncompressed size'],
 446                         );
 447                         call_user_func( $this->callback, $userData );
 448                 }
 449         }
 450
 451         /**
 452          * Interpret ZIP64 "extra field" data and return an associative array.
 453          * @return array|bool
 454          */
 455         function unpackZip64Extra( $extraField ) {
 456                 $extraHeaderInfo = array(
 457                         'id' => 2,
 458                         'size' => 2,
 459                 );
 460                 $extraHeaderSize = $this->getStructSize( $extraHeaderInfo );
 461
 462                 $zip64ExtraInfo = array(
 463                         'uncompressed size' => 8,
 464                         'compressed size' => 8,
 465                         'local header offset' => 8,
 466                         'disk number start' => 4,
 467                 );
 468
 469                 $extraPos = 0;
 470                 while ( $extraPos < strlen( $extraField ) ) {
 471                         $extra = $this->unpack( $extraField, $extraHeaderInfo, $extraPos );
 472                         $extraPos += $extraHeaderSize;
 473                         $extra += $this->unpack( $extraField,
 474                                 array( 'data' => array( 'string', $extra['size'] ) ),
 475                                 $extraPos );
 476                         $extraPos += $extra['size'];
 477
 478                         if ( $extra['id'] == self::ZIP64_EXTRA_HEADER ) {
 479                                 return $this->unpack( $extra['data'], $zip64ExtraInfo );
 480                         }
 481                 }
 482
 483                 return false;
 484         }
 485
 486         /**
 487          * Get the length of the file.
 488          * @return int
 489          */
 490         function getFileLength() {
 491                 if ( $this->fileLength === null ) {
 492                         $stat = fstat( $this->file );
 493                         $this->fileLength = $stat['size'];
 494                 }
 495
 496                 return $this->fileLength;
 497         }
 498
 499         /**
 500          * Get the file contents from a given offset. If there are not enough bytes
 501          * in the file to satisfy the request, an exception will be thrown.
 502          *
 503          * @param int $start The byte offset of the start of the block.
 504          * @param int $length The number of bytes to return. If omitted, the remainder
 505          *    of the file will be returned.
 506          *
 507          * @return string
 508          */
 509         function getBlock( $start, $length = null ) {
 510                 $fileLength = $this->getFileLength();
 511                 if ( $start >= $fileLength ) {
 512                         $this->error( 'zip-bad', "getBlock() requested position $start, " .
 513                                 "file length is $fileLength" );
 514                 }
 515                 if ( $length === null ) {
 516                         $length = $fileLength - $start;
 517                 }
 518                 $end = $start + $length;
 519                 if ( $end > $fileLength ) {
 520                         $this->error( 'zip-bad', "getBlock() requested end position $end, " .
 521                                 "file length is $fileLength" );
 522                 }
 523                 $startSeg = floor( $start / self::SEGSIZE );
 524                 $endSeg = ceil( $end / self::SEGSIZE );
 525
 526                 $block = '';
 527                 for ( $segIndex = $startSeg; $segIndex <= $endSeg; $segIndex++ ) {
 528                         $block .= $this->getSegment( $segIndex );
 529                 }
 530
 531                 $block = substr( $block,
 532                         $start - $startSeg * self::SEGSIZE,
 533                         $length );
 534
 535                 if ( strlen( $block ) < $length ) {
 536                         $this->error( 'zip-bad', 'getBlock() returned an unexpectedly small amount of data' );
 537                 }
 538
 539                 return $block;
 540         }
 541
 542         /**
 543          * Get a section of the file starting at position $segIndex * self::SEGSIZE,
 544          * of length self::SEGSIZE. The result is cached. This is a helper function
 545          * for getBlock().
 546          *
 547          * If there are not enough bytes in the file to satisfy the request, the
 548          * return value will be truncated. If a request is made for a segment beyond
 549          * the end of the file, an empty string will be returned.
 550          *
 551          * @param int $segIndex
 552          *
 553          * @return string
 554          */
 555         function getSegment( $segIndex ) {
 556                 if ( !isset( $this->buffer[$segIndex] ) ) {
 557                         $bytePos = $segIndex * self::SEGSIZE;
 558                         if ( $bytePos >= $this->getFileLength() ) {
 559                                 $this->buffer[$segIndex] = '';
 560
 561                                 return '';
 562                         }
 563                         if ( fseek( $this->file, $bytePos ) ) {
 564                                 $this->error( 'zip-bad', "seek to $bytePos failed" );
 565                         }
 566                         $seg = fread( $this->file, self::SEGSIZE );
 567                         if ( $seg === false ) {
 568                                 $this->error( 'zip-bad', "read from $bytePos failed" );
 569                         }
 570                         $this->buffer[$segIndex] = $seg;
 571                 }
 572
 573                 return $this->buffer[$segIndex];
 574         }
 575
 576         /**
 577          * Get the size of a structure in bytes. See unpack() for the format of $struct.
 578          * @return int
 579          */
 580         function getStructSize( $struct ) {
 581                 $size = 0;
 582                 foreach ( $struct as $type ) {
 583                         if ( is_array( $type ) ) {
 584                                 list( , $fieldSize ) = $type;
 585                                 $size += $fieldSize;
 586                         } else {
 587                                 $size += $type;
 588                         }
 589                 }
 590
 591                 return $size;
 592         }
 593
 594         /**
 595          * Unpack a binary structure. This is like the built-in unpack() function
 596          * except nicer.
 597          *
 598          * @param string $string The binary data input
 599          *
 600          * @param array $struct An associative array giving structure members and their
 601          *    types. In the key is the field name. The value may be either an
 602          *    integer, in which case the field is a little-endian unsigned integer
 603          *    encoded in the given number of bytes, or an array, in which case the
 604          *    first element of the array is the type name, and the subsequent
 605          *    elements are type-dependent parameters. Only one such type is defined:
 606          *       - "string": The second array element gives the length of string.
 607          *          Not null terminated.
 608          *
 609          * @param int $offset The offset into the string at which to start unpacking.
 610          *
 611          * @throws MWException
 612          * @return array Unpacked associative array. Note that large integers in the input
 613          *    may be represented as floating point numbers in the return value, so
 614          *    the use of weak comparison is advised.
 615          */
 616         function unpack( $string, $struct, $offset = 0 ) {
 617                 $size = $this->getStructSize( $struct );
 618                 if ( $offset + $size > strlen( $string ) ) {
 619                         $this->error( 'zip-bad', 'unpack() would run past the end of the supplied string' );
 620                 }
 621
 622                 $data = array();
 623                 $pos = $offset;
 624                 foreach ( $struct as $key => $type ) {
 625                         if ( is_array( $type ) ) {
 626                                 list( $typeName, $fieldSize ) = $type;
 627                                 switch ( $typeName ) {
 628                                         case 'string':
 629                                                 $data[$key] = substr( $string, $pos, $fieldSize );
 630                                                 $pos += $fieldSize;
 631                                                 break;
 632                                         default:
 633                                                 throw new MWException( __METHOD__ . ": invalid type \"$typeName\"" );
 634                                 }
 635                         } else {
 636                                 // Unsigned little-endian integer
 637                                 $length = intval( $type );
 638
 639                                 // Calculate the value. Use an algorithm which automatically
 640                                 // upgrades the value to floating point if necessary.
 641                                 $value = 0;
 642                                 for ( $i = $length - 1; $i >= 0; $i-- ) {
 643                                         $value *= 256;
 644                                         $value += ord( $string[$pos + $i] );
 645                                 }
 646
 647                                 // Throw an exception if there was loss of precision
 648                                 if ( $value > pow( 2, 52 ) ) {
 649                                         $this->error( 'zip-unsupported', 'number too large to be stored in a double. ' .
 650                                                 'This could happen if we tried to unpack a 64-bit structure ' .
 651                                                 'at an invalid location.' );
 652                                 }
 653                                 $data[$key] = $value;
 654                                 $pos += $length;
 655                         }
 656                 }
 657
 658                 return $data;
 659         }
 660
 661         /**
 662          * Returns a bit from a given position in an integer value, converted to
 663          * boolean.
 664          *
 665          * @param int $value
 666          * @param int $bitIndex The index of the bit, where 0 is the LSB.
 667          * @return bool
 668          */
 669         function testBit( $value, $bitIndex ) {
 670                 return (bool)( ( $value >> $bitIndex ) & 1 );
 671         }
 672
 673         /**
 674          * Debugging helper function which dumps a string in hexdump -C format.
 675          * @param string $s
 676          */
 677         function hexDump( $s ) {
 678                 $n = strlen( $s );
 679                 for ( $i = 0; $i < $n; $i += 16 ) {
 680                         printf( "%08X ", $i );
 681                         for ( $j = 0; $j < 16; $j++ ) {
 682                                 print " ";
 683                                 if ( $j == 8 ) {
 684                                         print " ";
 685                                 }
 686                                 if ( $i + $j >= $n ) {
 687                                         print "  ";
 688                                 } else {
 689                                         printf( "%02X", ord( $s[$i + $j] ) );
 690                                 }
 691                         }
 692
 693                         print "  |";
 694                         for ( $j = 0; $j < 16; $j++ ) {
 695                                 if ( $i + $j >= $n ) {
 696                                         print " ";
 697                                 } elseif ( ctype_print( $s[$i + $j] ) ) {
 698                                         print $s[$i + $j];
 699                                 } else {
 700                                         print '.';
 701                                 }
 702                         }
 703                         print "|\n";
 704                 }
 705         }
 706 }
 707
 708 /**
 709  * Internal exception class. Will be caught by private code.
 710  */
 711 class ZipDirectoryReaderError extends Exception {
 712         protected $errorCode;
 713
 714         function __construct( $code ) {
 715                 $this->errorCode = $code;
 716                 parent::__construct( "ZipDirectoryReader error: $code" );
 717         }
 718
 719         /**
 720          * @return mixed
 721          */
 722         function getErrorCode() {
 723                 return $this->errorCode;
 724         }
 725 }